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Klaas R Westerterp

1 3

Energy Balance in Motion

Department of Human Biology

Maastricht University

Maastricht

The Netherlands

© The Author(s) 2013

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ISSN 2192-9866 ISSN 2192-9874 (electronic)

ISBN 978-3-642-34626-2 ISBN 978-3-642-34627-9 (eBook)

DOI 10.1007/978-3-642-34627-9

Springer Heidelberg New York Dordrecht London

Library of Congress Control Number: 2012953017

Man survives in an environment with a variable food supply Energy balance is maintained by adapting energy intake to changes in energy expenditure and vice versa Human energetics is introduced using an animal energetics model including growth efficiency, endurance capacity and adaptation to starvation Animal energet-ics was the starting point for assessment of energy expenditure with respirometry and doubly labelled water and of body composition with densitometry and hydrometry Examples of endurance performance in athletes and non-athletes illustrate limits in energy expenditure There is a complicated interaction between physical activity and body weight Body movement requires energy as produced by muscles Thus, there is an interaction between physical activity, body weight, body composition and energy expenditure Overweight is caused by energy intake exceeding energy expenditure The questions of how energy intake and energy expenditure adapt to each other are dealt with The evidence presented, originating from fundamental research, is translational to food production and to physical activity-induced energy expenditure in competitive sports Another obvious and relevant clinical application deals with overweight and obesity, with the increasing risk of developing diabetes, cardiovascular disease and cancer Finally, activity induced energy expenditure of modern man is put in perspective by compiling changes in activity energy expendi-ture, as derived from total energy expenditure and resting energy expenditure, over time In addition, levels of activity energy expenditure in modern Western societies are compared with those from third world countries mirroring the physical activ-ity energy expenditure in Western societies in the past Levels of physical activity expenditure of modern humans are compared with those of wild terrestrial mam-mals as well, taking into account body size and temperature effects Taken together this book shows how energy balance has been in motion over the past four decades

Preface

Dr Klaas R Westerterp is professor of Human Energetics in the Faculty of Health, Medicine and Life Sciences at Maastricht University, The Netherlands His M.Sc in Biology at the University of Groningen resulted in a thesis titled ‘The energy budget of the nesting Starling, a field study’ He received a grant from the Netherlands Organisation for Scientific Research (FUNGO, NWO) for his doctorate research

in the Faculty of Mathematics and Natural Sciences

at the University of Groningen His Ph.D thesis was titled ‘How rats economize, energy loss in starva-tion’ Subsequently, he performed a three-year post-doc at Stirling University in Scotland supported

by a grant from the Natural Environment Research Council (NERC), and a two-year postdoc at the University of Groningen and the Netherlands Institute of Ecology (NIOO, KNAW) with a grant from the Netherlands Organisation for Scientific Research (BION, NWO) in order to work on flight ener-getics in birds In 1982, he became senior lecturer and subsequently full professor

at Maastricht University in the Department of Human Biology Here, his field of expertise is energy metabolism, physical activity, food intake and body composition and energy balance under controlled conditions and in daily life He was editor in chief of the Proceedings of the Nutrition Society and he is currently a member of the Editorial Board of the journal Nutrition and Metabolism (London) and of the European Journal of Clinical Nutrition, and editor in chief of the European Journal

of Applied Physiology

About the Author

The content of this book is based on work performed with many students and colleagues as reflected in the references Paul Schoffelen and Loek Wouters tech-nically supported measurements on energy expenditure with respirometry and doubly labelled water Margriet Westerterp-Plantenga reviewed the subsequent drafts of the manuscript Louis Foster edited the final text

Acknowledgments

1 Introduction, Energy Balance in Animals 1

2 Energy Balance 15

3 Limits in Energy Expenditure 37

4 Energy Expenditure, Physical Activity, Body Weight and Body Composition 47

5 Extremes in Energy Intake 63

6 Body Weight 71

7 Growth, Growth Efficiency and Ageing 83

8 Modern Man in Line with Wild Mammals 91

Appendix 97

Glossary 101

References 105

Index 111 Contents

ADMR Average daily metabolic rate

AEE Activity-induced energy expenditure

ATP Adenosine triphosphate

BMR Basal metabolic rate

COPD Chronic obstructive pulmonary disease

DEE Diet-induced energy expenditure

DEXA Dual energy X-ray absorptiometry for the measurement of body

components like mineral mass

EE Energy expenditure

EG Energy deposited in the body during growth

FAO Food and agriculture organisation of the United Nations

FFM Fat-free body mass

FM Fat mass of the body

SMR Sleeping metabolic rate

TEE Total energy expenditure

Tracmor Triaxial accelerometer for movement registration

UNU United Nations University

WHO World Health Organization

Abbreviations

Abstract Man is an omnivore and originally met energy requirements by

hunt-ing and gatherhunt-ing Man evolved in an environment of feast and famine: there were periods with either a positive or negative energy balance As an introduction to human energetics, this book on energy balance in motion starts with a chapter on animal energetics How do animals survive and reproduce in an environment with

a variable food supply? The examples on animal energetics illustrate how animals grow, reproduce and survive periods of starvation It is an introduction to method-ology and basic concepts in energetics Growth efficiency of a wild bird in its nat-ural environment, here the Starling, is similar to a farm animal like the Domestic Fowl Reproductive capacity is set by foraging capacity, determined by food avail-ability and the capacity parents can produce food to the offspring Birds feeding nestlings reach an energy ceiling where daily energy expenditure is four times resting energy expenditure Starvation leads to a decrease in energy expenditure, where the largest saving on energy expenditure can be ascribed to a decrease in activity energy expenditure

Keywords  Activity  factor  •  Body  temperature  •  Doubly  labelled  water  method  •

Energy ceiling  •  Gross energy intake  •  Growth efficiency  •  Metabolizable energy  • Starvation

The Energy Budget of the Nestling Starling

From the late Middle Ages, nestling Starlings were harvested to prepare paté or soup As such, Starlings were a source of animal protein in a hunter and gatherer system Passerine birds have short incubation periods (12–14 days) and a nestling period of some weeks, characterized by rapid growth. The conversion ratio of food 

to energy incorporated in the growing body is high Here the energy budget of the nestling Starling is presented for the calculation of the growth efficiency of a wild animal in its natural environment The result is compared with figures for the Domestic Fowl, one of our current sources for animal protein

In the Netherlands, wild Starlings were offered artificial nest sites by ing ‘Starling pots’ against a building (Fig 1.1) Pots were made from clay with a

mount-Introduction, Energy Balance in Animals

K R Westerterp, Energy Balance in Motion, SpringerBriefs in Physiology,

DOI: 10.1007/978-3-642-34627-9_1, © The Author(s) 2013

long neck, and a hole 5 cm in diameter as entrance Pots were mounted against the wall of a house at a height of some meters with the neck horizontal. At the back, against the wall, was a hole to harvest the chicks The optimal harvest time is just before fledging, in the third week after the eggs hatch An average brood provides four to five chicks of 70 g each or about 300 g Starling Starlings prefer to breed

in colonies Thus, one can mount several pots on the same house Additionally, Starlings often start a second brood, especially when taking the chicks disturbs the first brood

The Starling (Sturnus vulgaris) is a feasible subject for a field investigation

As a hole nester readily accepting nest-boxes, a Starling colony can be founded at any convenient point bounding on pastureland for foraging The nestlings develop from hatching to fledging in 19–21 days There is close synchrony in breeding behaviour within the colony and the adults forage in the same general area allow-ing several adults to be observed at the same time, thus duplicating observations Growth efficiency, the relation between energy intake and the energy deposited in the body during growth, is assessed by measurement of the separate components of

Fig 1.1 Five ‘Starling pots’, mounted against the front of a house or pub, with somebody

inspecting from the loft (Etching Claes Janz Visscher. The village party, 1617. With permission: 

Rijksmuseum, Amsterdam)

the energy budget: food intake, rejecta, metabolizable energy, energy expenditure, and energy stored in growth (Fig 1.2) Food provides the organism with energy for maintenance, temperature regulation activity and growth Of the total incoming food energy or gross energy, a part is voided as rejecta including both faeces and urine. The remainder is commonly termed metabolizable energy. Measurements of the separate components of the energy budget of the nestling Starling are described

to illustrate the methodology and general principles of energetics (Westerterp 1973).Energy intake of the nestlings is measured by taking samples of the meals, and

by counting the total number of meals per day Meals can be sampled by the lar method Nestlings are collared with a cotton thread around the neck preventing swallowing of a meal after feeding Meals are removed after each parental visit for later analysis with regard to diet composition and energy content Depending

col-on age, nestlings can be collared for periods of col-one to three hours, between some hours after sunrise and before sunset so as not to interfere with the very first and last feedings of the day The feeding frequency can be determined by automatic counting of parental visits with an electric contact in the nest entrance Energy output in rejecta is measured by taking samples of rejecta, and by observing the production frequency of rejecta Faeces and urine are excreted together in mem-branous sacs, an adaptation enabling the parents to remove them and thus keeping the nest clean The collection of samples is a simple matter, especially after the fifth day when the nestlings automatically produce a faecal sac when handled The frequency of faecal sac production is determined by watching the parents as they carry off the glistening white faecal sacs from the nest The energy content of food and faecal samples is determined by bomb calorimetry

The first days after hatching, chicks are fed with spiders; subsequently: jackets (Tipula paludosa), earthworms (Lumbricidae), and beetle species comprise

leather-Fig 1.2 Diagrammatic representation of the energy budget of a nestling Starling (After

Wester-terp 1973)

the main dietary components. Spiders provide some 80 % metabolizable energy; whereas,  leatherjackets,  worms  and  beetles  provide  only  60  %  metabolizable energy However, Starlings cannot manage to provide sufficient high quality food like spiders to meet the increasing energy requirement of growing chicks A three-day chick weighs 20 g and consumes 14 g food per day After two weeks, body weight and food intake is tripled To meet the energy requirement of a brood of four or five chicks, the parents together collect daily some 200 g of leatherjackets, earthworms and beetles Additionally, they have to meet their own energy require-ment Nestling feeding parents have to work at their upper limit As shown in Chap 3, they perform at a similar level as one of the most demanding endurance performances in man: the Tour de France.

Metabolizable  energy,  gross  energy  intake  corrected  for  energy  loss  in rejecta, is available for body maintenance, for maintaining body temperature, physical activity and growth After hatching, chicks are brooded nearly con-stantly by one of the parents, but after a week this only happens overnight Then, parents are both foraging from sunrise to sunset and the growing chicks get more physically active in the nest. Thus initially, 50 % of the metabolizable energy goes to growth. This fraction decreases to zero just before fledging. Over the total interval from hatching to fledging, 22 % of the metabolizable energy is converted to growth, in this case in Starling This is equivalent to 14 % of the total or gross energy intake This is similar to that of 16 % for Domestic Fowl Growth efficiency, the relation between energy intake and the energy depos-ited in the body during growth, does not depend on the pattern of ontogeny but seems rather a function of the type of food Higher figures are reported for fish-eating birds

Natural selection favours individuals producing the optimal number of fertile offspring Starlings habitually lay a clutch of three to seven eggs The figures as presented above were mainly from nests with four chicks The question is whether the production of offspring is higher for a larger brood size. Is the food require-ment of a chick in a larger brood lower than in a smaller brood? The higher return in a larger brood could be a reflection of the reduced energy requirement for maintaining body temperature through huddling Comparative observations in broods ranging in size from three to seven chicks showed food intake per gram of growth to be optimal for a brood of five (Fig 1.3) A chick in a brood of five needs 10–20 % less energy to reach a given body weight at fledging than in a brood of three, a saving probably mainly based on huddling behaviour This trend does not continue with a further increase to brood size seven. Here a chick needed 5–10 % more energy Deterioration of the insulative properties of the nest in the big-gest broods might explain this Additionally, chicks in bigger broods spend more energy in activity competing for food Parents of big broods have to collect more food and tend to spend less time in nest sanitation They bring in a higher pro-portion of leatherjackets and earthworms with higher water content, causing thin rejecta, which are difficult to remove

In conclusion, growth efficiency of a wild Starling in its natural environment is similar to a farm animal like the Domestic Fowl

Foraging Limits in Free Ranging Birds

The number of offspring a bird can produce is mainly a function of food ity and foraging capacity In the Starling it was the availability of spiders, leath-erjackets, earthworms and beetles, and how much a bird can collect to feed the nestlings Additionally the parent has to meet its own energy requirement for the activity by foraging The most energy demanding activity in this situation is flying

availabil-up and down between the foraging grounds and the nest Thus, the main nant for breeding success of the chicks is the working capacity of the parents As mentioned before, nestling feeding parents reach a ceiling that caps the energetic effort an animal or human can maintain over a timeframe of days or weeks This led to the question how to measure energy expenditure in free ranging animals The method of choice was the doubly labelled water method The method was invented in 1955, was validated in laboratory rats and got its first field applica-tion in birds like racing pigeons during long distance flights It subsequently was applied for the measurement of energy expenditure in man under daily living con-ditions Nowadays, it is the gold standard for the assessment of energy require-ment of modern man Presented evidence in this book on energy balance in motion

determi-is largely based on studies where energy expenditure and physical activity determi-is tified with doubly labelled water

quan-The doubly labelled water method for the measurement of energy expenditure

is based on the discovery that oxygen in the respiratory carbon dioxide is in topic equilibrium with the oxygen in body water The technique involves enrich-ing the body water of an animal with an isotope of oxygen and an isotope of

iso-Fig 1.3 Food intake per

gram growth of a nestling

Starling in relation to brood

size (After Westerterp et al. 

1982)

hydrogen and then determining the washout kinetics of both isotopes Most of the oxygen isotope in a labelled animal is lost as water, but some is also lost as car-bon dioxide because CO2 in body fluids is in isotopic equilibrium with body water due to exchange in the bicarbonate pools The hydrogen isotope is lost as water only Thus, the washout for the oxygen isotope is faster than for the hydrogen iso-tope, and the difference represents the CO2 production The isotopes of choice are the stable, heavy, isotopes of oxygen and hydrogen, oxygen-18 (18O) and deute-rium (2H), since these avoid the need to use radioactivity and can be safely used

in any organism (Fig 1.4) Both isotopes naturally occur in drinking water and thus in body water Oxygen-18 (18O) has eight protons and ten neutrons instead

of the eight protons and eight neutrons found in normal oxygen (16O) Deuterium (2H) has one proton and one neutron instead of one neutron for normal hydro-gen (1H) ‘Normal’ water consists largely of the lighter isotopes 1H and 16O, the natural abundance for 2H is about 150 parts per million or 150 ppm and for 18O

2000 ppm Enriching the body water with doubly labelled water (2H218O) for the measurement of energy expenditure implies an increase of the background levels

as mentioned with 200–300 ppm for 18O and with 100–150 ppm for 2H The CO2

production, calculated from the subsequent difference in elimination between the two isotopes, is a measure of metabolism Carbon dioxide is produced by oxida-tion of carbohydrate, protein and fat to provide energy It can be converted to units

of energy expenditure by incorporating knowledge of the chemical composition of the food being oxidised to calculate the energy equivalent of the CO2 produced.Classic examples of free ranging birds reaching foraging limits are Hirundines

like Sand Martins (Riparia riparia), Swallows (Hirundo rustica) and House

Fig 1.4 The principle of measurement of carbon dioxide production with doubly labelled water

( 2 H218 O) After administration of water labelled with heavy oxygen ( 18 O) and heavy hydrogen ( 2 H), the two isotopes mix with the body water, where 18 O exchanges with CO2 in the bicarbo- nate pools as well Thus, the elimination rate of 2 H (K2) is a measure for water loss (rH2O) and the elimination rate of 18 O (K18) is a measure for rH2O plus carbon dioxide production (rCO2), and rCO2 = K 18 −K 2

Martins (Delichon urbica) Hirundines can stay on the wing day round, where they feed on flying insects The most extreme example is the Swift (Apus apus), it only

comes down to breed Then, they occupy a hole in a steep cliff, or nowadays often

in high buildings To get again on wing, they need a free fall of some meters, as the legs are not strong enough to take off from the ground A grounded swift dies from starvation

Here, the main example of free ranging birds reaching foraging limits is the House Martin Energy expenditure in free ranging adult House Martins was meas-ured while they were feeding nestlings Observations covered three subsequent years in a colony of some 20 nests at a farm where food supply was monitored continuously with a suction trap for insects at the same height as foraging House Martins of 10–15 m

Measuring energy expenditure with doubly labelled water required capturing birds at two time points, initially to apply the labelled water and measure the sub-sequent enrichment of the body water and again to measure the final enrichment

In practice, a parent was taken from the nest at night and injected with a weighed dose of doubly labelled water It takes about one hour for the injected water to equilibrate with the body water for a 20-g House Martin Then, blood was sampled from a leg vein for measurement of the initial isotope enrichment and the bird was replaced in the nest The next morning, birds started feeding nestlings as usual and were recaptured at the end of day or the next day for the final sampling (Fig 1.5) Experimental birds were colour marked to observe where they were foraging and how many meals were brought to the nest The disturbance through capturing, injecting water and taking blood samples is minimal Some birds, as marked with regular aluminium leg rings, were observed with doubly labelled in all subsequent years

Fig 1.5 Protocol for the doubly labelled water method to measure energy expenditure in free

ranging House Martins during the breeding season (With permission from Bryant and Westerterp 1980) Stable isotopes are introduced by intraperitoneal injection (t 1 ) The initial blood samples are taken one hour after injection and consist of six capillary tubes, together containing about 100 µl blood A similar volume of blood is collected after one or two days of free-living activities (t 2 )

Energy expenditure of an animal like the House Martin is minimal during the night, while quietly sitting on the nest, and reaches peak values during flights

up and down from the nest to the foraging area The expenditure level can be expressed by the increase with respect to the resting energy expenditure This figure, total energy expenditure divided by resting energy expenditure, is the physical activity level Total energy expenditure consists of expenditure for main-tenance, food processing and physical activity For animals like nestlings, there

is an additional component for growth The activity component is the most able Comparison between species requires a figure without dimension, or units

vari-As such, total expenditure in kJ/day can be divided by resting energy expenditure

in kJ/day Resting energy expenditure of a specific animal is determined by body size  and  composition,  age,  gender  and  body  temperature.  Dividing  total  energy expenditure by resting energy expenditure adjusts for specific subject characteris-tics It results in a dimension less figure allowing for comparison of activity levels between species, also species differing in size. A larger animal has higher resting energy expenditure than a smaller animal Total energy expenditure is higher as well, and divided by resting energy expenditure might result in a comparable activ-ity level to a smaller animal Thus, the activity level of modern man was observed

to be in line with the activity level of a mammal living in the wild (Chap 8).The first year of the study, energy expenditure in adult House Martins that were feeding their nestlings was 2.9 times resting energy expenditure The two subse-quent years, it was clearly higher with an average value of 3.9 times resting energy expenditure The first year, the breeding success in the colony was below average

It was a wet summer with temperatures below average and few insects Food ability as measured with the suction trap increased gradually during the breeding season from May to September but was systematically nearly 50 % lower in the first year compared to the two following years Thus, the performance of a bird is a function of food availability The upper limit of energy expenditure, reached during the maximum feeding rate, is around four times resting energy expenditure The activity factor of four seems to be a ceiling value (Bryant and Westerterp 1980).Subsequent observations in nestling feeding Swallows and Sand Martins resulted in values of 3.9 and 4.3 times resting energy expenditure, respectively (Westerterp and Bryant 1984) It confirms the energetic ceiling is reached at an activity factor of four Subsequent observations in nestling feeding Starlings resulted in activity factors ranging from 3.2 to 4.3 (Westerterp and Drent 1985) The value of the activity factor in Starlings varied with the daily flight time Higher flight times, i.e longer distances between foraging grounds and the nest, resulted in total daily flight times of one hour to more than two hours

avail-Based on measurements as presented above, there seems to be an energy ceiling in nature Birds feeding nestlings for several weeks, reach the observed ceiling value of four times resting energy expenditure At higher values, body weight cannot be maintained and thus performance goes down The value is derived in birds in the most active part of the year, the time they feed chicks in the nest The level is determined not only by food availability but also by the capacity parents can produce to provide the food to the nestlings The level is

similar to one of the most demanding endurance performances in man: the Tour

de France (Chap 3) Another aspect is the effect of food availability The ity factor reaches higher values in a breeding season with more food, resulting in

activ-a higher breeding success This phenomenon hactiv-as been observed in mactiv-an activ-as well People reducing food intake reduce energy expenditure as well, especially through

a reduction of physical activity (Chap 6) Finally, it is surprising a bird can reach the performance of a Tour de France athlete without using supplements like sport drinks

How Rats Economize, Energy Loss in Starvation

Energy expenditure has an upper limit but also a lower limit The lower limit is of importance under conditions where food is not available The question then is: can energy expenditure be adapted to extend survival? Adaptation of energy expendi-ture to food deprivation was studied in the laboratory rat Energy expenditure was measured by means of a balance technique and by measuring oxygen consumption and carbon dioxide production (Westerterp 1977)

In the balance technique, energy expenditure is calculated from food intake, faeces and urine production, and changes in body reserves The calculated energy requirement of a 300-g rat, kept in a metabolic cage at a comfortable room tem-perature is 2 W (Joule per second) It is the energy content of the daily food con-sumed minus the energy content of faeces and urine, as measured with bomb calorimetry During food deprivation, using body reserves covers energy expendi-ture, and animals lose weight A 300-g rat lost 100-g body weight over 11 days without food Energy expenditure over the last two days of the 11-day depriva-tion interval was only 0.8 W Here, energy expenditure was calculated from the difference in energy content of the body of sacrificed animals after nine and

11 days food deprivation Thus, reducing intake reduces energy expenditure In the extreme situation of complete food deprivation, energy expenditure went down more than 50 %, from 2.0 to 0.8 W, allowing rats to survive twice as long without food

There is a classical experiment on the effect of semi-starvation in normal-weight men with similar results, the so-called Minnesota Experiment (Keys et al 1950)

It was initiated to determine the effects of relief feeding, necessitated by the ine in occupied areas of Europe during World War II The subjects were volunteers recruited from camps of conscientious objectors They stayed in the laboratory for

fam-a 12-week bfam-aseline period, 24-weeks of semi-stfam-arvfam-ation, fam-and the first 12-weeks of rehabilitation The weight maintenance diet of 14.6 MJ/d in the baseline period was reduced to 6.6 MJ/d during semi-starvation In the 24 weeks of semi-starvation, body weight went down from an average of 69 to 53 kg At the end of the 24-week interval, subjects reached a new energy balance as body weight levelled off at the lower value (Fig 1.6) Energy expenditure equalled energy intake, i.e energy expenditure went down from 14.6 to 6.6 MJ/d, a reduction of 55 %

Mechanisms causing the adaptation of energy expenditure to food deprivation were studied by measuring oxygen consumption and carbon dioxide production in rats (6) The rats were housed individually in metabolic cages (Fig 1.7) The cages were airtight except for an inlet and outlet for ventilation and measurement of the gas exchange Energy expenditure is calculated minute by minute from oxygen consumption and carbon dioxide production In combination with measurement of food intake and physical activity, energy expenditure can be split in three compo-nents: resting energy expenditure, expenditure for food processing and expenditure for physical activity Obviously, a caged rat is not as active as a rat under free-living conditions, but it can serve as a model The 300-g rat with a total energy expenditure of 2 W, as described, had a resting energy expenditure of 1.5 W, 0.2 W for food processing and the remaining 0.3 W for physical activity Thus, the activity factor of a caged rat is 2/1.5 = 1.33 Restricting intake or complete food deprivation reduced all three components of total energy expenditure In conclu-sion, eating less reduces energy requirement through a reduction of maintenance expenditure, expenditure for food processing and expenditure for physical activity.Resting energy expenditure, the largest component, decreased through a low-ering of body temperature and through behavioural changes reducing heat loss Longer-term energy restriction also reduces resting energy expenditure through weight loss The smaller body requires lower maintenance expenditure The core temperature of a rat, as recorded with a permanently implanted thermocouple

in the heart, is on average 38° C The minimal value was 36.5° C, at dusk, just before the start of the active phase of the day for a rat as a night animal Man has

a similarly low body temperature in the early morning, just before getting up The core temperature rises as soon as one gets physically active and consumes food

Fig 1.6 Mean daily energy intake, left axis and open dots, and mean body weight, right axis

and closed dots, of 32 men during 24 weeks of semi-starvation (After Keys et al 1970)

The rat’s core temperature increased from 36.5 to 39° C A temperature that man only reaches during endurance exercise or during fever In the food deprivation experiment described, the average daily core temperature of 38° C decreased below 37° C Reduction of heat loss was reached by curling up Then, they lie down on their tail and thereby decrease their heat loss In rats, the tail, the largest furless area of the body, mediates an important part of heat exchange.

Eating less implies less food to digest and process, like for temporary age in body reserves after a meal An energy deficit during food deprivation is covered  by  mobilizing  energy  from  body  stores.  Mobilizing  energy  from  body stores instead of food consumed also saves on energy costs associated with food processing like waste production as faeces and urine Energy expenditure for food processing is a function of the quantity of food consumed It is a fraction

stor-of energy intake Energy expenditure for food processing is 10 %, for a rat on a

Fig 1.7 The metabolic cage

diet of standard laboratory food Thus, when intake matches expenditure, energy expenditure for food processing is 10 % of total energy expenditure Energy expenditure decreases by 10 % when a rat stops eating This is the same for man,

as described in Chap 5

Activity energy expenditure was calculated as total energy expenditure minus the sum of energy expenditure for food processing and resting energy expenditure

In the baseline situation, before food deprivation, total energy expenditure was

2 W, resting energy expenditure 1.5 W, expenditure for food processing 10 % of 2

or 0.2 W, and activity energy expenditure the remaining 0.3 W After 11 days food deprivation, total energy expenditure was 0.8 W, resting energy expenditure 0.7 W, expenditure for food processing 0 W, and activity energy expenditure the remain-ing 0.1 W Activities performed by the rats, as monitored with a radar system, went down by about half Animals moved less and more slowly The more than

50 % decrease of activity energy expenditure, from 0.3 to 0.1 W or to one third of the initial value, is also caused by body weight loss Weight bearing activities take less energy when body weight has gone down

Summarizing,  energy  expenditure  of  a  300-g  laboratory  rat  was  2  W  under

ad libitum food conditions Food deprivation of 11 days led to a decreased body weight of 200 g and decreased total energy expenditure to 0.8 W Resting energy expenditure decreased from 1.5 to 0.7 W Expenditure for food processing decreased from 0.2 to 0.0 W, and activity energy expenditure decreased from 0.3

to 0.1 W Activity energy expenditure showed the largest relative change This is in line with the previously mentioned Minnesota Experiment in man There, the larg-est saving on energy expenditure could be ascribed to a decrease in activity energy expenditure as well (Table 1.1) Subjects were not capable of doing anything more than hanging around The main effect of an insufficient energy intake is on physi-cal performance

Methodology and concepts as described for animal energetics were the starting point for human energetics The metabolic cage became a respiration chamber with hotel facilities Doubly labelled water was not injected but consumed as a drink

Table 1.1 Energy saved by 24 weeks semi-starvation in the Minnesota Experiment (Keys et al 1950)

at a predetermined moment in time, at the start of an endurance performance like the Tour de France, or before and after a period with an energy restricted diet to lose weight The radar system to measure physical activity in a metabolic cage was maintained in the respiration chamber Additionally, miniature accelerometers were developed for the assessment of the activity pattern under daily living conditions With the methodology, new insights were acquired in energy balance and physical activity in man In the last chapter, evidence from research in animals and man is combined under the title ‘Modern man in line with wild mammals’.

Abstract Energy balance in animals and man is a balance between

energy intake and energy expenditure for body functions and physical ity Energy expenditure determines energy requirement Energy requirement is met by energy intake When energy intake does not match energy requirement, there is a misbalance, caused by intake that is either too high or too low When intake exceeds expenditure, there is a positive energy balance and excess energy

activ-is stored in body reserves When energy intake does not meet expenditure, energy

is mobilized from body reserves Both result in a change of body weight and body composition This chapter firstly describes the assessment of energy expenditure

in man, based on the methodology as described for animals in the foregoing ter Subsequent sections describe assessment of physical activity, food intake and body composition, resulting in the assessment of energy and macronutrient bal-ance The methodology forms the basis for the insights as described in the follow-ing chapters on regulation of energy balance as a function of behaviour, growth, disease, and ageing Energy balance can be derived from the measurement of energy expenditure, food intake, and body composition The indicated method for the measurement of energy expenditure is indirect calorimetry via a venti-lated hood, respiration chamber and with the doubly labelled water method Food intake is usually assessed with self-report like a dietary recall or a dietary record Self reported food intake has important limitations and the validity is insufficient for research purposes Body composition can be calculated from body weight and body volume or total body water At a negative or positive energy balance, the deficit or excess energy is largely mobilised or stored as body fat The best long term indicator for energy balance over weeks and months is body weight and body composition With the present state of the art, disturbances of energy bal-ance are better determined by measuring energy expenditure than with measuring food intake

chap-Keywords  Accelerometry  •  Body  composition  •  Dietary  record  •  Direct  calorimetry  •  Fat-free  mass  •  Fat  mass  •  Indirect  calorimetry  •  Respiration chamber  •  Substrate utilisation  •  Ventilated hood

Energy Balance

K. R. Westerterp, Energy Balance in Motion, SpringerBriefs in Physiology,

DOI: 10.1007/978-3-642-34627-9_2, © The Author(s) 2013

Assessment of Energy Expenditure

History

The first attempts for the measurement of energy expenditure in man were formed  early  in  the  seventeenth  century.  Sanctorius  (1614)  demonstrated  how  a subject loses weight while seated in a chair suspended from a balance (Fig. 2.1). The  weight  loss  was  ascribed  to  insensible  perspiration.  In  the  end  of  the  eight-eenth century, nearly 200 years later, it was shown that he body produces energy 

per-by oxidation of carbohydrate, protein and fat as consumed in food Now, we sider insensible perspiration as more of an indicator for water lost by evaporation than for energy expenditure (Westerterp 2004). A calculation shows only a minor part of weight loss is due to energy expenditure Here, the calculation is performed for a man with an average daily energy expenditure of 12 MJ/d, completely cov-ered by glucose oxidation The body produces energy from glucose by oxidation One glucose molecule (C6H12O6) is oxidised with 6 molecules oxygen (O2) to 6 molecules of carbon dioxide (CO2) and 6 molecules of water (H2O):

con-In grams, 180 g glucose (one molecule) oxidize with 192 g oxygen to produce 

264 g carbon dioxide, 108 g water, and energy. Oxidizing one molecule of glucose provides 3 MJ energy and thus, the energy expenditure of 12 MJ/d is covered by the oxidation of four molecules glucose The body weight change due to the dif-ference between the weight of oxygen consumed and carbon dioxide produced is (4 × 192) − (4 × 264) = −288 g/day. Water loss through breathing and evapora-tion via the skin is on average one-third to two-thirds of the average daily water turnover of 3 l/d, or 1,000–2,000 g/day depending on clothing, ambient temperature and humidity The calculation shows, insensible perspiration is more a measure for water loss through evaporation than for energy expenditure

The next development in the assessment of energy expenditure was a rimeter A calorimeter is a device for measuring the heat given off by something, like burning food or faeces in a bomb calorimeter The first calorimeters for the measurement of energy expenditure measured the heat given off from an animal Lavoisier (Paris, 1780) placed a guinea pig in a wire cage surrounded by chunks 

calo-of ice As the ice melted from the animal’s body heat, the water collected below

in a container, which could be weighed The amount of melted water allowed the calculation of the heat production, 334 J/g. The calorimeter was adiabatic in that the outer space, around the ice cavity surrounding the cage, was packed with snow

to maintain a constant temperature around the inner shell, which was filled with ice The days when these measurements could be made was limited by the mild winters in Paris in a time ice machines were not yet invented The first human calorimeter  was  developed  around  1900.  Direct  calorimetry,  measuring  energy expenditure by measuring heat loss, is nowadays replaced by indirect calorimetry Living can be regarded as a combustive process The metabolism of an organism is

C6H12O6+6 O2→6 CO2+6 H2O + energy

a process of energy production by the combustion of fuel in the form of drate, protein, fat or alcohol. In this process oxygen is consumed and carbon diox-ide  produced.  Measuring  energy  expenditure  by  measuring  oxygen  consumption and/or carbon dioxide production is called indirect calorimetry.

carbohy-Fig 2.1

Sanctorius (Italy, 1561–1636) started to assess energy expenditure from weight meas-urements.  For  30  years,  he  measured  his  weight;  sitting  on  a  chair  suspended  from  a  balance, 

what he ate and drank, and produced faeces and urine He observed the weight of what he ate and drank was larger than the weight loss in faces and urine The difference was ascribed to insensi- ble perspiration

Current Methods

In  indirect  calorimetry  the  energy  production  is  calculated  from  chemical  cesses. Knowing, for example, that the oxidation of 1 mol glucose requires 6 mol oxygen  and  produces  6  mol  carbon  dioxide,  6  mol  water  and  3  MJ  energy,  the energy production can then be calculated from the oxygen consumption and car-bon dioxide production The ratio of oxygen and carbon dioxide varies with the nutrient oxidised (Table 2.1). Brouwer (1957) drew up a simple formula for calcu-lating the energy production (kJ), based on the quantities of carbohydrate (C, g), protein (P, g) and fat (F, g) oxidized, from oxygen consumption (l), carbon dioxide production (l) and urine-nitrogen loss. The principle of the calculation consists of three equations with the three measured variables:

pro-Protein  oxidation  (g)  is  calculated  as  6.25  x  urine-nitrogen  (g),  and  quently oxygen consumption and carbon dioxide production can be corrected for protein oxidation to enable the calculation of carbohydrate and fat oxidation:

subse-The general formula for the calculation of energy production (E) derived from these figures is:

Oxygen consumption = 0 829 C + 0 967 P + 2 019 F

Carbon dioxide production = 0 829 C + 0 885 P + 1 427 F

Energy production = 17 5 C + 18 1 P + 39 6 F

C = −2 97 oxygen consumption + 4 17 carbon dioxide production − 0 39 P

F = 1 72 oxygen consumption − 1 72 carbon dioxide production − 0 32 P

E = 16 20 oxygen consumption + 5 00 carbon dioxide production − 0 95 P

In  this  formula  the  contribution  of  P  to  E,  the  so-called  protein  correction,  is only small. In the case of a normal protein oxidation of 10–15 % of daily energy production, the protein correction for the calculation of E is about 1 %. Usually, only urine nitrogen is measured when information on the contribution of C, P, and 

F to energy production is required For calculating the energy production the tein correction is often neglected. Current techniques utilizing indirect calorimetry for the measurement of energy expenditure in man are: a ventilated hood, respira-tion chamber or the doubly labelled water method

pro-A  typical  example  of  a  ventilated-hood  system  is  an  open  canopy.  It  is  used 

to measure resting energy expenditure and energy expenditure for food ing or diet-induced energy expenditure The subject lies with his head enclosed

process-in a plastic canopy, sealed off by plastic straps around the neck (Fig. 2.2). Air is sucked through the canopy with a pump and blown into a mixing chamber where

a sample is taken for analysis. Measurements taken are those of the airflow and of the oxygen and carbon dioxide concentrations of the air flowing in and out. The most common device to measure the airflow is a dry gas meter comparable to that used to measure calor-gas consumption at home The oxygen and carbon dioxide concentrations are commonly measured with a paramagnetic oxygen analyser and

an  infrared  carbon  dioxide  analyser  respectively. The  airflow  is  adjusted  to  keep differences in oxygen and carbon dioxide concentrations between inlet and outlet within a range of 0.5–1.0 %. For adults this means airflow rates around 50 l/min. Measuring resting energy expenditure with a ventilated hood system implies that subjects are in rest Physical exercise of high intensity in the hours preceding the measurement has to be prevented and subjects are usually measured for 15–30 min after at least 15–30 min bed rest, i.e. the measurement lasts 30–60 min

Fig 2.2 Ventilated hood system

induced  energy  expenditure,  subjects  are  measured  at  least  12  h  after  their  last meal.  In  practice  this  means  measuring  resting  energy  expenditure  in  the  early morning after an overnight fast, ideally while subjects have stayed overnight in the laboratory to be sure they did not eat and had no vigorous exercise in the hours preceding  the  observation.  Measuring  diet-induced  energy  expenditure  requires measurements taken after the consumption of a (standardized) meal and keeping subjects in a supine position for many hours. Resting energy expenditure increases after the consumption of a meal and does not return to pre-meal levels until at least

In addition, to be able to measure only resting energy expenditure without diet-6 h afterwards

A respiration chamber is an airtight room, which is ventilated with fresh air Basically the difference between a respiration chamber and a ventilated hood sys-tem is size. In a respiration chamber the subject is fully enclosed instead of enclos-ing the head only, allowing physical activity depending on the size of the chamber With both methods, the airflow rate and the oxygen and carbon dioxide concen-tration difference between inlet- and outlet air are measured in the same way The  flow  rate  to  keep  differences  for  oxygen  and  carbon  dioxide  concentrations between  inlet-  and  outlet  air  in  the  range  of  0.5–1.0  %  is  slightly  higher  in  the respiration chamber than in the ventilated hood system as in the chamber subjects never lie down over the full length of an observation interval. In a sedentary adult 

a typical flow rate is 50–100 l/min, while in exercising subjects the flow has to be increased  to  over  100  l/min.  In  the  latter  situation  one  has  to  choose  a  compro-mise for the flow rate when measurements are to be continued over 24 h including active and inactive intervals. During exercise bouts the 1 % carbon dioxide level should not be surpassed for long periods. During resting bouts, like an overnight sleep, the level should not fall to far below the optimal measuring range of 0.5–1.0 %. Changing the flow rate during an observation interval reduces the accuracy 

of the measurements due to the response time of the system A normal size ration chamber has a volume of 10–30 m3 and is equipped with a bed, toilet, wash-basin and communication facilities like telephone, radio, television, and Internet. Basically  it  is  a  hotel  room  (Fig. 2.3). The  experimenter  sets  the  room  tempera-ture Food and drink is delivered through an air lock according to the experimental design Physical activity is often monitored with a radar system to know when and how often subjects are physically active A respiration chamber can be equipped with a cycle-ergometer or a treadmill to perform standardised work loads A res-piration chamber has a much longer response time than a ventilated hood Though the flow rate in both systems is comparable, the volume of a respiration chamber 

respi-is  more  than  20  times  the  volume  of  a  ventilated  hood.  Consequently,  the  mum length of an observation period in a respiration chamber is in the order of 5–10 h. The shortest observation is usually the measurement of sleeping metabolic rate (SMR). Subjects enter the chamber between 18.00 and 19.00 h, go to sleep at 23.00 h, and SMR is measured over the interval from 3.00 to 6.00 h, i.e. 8 h after closing the door of the chamber Then, oxygen and carbon dioxide concentration differences between inlet and outlet air are within the optimal measuring range of the analysers

mini-The doubly labelled water method is an innovative variant on indirect etry. The method was invented in 1955. It was not until 1982 before the method was first used in people The reason is that 18O-water is very expensive and you need to give a person a much bigger dose than you do a bird For the first years after the initial discovery it would have cost about $5000 to make a single meas-urement in an adult The isotope is not substantially cheaper now, but isotope ratio mass spectrometers have become so sensitive that the method can now work with much smaller doses of isotope Presently, the method is frequently used with peo-ple in several centres This method can be used to measure carbon dioxide produc-tion and hence energy production in free-living subjects for periods of some days

calorim-to several weeks. The optimal observation period is 1–3 biological half-lifes of the isotopes The biological half-life is a function of the level of the energy expendi-ture. The minimum observation duration is about 3 days in highly active subjects like participants of the Tour de France or premature infants with a very high energy turnover. The maximum interval is 30 days or about 4 weeks in elderly (sedentary) subjects An observation starts by collecting a baseline sample Then, a weighed isotope dose is administered, usually a mixture of 10 % 18O and 5 % 2H in water

Fig 2.3 Respiration chamber system

For  a  70  kg  adult,  between  100  and  150  cc  water  would  be  used.  Subsequently  the isotopes equilibrate with the body water and the initial sample is collected The equilibration time is dependent on body size and metabolic rate For an adult the equilibration  time  would  take  between  4  and  8  h.  During  equilibration  the  sub-ject usually does not consume any food or drink After collecting the initial sam-ple the subject performs routines according to the instructions of the experimenter Body water samples (blood, saliva or urine) are collected at regular intervals until the end of the observation period. Validation studies, comparing the method with respirometry, have shown that results based on the doubly labelled water method elicit an accuracy of 1–3 % and a precision of 2–8 %. The method requires high precision Isotope Ratio Mass Spectrometry, in order to utilize low amounts of the very expensive 18O isotope. There are different sampling protocols, i.e. multi-point versus two-point method. The Maastricht protocol implies a combination of both, taking two independent samples: at the start, the midpoint, and at the end of the observation period Thus an independent comparison can be made within one run, calculating carbon dioxide production from the first samples and the second sam-ples over the first half and the second half of the observation interval The doubly labelled water method gives precise and accurate information on carbon dioxide production.  Converting  carbon  dioxide  production  to  energy  expenditure  needs information on the energy equivalent of CO2, which can be calculated with addi-tional information on the substrate mixture being oxidised (Table 2.1). One option 

is the calculation of the energy equivalent from the macronutrient composition of the diet. In energy balance, substrate intake and substrate utilization are assumed to 

be identical Alternatively substrate utilization can be measured over a ative  interval  in  a  respiration  chamber.  In  conclusion,  doubly  labelled  water  pro-vides an excellent method to measure energy expenditure in unrestrained humans

represent-in their normal surroundings over a time period of 1–4 weeks

Comparing Indirect Calorimetry with Direct Calorimetry

With indirect calorimetry, the energy production is calculated from the oxygen consumption and carbon dioxide production The result is the total energy pro-duction of the body for heat production and work output With direct calorimetry, one measures heat loss only At rest, total energy expenditure is converted to heat During  physical  activity,  there  is  work  output  as  well. The  proportion  of  energy production for external work is the work efficiency

Here, an experiment is described on the assessment of man’s work efficiency

by simultaneous assessment of total energy expenditure with indirect calorimetry and  heat  loss  with  direct  calorimetry  (Webb  et  al.  1988).  Subjects  were  normal weight 20–25 years adults, five women and five men. The experiment started with 

an overnight stay for the measurement of resting energy expenditure, followed

by  a  6-h  exercise  session  (walking  on  a  treadmill  and  cycling  with  an  eter).  Gaseous  exchange  was  measured  in  a  respiration  chamber;  heat  loss  was 

ergom-measured with a suit calorimeter The suit calorimeter was a close fitting elastic undergarment, which carries a network of small plastic tubing over the entire body surface, except for the face, fingers and soles of the feet Water circulated through the tubing carries heat from the skin, which is measured as the product of mass flow of water and the change in temperature across the suit. Layers of insulating garments limit the exchange of heat with the environment The suit calorimeter was developed from a device needed to cool astronauts while they are active out-side their spacecraft Evaporative heat loss was known from insensible perspira-tion, i.e body weight change corrected for intake and output of solids and liquids, and for the mass difference between oxygen intake and carbon dioxide output.

At rest, energy production, measured with indirect calorimetry, matched heat loss, measured with direct calorimetry (Fig. 2.4). Resting energy expenditure was 

on average 100 Watt, typical for a young adult. During physical activity, heat loss was systematically lower than energy production The difference increased with walking  speed  and  cycling  load.  During  cycling,  energy  production  matched  the sum of heat loss and power output The work efficiency during cycling, power out-put divided by energy production, was in the range of 15–25 %

iture  with  indirect  calorimetry.  Direct  calorimetry  measures  heat  loss  only.  Heat loss matches total energy expenditure at rest but can be up to 25 % lower than total energy expenditure during endurance exercise

In conclusion, at present the state of the art is assessing total energy expend-Components of Expenditure

Daily  energy  expenditure  consists  of  four  components,  the  sleeping  metabolic rate (SMR), the energy cost of arousal, the energy cost of food processing or diet 

Fig 2.4 Energy production (left bar open) and heat loss (right bar stippled), as measured at rest 

and during walking and cycling When power output during cycling is added to heat loss, the sum

matches energy production (After Webb et al. 1988)

induced energy expenditure (DEE), and the energy cost of physical activity (AEE). Sometimes daily energy expenditure is divided into three components, taking sleeping metabolic rate and the energy cost of arousal together as energy expend-iture  for  maintenance  or  basal  metabolic  rate  (BMR).  BMR  is  usually  the  main component  of  average  daily  metabolic  rate  (ADMR).  The  analysis  of  determi-nants of energy expenditure and its components will be illustrated with data from

a study that examined the effects of diet composition on energy metabolism in 37 subjects, 17 women and 20 men, age 19–35 years. Subjects spent 36 h in a respi-ration  chamber,  followed  by  a  2-weeks  observation  of ADMR  in  daily  life  with doubly labelled water Body composition was assessed with deuterium dilution Figure 2.5 shows the average time pattern of energy expenditure and the compo-nents,  and  of  body  movement,  as  measured  over  the  24  h  cycle  in  a  respiration chamber in the 37 subjects

Sleeping  or  basal  metabolic  rate,  the  largest  component  of  ADMR  in  most subjects, is determined by body size Standardizing to an estimate of metabolic body size usually compares sleeping or basal metabolic rate against fat-free mass Fat-free body mass seems to be the best predictor Energy expenditure should not be divided by the absolute fat-free mass value as the relationship between energy expenditure and fat-free mass has a y and x intercept significantly dif-ferent  from  zero  (Fig. 2.6).  Comparing  SMR  per  kg  fat-free  mass  between women and men for the subjects as presented in Fig 2.6 results in a signifi-cant  difference:  0.143  ±  0.012  and  0.128  ±  0.080  MJ/kg  for  women  and  men, respectively  (p  <  0.0001).  The  smaller  the  fat-free  mass  the  higher  the  SMR/fat-free  mass  ratio  and  thus  the  SMR  per  kg  fat-free  mass  is  on  average  higher 

in women with on average a lower fat-free mass compared with men The cated way of comparing SMR or BMR data is by regression analysis. Covariates 

indi-Fig 2.5 Energy  expenditure  (upper line:  total  energy  expenditure;  centre line:  resting  energy 

expenditure) and physical activity (lower line) as measured over a 24-h interval in a respiration 

chamber Arrows denote meal times. Data are the average of 37 subjects (see text)

to be included are fat-free mass, fat mass, age and gender Then, gender does not come  out  as  a  significant  contributor  to  the  explained  variation.  In  our  group  of 

17 women and 20 men, the significant variables were fat-free mass and fat mass: SMR (MJ/d) = 1.39 + 0.93 fat-free mass (kg) + 0.039 fat mass (kg), r2 = 0.93. Apparently SMR was not different for women and men when corrected for indi-vidual differences in body composition. There remains a (theoretical) problem in this approach The covariates are significantly different for the two groups without much overlap as clearly shown in Fig 2.6  for  fat-free  mass.  Ideally  one  should compare SMR or BMR in a group of women and men with comparable body com-position However, then there will be other systematic differences The women have to be very muscular and lean, i.e endurance athletes, or the men have to be obese

Diet  induced  energy  expenditure  can  be  defined  as  the  increase  in  energy expenditure above basal fasting level divided by the energy content of the food ingested and is commonly expressed as a percentage The postprandial rise in energy expenditure lasts for several hours and is often regarded as completely terminated at approximately 10 h after the last meal. The experimental design of most studies on DEE is a measurement of resting energy expenditure before and after a test meal, with a ventilated hood system The observation is started after an overnight fast, where subjects must fast after the last meal at 20.00 h at the latest. Thus, with observations starting between 08.00 and 09.00 h the next morning, the fasting  interval  is  at  least  12  h.  Postprandial  measurements  are  made  for  several hours where subjects have to remain stationery, most often in a supine position, for the duration of the measurements. In some studies, measurements are 30 min in duration with 15 min intervals allowing i.e for sanitary activities The use of a res-piration chamber to measure DEE has the advantage of reproducing more physi-ological conditions over a longer period of time while regular meals are consumed

Fig 2.6 Sleeping metabolic

rate plotted as a function

of fat-free mass with the

calculated linear regression

line (women, closed dots; 

men, open dots)

ity of spontaneous activity and basal metabolic rate (Fig. 2.7). The level of resting metabolic rate after waking up in the morning, and directly before the first meal, was defined as basal metabolic rate. Resting metabolic rate did not return to basal metabolic  rate  before  lunch  at  4  h  after  breakfast,  or  before  dinner  at  5  h  after lunch. Overnight, basal metabolic rate was reached at 8 h after dinner consump-tion Theoretically, based on the amount of ATP required for the initial steps of metabolism and storage, the DEE is different for each nutrient. Reported DEE val-ues  for  separate  nutrients  are  0–3  %  for  fat,  5–10  %  for  carbohydrate,  20–30  % for  protein,  and  10–30  %  for  alcohol  (Tappy  1996). Thus,  the  main  determinant 

be evaluated as the difference in 24-h energy expenditure adjusted for the variabil-of DEE is the energy content of the food, followed by the protein fraction of the food.  In  healthy  subjects  with  a  mixed  diet,  DEE  represents  about  10  %  of  the total amount of energy ingested over 24 h

Activity induced energy expenditure is the most variable component of ADMR. The doubly labelled water method has provided truly quantitative estimates of AEE in daily life. Currently, however, there is no consensus on the way to normal-ize AEE for differences in body size A frequently used method to quantify physi-cal  activity  as  a  figure  without  dimension  is  by  expressing ADMR  as  a  multiple 

of BMR or SMR. It assumes that the variation in ADMR is due to body size and physical activity. The effect of body size on ADMR is corrected for by expressing ADMR as a multiple of BMR or SMR. However, the expression of ADMR as a multiple of BMR or SMR for comparison between subjects can be precluded by the fact that the nature of the relation between ADMR and BMR or SMR is highly variable between studies and often has a nonzero intercept. Alternatively, ADMR 

is corrected for the effect of body size in a linear regression analysis The results

of  the  37  subjects  show  no  difference  between  the  two  methods,  the  regression between ADMR  and  SMR  has  an  intercept  not  significantly  different  from  zero 

Fig 2.7 The pattern of

diet-induced energy expenditure

throughout the day Arrows

denote meal times

(Fig. 2.8). Additionally, many studies adjust AEE for differences in body size by expressing AEE per kg body mass, assuming that energy expenditure associated with physical activity is weight dependent. Differences between women and men were nearly removed by adjusting for body size by using ADMR/BMR. In conclu-sion, AEE is comparable for women and men when adjusted for body size and body composition by expressing ADMR as a multiple of BMR.

Assessment of Physical Activity

Physical activity is defined as body movement produced by skeletal muscles and resulting in energy expenditure There are a large number of techniques for the assessment of physical activity, which can be grouped into five general categories: behavioural  observation,  questionnaires  (including  diaries,  recall  questionnaires and  interviews),  physiological  markers  like  heart  rate,  calorimetry,  and  motion sensors. Validated  techniques  of  estimating  habitual  physical  activity  are  needed 

to study the relationship between physical activity and energy balance The est obstacle to validating field methods of assessing physical activity in humans has been the lack of an adequate “gold standard” to which techniques may be compared The interrelation of various field methods may be of some value, but because there are errors in all methods it is impossible to determine the true valid-ity of any one of them in doing so However, calorimetry, more specifically the doubly labelled water method, has become the gold standard for the validation of field methods of assessing physical activity Then, physical activity is validated against activity induced energy expenditure (AEE)

great-Motion  sensors  are  the  most  promising  for  the  assessment  of  physical  ity Sensors can be applied in free-living subjects over prolonged periods of time

activ-Fig 2.8 Average daily

metabolic rate plotted

as a function of sleeping

metabolic rate with the

calculated linear regression

line (women, closed dots; 

men, open dots)

When equipped with a data memory to store information on body movement, they can also be used to study patterns of physical activity in time. Various sen-sors have been developed from mechanical devices to electronic accelerometers Accelerometers can provide information about the total amount, the frequency, the intensity, and the duration of physical activity. Validation studies should be inter-preted with care The validity is generally based on a comparison between acceler-ometer output and doubly labelled water assessed energy expenditure in a multiple regression analysis with subject characteristics as additional covariates The sep-arate contribution of accelerometer counts to the explained variation in energy expenditure is often not presented (Plasqui and Westerterp 2007). Results as pre-sented in the following chapters are based on physical activity measurement with a tri-axial accelerometer for movement registration (Tracmor). The Tracmor was the first device to be validated in a published study that utilized double-labelled water (Bouten  et  al.  1996).  This  device  is  now  commercially  available  (Bonomi  et  al.  2010).

The method of choice for the assessment of physical activity is a function of several parameters The five methods described above were ranked on six param-eters including subject interference, subject effort, providing information on activ-ity context, providing information on activity structure, the objectivity of the data, and the time and cost involved in the application (Table 2.2). An example is the comparison of the daily time budget with the daily energy expenditure of a sub-ject with an activity factor, ADMR/BMR, of 1.75 (Fig. 2.9). In the time budget, 

75  %  of  time  is  devoted  to  activities  inducing  an  energy  expenditure  lower  than 1.75  times  BMR  like  sleeping,  lying  down,  sitting  and  standing  without  move-ment, and 25 % of time to activities inducing an energy expenditure higher than 1.75 times BMR like standing active i.e. washing dishes, walking, cycling and run-ning (Fig. 2.9a). For total energy expenditure, the energy associated with the lower and higher intensity activities has a nearly fifty–fifty distribution (Fig. 2.9b). For activity induced energy expenditure, energy associated with activity during sitting and standing is on average similar to energy expenditure associated with the more

Table 2.2 Ranking of methods for the assessment of habitual physical activity on six different 

parameters, where 1 denotes the highest and 5 the lowest rank (After Westerterp 2009)

Subject interference

Subject effort

Contextual 

information

Activity structure

Objective 

data

Observer  time/cost

dynamic activities like walking, cycling and running (Fig. 2.9c). Accelerometers, more specifically tri-axial accelerometers, are the only devices with sufficient sensitivity to detect the small movements during sitting and standing A new development is the use of accelerometer sensors to identify activity types with classification algorithms These methods are based on several accelerometers posi-tioned  on  different  body  parts:  chest,  legs,  and  feet;  to  identify  different  move-ments and postures. In a further development, identification of activity types has been investigated using one single acceleration sensor, placed on the waist or on the chest The ultimate single sensor with a sophisticated algorithm to track the type, duration and intensity will never fully cover all aspects due to the immense activity diversity However, a single sensor might be preferable over a multi-sensor system, interfering with the parameter to be assessed (Bonomi et al. 2009).

Fig 2.9

Daily time (a, % of time) and total energy (b, % of energy total expenditure), and activ-ity energy (c, % of activity induced energy expenditure), where daily physical activities are split 

in seven categories with increasing intensity, for a subject with an average activity factor (total  energy expenditure equals 1.75 times basal energy expenditure) (After Westerterp 2009)

Assessment of Food Intake

The measurement of habitual food consumption in man is one of the hardest tasks

in energy balance studies The two basic problems are the accurate tion of a subject’s customary food intake, and the conversion of this information

determina-to nutrient and energy intake Any technique used determina-to measure food intake should not be so intensely applied as to interfere with the subject’s dietary habits and thus alter the parameter being measured The next problem is for how long does food intake need to be measured before the information can be said to be a true reflection  of  habitual  food  intake,  i.e.  the  food  an  individual  normally  consumes 

to provide the energy and nutrient requirements for his regular everyday ties. Methods to measure food intake at the individual level include dietary record and dietary recall The food record method requires subjects to record types and amounts of all foods consumed over a given time interval The foods are weighed

activi-or recactivi-orded in household measures like cups and spoons The latter infactivi-ormation

is translated to weight or volume by measuring the actual ‘tools’ used or adopting standard  values  from  reference  tables.  Dietary  recalls  use  the  subjects’  report  of intake over the previous 24 h period (24 h-recall) or the report of customary intake over the previous week up to the past year(s) (diet history). Here, the same meth-ods are used to quantify the reported intake from information on self-determined portion sizes Bias in the assessment of dietary intake, mostly underreporting,

is illustrated with studies comparing reported intake with doubly labelled water assessed energy expenditure

Under  reporting  of  habitual  intake  can  be  explained  by  under  recording  and under  eating.  Comparing  reported  food  intake  and  water  intake  with  energy expenditure and water loss can separate the two errors Since most foodstuffs con-tain water, when subjects record food intake they are also recording water intake

In healthy individuals, water balance is preserved and is therefore an independent indicator for under recording The recording precision of water intake is assumed

to be representative for total food recording, as most foodstuffs contain water Under  eating  during  food-recording  was  monitored  by  measurement  of  body mass Body mass changes over a food recording period are compared with normal body  mass  fluctuations.  Figure 2.10 shows the percentage misreporting, divided into  mis-recording  and  a  change  in  diet  as  observed  in  lean  women  (Goris  and Westerterp 1999), obese men (Goris et al. 2000), elderly men and women (Goris 

et al. 2001), and depleted patients (Goris et al. 2003). Both the obese men and lean women ate less while recording food intake, but probably for different reasons The lean women ate less because weighing and recording food intake was per-ceived as a great burden, which might also count for the obese men However, the obese men used the recording period also as an opportunity to start dieting The recording error observed in the obese men and in the elderly men and women was probably due to under estimation of self-determined food portion sizes and to not recording  of  all  foods  consumed.  Only  the  depleted  patients  reported  their  food intake accurately and they did not change their diet while recording food intake

Misreporting  of  food  intake  has  many  consequences.  In  a  controlled  tion study on energy restriction and body composition in man in the higher body weight range, the design was to start with a weight maintaining run-in period of

interven-2 weeks where energy expenditure was measured as well. During the run-in period subjects  received  a  weight-maintaining  diet  based  upon  the  outcome  of  a  7-day dietary  record.  Subsequent  energy  restriction  of  20  %  over  10  weeks  was  based 

on reported intake as well Subjects already lost some weight in the run-in period, and the weight loss of 0.75 kg/week over the subsequent 10 weeks was higher than expected. Reported intake appeared to be 82.5 % of doubly labelled water measured energy expenditure The underreporting resulted in an actual level of energy restric-tion of 33 % rather than 20 % (Velthuis-te Wierik et al. 1995). Secondly, underre-porting of food intake seems to be more of a concern for specific food items, which are generally considered ‘bad for health’ An example is the inverse relation between fat  intake  and  obesity  entitled:  “the  American  paradox”.  In  the  adult  population the prevalence of overweight has increased and at the same time reported energy intake and %energy from fat has decreased. This might be due to a lower physical activity and a higher consumption of low-energy foods but underreporting has also increased. Combining the results of studies showing selective underreporting of fat intake, the reported decrease in energy and fat intake seems to be doubtful National health campaigns aimed at lowering fat intake might not be so successful as it is concluded from the results of national food consumption measurements showing

a decline in reported fat intakes over several years Food supply data do not prove a clear reduction of dietary fat intake and there are indications for the opposite, giving

a potential explanation for the current obesity epidemic (Goris and Westerterp 2008)

Fig 2.10 Misreporting food intake in a range of subjects: lean women (dieticians); obese men; 

elderly  men  and  women;  and  depleted  patients.  Total  misreporting  is  calculated  as  measured 

energy expenditure minus reported energy intake divided by measured energy expenditure times

100 %, and divided in under-eating (stippled bar) and under-recording (open bar)

Assessment of Body Composition

Energy  from  food  (EI)  and  energy  expenditure  (EE)  together  result 

in  growth  (EG).  Growth  equals  energy  intake  minus  energy  expenditure: 

conse-quence of a discrepancy between energy intake and energy expenditure, i.e growth in terms of a change in the energy content of the body A further restriction

of this presentation is the age of the subjects under consideration Whereas growth

is usually seen as the development of infants from birth to maturity, this section mainly considers changes in weight and body composition in adult life, as a result

In vivo body composition can only be measured indirectly. There are nowadays 

a variety of methods with different assumptions and limitations All these tions stem from the chemical analysis of six adult cadavers, as performed in the end of the forties and the early fifties of last century, from subjects with a nor-mal body condition until death The general model for body composition is the two-compartment  model,  i.e.  the  discrimination  between  fat  mass  (FM)  and  fat-free mass (FFM). FM is assumed to be triglyceride without water; with a density 

assump-of 0.90 g/cc. FFM is assumed to have a water content of 73 % and a density of 1.10 g/cc. There are two generally accepted indirect methods for the measurement 

of body composition based on one or more of the assumptions mentioned above: densitometry and isotope dilution. Densitometry includes a measurement of body weight and body volume The technique for the assessment of body volume is hydro densitometry or air displacement plethysmography. Isotope dilution for the measurement of total body water is generally performed with deuterium, the stable isotope of hydrogen Newer techniques for the measurement of body composition are all double indirect, validated against indirect methods, and therefore based on more assumptions. One commonly used new technique to estimate body composi-tion is from electrical conductance of the body The conductivity of the body is supposed to be a reflection of FFM, as FFM contains virtually all water and con-ducting  electrolytes  in  the  body.  Corrections  are  necessary  for  conductor  length and  other  dimensions.  Results  have  been  validated  with  simultaneous  total  body 

water  measurements  using  isotope  dilution.  Results  are  a  function  of  the  tions for calculation of body composition from body impedance for the population under study. Most laboratories use their own equations because of differences in equipment and methodology. Another common technique used to estimate FM is dual energy X-ray absorptiometry (DEXA). DEXA scans were originally designed for the measurement of mineral mass, currently DEXA scans have also been found useful for the estimation of FM. DEXA is nowadays a commonly used technique 

equa-in clequa-inical practice

Each method for the assessment of body composition has an uncertainty in the order  of  magnitude  of  minimally  1.5  kg  FM  and  FFM. A  combination  of  inde-pendent measurements can reduce this measurement bias. In a three-compartment model, based on the measurement of body mass, body volume and total body water, the claimed precision is 1.0 kg for FM and 0.7 kg for FFM. A further slight improvement is reached in a four compartment model for body composition, sub-dividing  FFM  in  total  body  water,  protein  mass  and  bone  or  mineral  mass.  The four compartment model nowadays is the ‘gold standard’ for body composition, measuring four variables: body mass, body volume and total body water with the 

‘traditional’ methods, and mineral mass with dual energy X-ray absorptiometry The precision will never reach the level of 0.001 kg for BM with integrating elec-tronic  balances.  On  the  other  hand  the  precision  of  an  average  household  bath-room scale for the measurement of BM usually is not better than 1.0 kg. Putting the scale in another corner of the room often results in a difference of 0.5–1.0 kg. Everybody is familiar with discrepancies of body weight measurements between different scales Thus the essential starting point of the measurement of body com-position and changes in body composition is an accurate measurement of BM. For comparative studies, subjects should be measured with minimal clothing, minimal gut contents (post-absorptive) and with an empty bladder

An easy to measure indicator for body fat mass is the body mass index (BMI). Variation in body weight, adjusted for height, is a measure for fat mass. Heavier subjects are generally fatter subjects Body mass is adjusted for height by divid-ing weight by height squared: BMI  = body mass/height2 (kg/m2). For adults, a normal value ranges between 18.5 and 25 kg/m2, 25–30 kg/m2 denotes overweight and  values  >30  kg/m2 indicate obesity Exceptions are power athletes having a higher  BMI  through  a  higher  muscle  mass. The  rowers  of  the  ‘Holland  eight’  at the  1996  Olympic  games  in Atlanta  had  a  typical  body  weight  of  100  kg  and  a height of 2 m, i.e. a BMI of 25 kg/m2. However, with 10 % body fat they certainly were not fat

Energy Balance and Macronutrient Balance

Disturbance of energy balance results in energy mobilization or energy storage in body reserves Energy intake is via consumption of the macronutrients, i.e car-bohydrate, protein, fat and alcohol At a positive energy balance, excess energy is