The Encyclopedia Of Nutrition And Good Health - O potx

Before then, peoplewere considered overweight if their weight was at least 10 percent to 20 percent over optimal body weight.. Obesity was defined as being morethan 25 percent over the o

468

oats (Avena sativa) A common cereal GRAIN

grown in temperate regions, particularly in North

America and northern Europe There are six

species, including common oats and cultivated red

oats, that are grown in the Americas Oats are

clas-sified as winter and spring varieties, according to

their planting time Only about 5 percent of the

U.S crop is used as a food crop; most ends up as

livestock feed An inedible, loose, pithy hull

sur-rounds the kernel, or groat, and must be removed

for human consumption

Pure oats and pure oat BRAN are the least

processed form of oats Oat flakes, prepared by

steaming and flaking whole kernels, are the basis

for porridge Oatmeal is prepared by cutting

ker-nels to small granules with a mealy texture

Con-sumption of old-fashioned oatmeal as a BREAKFAST

CEREALhas declined with the increased popularity

of ready-cooked oatmeal cereals Rolled oats,

pre-pared by crushing oats with still rollers, are used in

breakfast food, cookies, breads, and GRANOLA,

which is a mixture of rolled oats, honey, nuts,

raisins, or dates Milling produces oat flour Oat

flour contains a natural ANTIOXIDANTthat increases

the stability of oat flour in storage

Oat Bran

Oat bran is derived from an outer layer of oat

ker-nels by milling It is a good source of SILICON, a trace

mineral needed for healthy joints, and a form of

FIBER called beta-glucan The fiber in oat bran is

water soluble and differs from water-insoluble

WHEAT bran, the kind usually found in

bran-enriched breakfast cereals Eating oat bran daily in

muffins and a bowl of hot oatmeal—together with

daily exercise and eating less animal FATas found in

red MEAT and BUTTER—can lower blood fat and

CHOLESTEROLeven in diabetics Oat bran alone has

a modest effect in lowering elevated levels of theless desirable LOW-DENSITY LIPOPROTEIN(LDL) cho-lesterol Oat bran has been used as a fat substitute

to reduce fat in beef and pork sausage products Amixture of oatmeal and oat flour has been devel-oped by the USDA as a fat-substitute called Oatrim

or “hydrolyzed oat flour.” Oatrim contains onecalorie per gram, as compared with nine caloriesper gram of fat and four calories per gram ofSTARCH This fat substitute is used in baked goodsand processed meats, and other products are underdevelopment

Oatmeal

Hot oatmeal is a traditional breakfast, and its gence as an important source of fiber has caused aresurgence in popularity Steel cut, rolled, or quick-cooking oats all contain the same amount of fiber.However, processed, cold oat breakfast cereals con-tain much less fiber (about 2 g per serving) Dryoatmeal contains about 14 percent protein, butcooked oatmeal is only about 2 percent protein.Nutrient content of regular cooked oatmeal orrolled oats, (1 cup fortified) is: 145 calories; pro-tein, 6 g; carbohydrate, 25.2 g; fiber, 9.23 g; fat, 2.3g; iron, 1.6 mg; sodium, 285 mg; vitamin A, 453retinol equivalents; thiamin, 0.53 mg; riboflavin,0.29 mg; niacin, 5.9 mg

emer-obesity An excessive accumulation of body fatfor a given body size based on muscle and bone(frame size) In 1998 the federal governmentadopted new standards for determining whether aperson is overweight or obese Before then, peoplewere considered overweight if their weight was

at least 10 percent to 20 percent over optimal body weight Obesity was defined as being morethan 25 percent over the optimal body weight for

men and 30 percent over the optimal body weight

for women

Under the new standards, a person with a BODY

MASS INDEX(BMI) of 25 or more is considered

over-weight The BMI is determined by dividing a

per-son’s weight in kilograms by the square of his or her

height in meters A healthy BMI falls between 19

and 25 A person with a BMI of 30 or above is

con-sidered obese According to statistics compiled by

the World Health Organization, obesity is increasing

worldwide—an estimated 1.2 billion people in the

world are overweight Its rapid increase among

Americans during the 1990s (12 percent in 1991 to

17.9 percent in 1998) prompted some health

offi-cials to conclude that it had reached epidemic

pro-portions In 2001 27 percent of adults between the

ages of 20 and 74 were obese The rate of

over-weight among children was 13 percent

Based on these figures, a former U.S surgeon

general, David Satcher, concluded that overweight

and obesity may soon cause as much preventable

disease and death as cigarette smoking The

condi-tions were already responsible for as many as

300,000 premature deaths each year, costing the

nation an estimated $117 billion The prevalence

varies among groups The average American adult

gains a pound a year through middle age

Childhood obesity has increased dramatically

since 1965 in the United States, reflecting an

increased prevalence of obesity among children in

Western countries The rising rate of overweight

and obesity among young people is of special

con-cern because childhood and adolescence is often a

time in life when people are the most active and

therefore least likely to gain excessive weight

Also, unhealthy nutrition and lifestyle habits that

lead to overweight and obesity developed during

this time have a good chance of continuing into

adulthood

The number of obese Americans has increased,

despite a national preoccupation with dieting The

fear of being fat has become an American

obses-sion U.S society places a premium on being

slen-der and most women and some men have dieted at

least once Being obese or overweight often brings

a profound social stigma affecting personal life, life

insurance premiums, and employment

opportuni-ties Nevertheless, in the 1980s the renewed

inter-est in healthy lifinter-estyles in America apparentlyaffected a limited number of people Sedentarylifestyles continue to prevail

Types of Obesity

Hyperblastic obesity is characterized by an sive number of fat cells Increased fat cell size isclassified as hypertrophic obesity, and individualswith hyperblastic-hypertrophic obesity haveincreased numbers of enlarged fat cells in their adi-pose tissue Hyperblastic obesity is usually associ-ated with childhood, while hypertrophic obesitydevelops later in life and is associated with diabetesand other aspects of metabolic imbalance

exces-Obesity as a Health Hazard

It has been noted that the death rate increases 2percent for each pound over a person’s healthyweight For persons who are 40 pounds over-weight, the death rate is estimated to be 80 percenthigher during the next 25 years of their life Leanmen survive longer than overweight men in theUnited States Obesity increases the risk of HEARTDISEASE, diabetes, GOUT, ARTHRITIS, CANCER of theliver and esophagus, GALLSTONES, hernia, intestinalblockage, kidney disease, and TOXEMIA of preg-nancy In the United States, obesity increases therisk of angina, high blood pressure (HYPERTENSION),high blood fat, elevated (LOW-DENSITY LIPOPROTEIN)LDL, and sudden death from heart disease Oneclue to understanding the relationship betweenobesity and elevated blood fat is the observationthat obese people have higher insulin levels, whichseems to promote higher blood lipids

The location of fat accumulation makes a ence in health risks Male-patterned obesity, withfat deposited primarily in the abdomen and trunk,

differ-is called android obesity (the “spare tire” or “apple”profile) Android obesity in men or women is asso-ciated with an increased risk for CARDIOVASCULARDISEASE, hypertension, elevated BLOOD SUGAR, andgallstones The greater the proportion of abdominalfat, the greater the risk Abdominal fat may bemore readily converted to cholesterol than fatdeposited elsewhere Pear-shaped people, with fataccumulation around the hips, do not experience

as much diabetes or high blood pressure or as manyheart attacks as those whose fat is around the middle

obesity 469

Possible Mechanisms

for Regulating Body Weight

Complex mechanisms involving the NERVOUS

SYS-TEM, the ENDOCRINE SYSTEM, and the DIGESTIVE

SYS-TEM, and adipose tissue regulate eating, energy

balance, and thus obesity Regions of the brain, such

as the HYPOTHALAMUSand the brain stem, help

reg-ulate food intake, body weight, body size, and body

fat content The hypothalamus plays a critical role in

eating and balancing energy requirements with

intake The lateral hypothalamus controls eating

activity; the paraventricular nucleus regulates

nutri-ent balance and the vnutri-entromedial hypothalamus

regulates energy balance by regulating the

sympa-thetic nervous system, which helps the body adapt

to stress The hypothalamus regulates the ENDOCRINE

SYSTEM(hormone secreting system) It activates the

PITUITARY GLAND, which signals the adrenal gland to

release GLUCOCORTICOIDS In turn, these STEROID

hor-mones regulate the nervous system, appetite, and

fat metabolism Obesity is linked to altered function

of the brain stem and hypothalamus and to changes

in the autonomic nervous system, which regulates

energy expenditure and regulates thermogenesis At

the molecular level, altered production of

NEURO-TRANSMITTERS, chemicals required to transmit nerve

impulses, brain peptides, and brain hormones, may

alter critical control and feedback mechanisms that

maintain body weight

Several hypotheses link food intake and energy

balance to regulate body weight through an

inter-play between the endocrine system and the

ner-vous system A hypothetical very general control

system involves the following components: A

pro-posed “controller” resides in the brain Signals

leav-ing the brain regulate heat production, physical

activity, food intake, energy storage as fat, and

metabolism for doing work and producing heat

These factors stimulate the release of hormones

Nutrients and hormones from various glands and

fat cells are then carried back to brain centers that

in turn generate signals that are interpreted by the

hypothalamus to diminish eating Stomach

disten-sion triggers the nervous system to create a feeling

of fullness The action of GLUCOSE (blood sugar),

fat, and protein in the intestines on receptors could

also send signals back to the brain to diminish

eat-ing behavior

In 2002 researchers reported that the recentlydiscovered “hunger hormone” ghrelin might be asignificant factor in determining why some peoplebecome obese and why most people find it hard tokeep weight off once it is lost A study of a smallgroup of obese people revealed they had muchhigher blood levels of ghrelin, which is produced

by stomach cells, after they lost weight throughdiet control and exercise In contrast, people wholost weight after gastric bypass surgery, whichreroutes the flow of food, had low levels of ghrelin.The extremely low levels of ghrelin in people whohad undergone gastric bypass surgery mightexplain why these people were usually more suc-cessful in keeping weight off Researchers cau-tioned that the results were preliminary and thatghrelin is probably only one of many tools the bodyuses to regulate body weight

Another hypothesis predicts a “set point” thattends to keep body weight at a constant level.According to the “set point” hypothesis for bodyweight, each person has a biologically determinedbody weight, believed to be inherited In someobese individuals, the set point may be too high.When fat cells decrease in size (for example, afterDIETING) they could indirectly signal the brain toincrease food consumption Thus, an obese personwith large numbers of fat cells could crave food,leading to excessive eating after dieting According

to a related hypothesis, some obese people earlier

in their lives, perhaps during early childhood, atemuch more than their bodies needed during theirformative years According to this proposal, thisevent patterned the body for burning energy andstoring fat Once overweight, obesity in these indi-viduals could be sustained even when consuming

an average amount of food

Insulin insensitivity (resistance to the action ofinsulin) correlates with obesity; increasing tissuesensitivity to insulin is hypothesized to lower thebody’s set point Recent discoveries shed light onthe relationships among obesity, satiety, and non-insulin dependent diabetes Fat cells normallysecrete a protein called LEPTINthat induces satiety.Leptin signals the brain to reduce consumption offatty foods and possibly to increase the basalmetabolism of fat cells Therefore, leptin helps reg-ulate body weight by limiting body fat accumula-

470 obesity

tion Mice with mutations on the gene coding for

leptin become obese Researchers now believe

obese people often make more than enough leptin,

but the brain does not respond effectively to shut

down eating because its binding sites or cell

signal-ing mechanisms are defective A region of the brain

likely to be affected by leptin is the HYPOTHALAMUS,

which integrates many functions of the body

Specifically, the region known as ventromedial

nucleus, which regulates satiety, may be involved

Leptin could shut off signals in the brain that direct

feeding (hunger signals), including neuropeptides

One possibility is neuropeptide Y, which induces

lab animals to eat more carbohydrate and fat In

the set point model, leptin could act like a

ther-mometer: When the body gets too thin, less leptin

is made, more food is eaten, and less energy is

con-sumed When the body gets too fat, more leptin is

made, less food is consumed, and more energy is

burned

A variety of mutations in other genes link

obe-sity and diabetes As an example, mutations in a

protein called beta3-adrenergic receptor, an

attach-ment site which binds a NEUROTRANSMITTER

(norep-inephrine), increase the risk of middle-age weight

gain and diabetes Under normal conditions

norep-inephrine produced by the sympathetic nervous

system stimulates fat cells to burn stored fats The

implication is that with a faulty neurotransmitter

attachment site in fat tissue, the body burns less fat

efficiently and calories accumulate As an

alterna-tive to the set point hypothesis, the “settling point”

theory proposes that body weight is not fixed, but

that it is maintained according to feedback loops

that are determined by an interplay between genes

and environment Systems controlling hunger and

satiety respond rapidly to dietary protein and

car-bohydrate, but the feedback from a fatty meal may

be too slow to prevent overconsumption Thus,

increased dietary fat could alter the body’s

equilib-rium and shift body fat upward The number of fat

cells in the body is a determining factor Fat cells

are added during childhood and it could very well

be that how much fatty food is consumed and how

many calories are burned before adulthood has a

major impact for the risk of obesity

Human obesity is a complex phenomenon with

many causes Inheritance as well as diet and

med-ical history can contribute to excessive weight gainand many questions about the detailed interrela-tionships remain unanswered Apparently, manygenes interact to control weight, it is thereforeunlikely that any single pharmacologic agentrelated to a gene product will substitute for chang-ing the diet and exercising regularly to maintaindesired weight In any event, very extensive clini-cal experience suggests that diets—that improveinsulin sensitivity and glucose tolerance by empha-sizing VEGETABLES and LEGUMES and minimizingsugary or high fat foods—together with regularphysical exercise can support long-term weight lossand reduce the risk of cardiovascular disease

Causes of Obesity

Many adults achieve an energy balance in whichcaloric intake matches energy expenditure Bodyfat does not change very much under these condi-tions Excessive body fat could be related to eatingmore calories or to small energy expenditure, orboth Energy expenditure refers to the caloriesspent for body functions, physical activity, diges-tion, and food metabolism Both heredity and theenvironment play a part in obesity and, therefore,there is no single approach to treatment Overeat-ing, differences in metabolism, AGING, genetic pre-disposition, and excessive food consumptionduring early childhood have been implicated

Overeating Clearly the prolonged tion of excessive calories, when energy intakeexceeds energy expenditure, leads to obesity.Energy expenditure refers to the calories spent forbody functions, physical activity, digestion, andfood metabolism Body fat can be reduced onlywhen energy expenditure exceeds caloric intake.The body adapts to excessive food consumption—whether excessive PROTEIN, CARBOHYDRATE, fat, or ALCOHOL—by storing the surplus calories as bodyfat Many reports have suggested that obese peopleeat the same, or sometimes less than nonobesepeople Using new research methods based oningesting double-labeled water, that is, water con-taining a “heavy” form of oxygen (O18) and

consump-“heavy” hydrogen (deuterium), investigators havedemonstrated that, on the average, obese peoplegenerally eat more, but they habitually underre-port their food consumption

obesity 471

Differences in Energy Expenditure Although

obese people are generally less active than

non-obese people, they tend to use the same amounts of

energy because they weigh more Sedentary

lifestyles contribute to obesity About 70 percent of

adult Americans fail to exercise 20 minutes or

more three times a week as recommended Most

people will lose weight if such an exercise program

is coupled with consuming no more than 1,500

calories daily Individuals who exercise regularly,

or who exercise before and after a

high-calorie meal, lose more energy as heat after eating

than those who do not exercise

Differences in Metabolism This picture is

unclear Very rarely do glandular imbalances lead

to obesity Cushing’s syndrome, excessive

produc-tion of glucocorticoids, a form of adrenal hormone,

is an example of hormone imbalance that can

pro-mote obesity Obese people do not have unusually

slow metabolisms When resting metabolic rates

are compared based upon the muscle/bone mass,

there is not a significant difference between

meta-bolic rates of nonobese and obese individuals

For-merly obese individuals preferentially store fat

rather than burn it, and studies suggest that

over-weight and obese people tend to eat more fat and

less carbohydrate In general, the body consumes

calories more slowly after weight is lost, and it

burns calories more rapidly when weight is gained,

for fat as well as for thin people One hypothesis

contends that people adjust their metabolism to

maintain a “set point” weight Thus someone who

has lost significant amounts of fat (10 percent of

their body weight) will burn fewer calories when

exercising than someone who has maintained his

or her weight without a weight-loss program

Apparently, the body adjusts its metabolism by

altering the efficiency of muscles in burning

calo-ries Recently, a type of prostaglandin has been

shown to act as a hormone to trigger the

produc-tion of fat cells from immature cells

Aging In the United States, both men and

women tend to become fatter with increasing age

This could be due to a decreased metabolic rate (a

lower BASAL METABOLIC RATE) and a sedentary

lifestyle coupled with an easy access to high-calorie

food

Meal Frequency The frequency of meals and

meal composition may be a factor in obesity Eating

fewer meals may increase fat deposition, whilesmaller, more frequent meals, with more food atbreakfast and less at supper, may promote weightloss

TV Watching Excessive TV watching correlateswith overeating Reduced physical activity, loweredmetabolic rates, as well as visual cues to eatinghigh-fat snack foods and drinking alcoholic bever-ages, contribute to the increased prevalence ofoverweight Dietary fat, which provides nine calo-ries per gram, is more fattening than either protein

or carbohydrate, which provide four calories pergram Fat calories in food differ from calories incarbohydrate: Fat in food is more easily converted

to body fat than is carbohydrate

Inheritance One broad generalization can bemade: Obesity persists over a life span Fat childrentend to become fat adults, suggesting a predisposi-tion to being overweight Early adulthood is animportant period for the development of lifelongpatterns The question remains, to what degree isobesity the product of genetics? Studies with twinssuggest that between 50 percent and 70 percent ofthe variability in relative body weight representsgenetic variability Current research focuses onlocating specific obesity genes Genes influenceboth metabolism and behavior Many genes regu-late hunger and satiety A flurry of recent research

has yielded impartial genetic discoveries: gene OB

causes fat cells to produce a satiety protein calledlepin A gene then codes for the receptor of thishormone in the brain Still another gene codes for

a hormone-producing enzyme (carboxypeptidaseE) A gene that codes for a neurotransmitter recep-tor (binding site; Beta3-adrenergic receptor) fornorepinephrine is also implicated in maintainingweight Mutations of these genes can increase therisk of obesity and diabetes in lab animals and pos-sibly in people There will be more to add to thisunfinished story as more discoveries are made

Successful Weight Loss

A Willingness to Change Therapeutic proaches to obesity and weight management havemet with only modest success Only 2 percent to 10percent of Americans who diet to lose weight andparticipate in weight loss programs will keep thepounds off more than several years Most of the lostfat is regained within a few months after the dieter

ap-472 obesity

discontinues the diet regimen Dieting without a

long-term commitment to changing daily habits is

destined to fail

Attitude is perhaps the most prominent factor in

changing behavior Regarding overeating,

under-standing underlying feelings for which overeating

compensates seems essential for permanent weight

loss Eating can provide immediate gratification, but

this seldom resolves deep-seated emotional issues

After short-term sensory satisfaction, emotional

pain or longing often returns For example,

responding to feelings of low self-esteem by crash

dieting does not solve the underlying issue, and too

often the dieter returns to old eating habits

Coun-selors recommend beginning with an inventory of

talents and qualities that fill your life with the most

satisfaction and choosing activities and relationships

that bring satisfaction and a sense of well-being

Slow Weight Loss Successful long-term weight

control requires the slow loss of body fat without

cyclic, on-again, off-again dieting (YO-YO DIETING)

Losing a pound a week helps maintain muscle

(LEAN BODY MASS) while preferentially losing fat

Exercise Exercising for life helps keep the body

engine “revved up,” so that more calories are

burned by muscle and less insulin is required to

dispose of elevated blood sugar following meals

Improved Diet A high-fat, high-calorie,

low-fiber diet is thought to be the major dietary factor

in obesity in the United States Therefore the

rec-ommended diet might be low in fat, high in fiber

and complex carbohydrates (60 percent to 70

per-cent of calories), with adequate protein (10 perper-cent

to 15 percent of calories) Emphasis on natural,

whole foods simplifies this task of avoiding the

per-vasive high-calorie foods that fill the American

food landscape Another approach to obesity and

overweight focuses on helping people through

advocacy and social support with the premise that

being overweight can be part of an enjoyable,

ful-filling life: The Association for the Health

Enhance-ment of Large People and the National Association

to Advance Fat Acceptance are two such groups

Weight Loss Drugs

Like diets, anti-obesity drugs tend to be effective

only as long as the patient follows the prescription

When drugs are withdrawn, weight lost usually

returns unless permanent behavior changes have

been made Amphetamines have adverse sideeffects: They have the potential for addiction andtolerance (more drug is required to get the sameeffect with chronic use) Another class of drug pro-motes nutrient malabsorption so that patients tak-ing these drugs do not absorb calories efficiently.Two appetite suppressants, fenfluramine anddexfenfluramine, were taken off the market by theU.S FDAin 1997 when it was discovered that thou-sands of patients who took these drugs developedpotentially deadly primary pulmonary hyperten-sion and heart valve abnormalities Dexfenflu-ramine was shown to cause these injuries whentaken alone, and fenfluramine was linked to valveproblems in patients who combined it with thedrug phentermine in a mixture popularly known

as “fen-phen.” Both fenfluramine and ramine helped patients lose weight by increasingserotonin levels in the blood stream, which pro-vided a sense of well-being and satiety The prob-lem, researchers discovered after the drugs wereremoved from the market, was that the drugsdestroyed the body’s ability to control the amount

dexfenflu-of serotonin circulating in the blood Excessiveamounts of serotonin can cause cell damage to car-diopulmonary structures

In late 2000 the FDA issued a public health sory warning patients about phenylpropanolaminehydrochloride (PPA) This drug is widely used inboth over-the-counter and prescription-only nasaldecongestants and for weight control in some over-the-counter drug products The warning was issuedafter medical researchers published a study show-ing that phenylpropanolamine increases the risk ofhemorrhagic stroke (bleeding into the brain or intotissue surrounding the brain) in women Men mayalso be at risk Since then the FDA has taken steps

advi-to remove PPA from all drug products No drug isboth entirely safe and effective for weight loss, nor

is it certain that taking current medications formany years is better than being fat Drugs that sup-press appetite are not recommended for those whowish to lose only 5 to 10 pounds of fat

Childhood Obesity

An estimated 13 percent of U.S children six to 11years old and 14 percent of adolescents 12 to 19years old are overweight The number of obesechildren and adolescents in the United States dou-

obesity 473

bled between 1982 and 2002 Obesity is recognized

as a U.S epidemic affecting children Low-income

minority children face even higher rates of obesity

An overweight adolescent between age 10 and 14

who has at least one overweight or obese parent

has a 79 percent likelihood of being overweight as

an adult

Childhood obesity is linked to many of the

fac-tors that cause adult obesity:

Heredity As in adult obesity, genes play a role

Children born to obese mothers are more likely to

be obese If both parents are obese, the probability

of their children becoming obese is very high

Overfeeding Some babies have more fat cells

than usual If they are also overfed, they are more

likely to become obese children In addition,

over-feeding a child may lead to larger, not more, fat

cells This may make controlling weight more

diffi-cult as an adult (It should be pointed out that

plump babies do not necessarily become obese

adults.)

Lower Metabolism Infants who become

over-weight during their first year have a lower basal

metabolic rate than usual Their mechanism for

reg-ulating body weight might be lower than average

Eating Too Much Fatty Food The more JUNK

FOODis consumed, the more likely the child will be

obese Bogalusa Heart Study is an ongoing

popula-tion study to examine risk factors for

cardiovascu-lar disease in children Results from this study

reveal that children who consume more than 30

percent of their calories from fat were more likely

to eat less CALCIUM, IRON, MAGNESIUM, and vitamins

like RIBOFLAVIN, NIACIN, THIAMIN, VITAMIN B6,

VITA-MIN B12, and VITAMIN E

Too Much TV and Not Enough Exercise The

odds of becoming obese increase with the number

of hours of TV viewed each day Children’s basal

metabolic rate decreases, and they get less physical

activity Children who watch TV eat more of the

high-calorie, highly processed food they see

adver-tised, and parents fill the role of food “gate keepers.”

Children eat what is available to them, whether it is

candy, soft drinks, or fatty convenience foods, or

fruit, low-fat foods, and sugar-free beverages

The home environment and parents present the

model for a child’s eating habits A child’s shift to a

more healthful lifestyle needs to be nurtured by

parents to become permanent As with overweight

adults, regular exercise is extremely important inchildren’s health and maintaining a desirableweight

However, overzealous dietary restrictions byparents can encourage self-imposed dieting andeating disorders, a prevalent problem among chil-dren and adolescents in the United States As many

as 80 percent of 10-year-old girls suffer from a fear

of body fat; some already show signs of dieting,bingeing, overeating, and anorexia The messagethey are receiving is that any accumulation of bodyfat is socially unacceptable However, amongwhite, middle-class, healthy girls in the UnitedStates, weight before and during puberty does notseem to be a predictor of weight gain at middle age

On the other hand, weight gained after puberty(during early adolescence) has correlated withweight gain as adults For boys, prepuberty weightappears to be a good predictor of adult obesity Aphysician should be consulted before talking tochildren about weight Periodic increases in fat,especially among girls, are a normal occurrence.Weight maintenance, after the child has grown intohis or her own weight, is preferable to dieting.Generally, children can be taught to prefer lowerfat foods by exposure and availability (See alsoMALNUTRITION; WEIGHT MANAGEMENT.)

Asayama, Kohtaro et al “Increased Serum Cholesterol

Ester Transfer Protein in Obese Children,” Obesity

Research 10 (2002): 439–446.

Cummings, D E et al “Plasma Ghrelin Levels After

Diet-Induced Weight Loss or Gastric Bypass Surgery,” New

England Journal of Medicine 346, no 21 (May 23,

2002): 1,623–1,630.

octacosanol A complex alcohol that is a normalconstituent of wheat germ and wheat germ oil.Other sources include whole grain cereals, seedsand NUTS, and many plant oils and WAXES Persis-tent claims that octacosanol supplementation has apositive effect on physical endurance and muscularstrength have not been substantiated by research.The Federal Trade Commission concluded thatwheat germ oil did not improve endurance or sta-mina Octacosanol seems to improve reaction time.(See also ERGOGENIC SUPPLEMENTS.)

oil See VEGETABLE OIL

474 octacosanol

oil palm (Elaeis guineensis) A palm that is a

major source of edible oil The oil palm yields more

oil per acre than any other plant It originated in

West Africa, and plantations now exist in Malaysia,

China, and Indonesia, as well as Tanzania, the

Ivory Coast, Nigeria, and other regions Palm oil is

prepared from fibrous pulp of the fruit, and palm

kernel oil is obtained from the seed or kernel,

which contains about 50 percent oil Palm kernel

oil is used for margarine production and food

man-ufacture It is among the most SATURATED FATS,

con-taining 86.7 percent saturated FATTY ACIDS, 1.6

percent polyunsaturated fatty acids, and 11.7

per-cent monounsaturated fatty acids (See also

COCONUT OIL; TROPICAL OILS.)

okra (Hibiscus esculentus; Abelmoschus

esculen-tus) A vegetable that bears seeds in edible pods

whose ancestors may have been widely distributed

from Africa to India Okra now grows in regions

with a moderate climate, including the southern

states of the United States Much of the U.S okra

crop is frozen or canned Okra contains a mucilage

that acts as a thickener in soups and stews Because

okra changes to an unappetizing color when

cooked in utensils containing iron, copper, or brass,

glass or stainless steel containers are used Okra’s

slippery mucilage is balanced by acidic foods like

tomatoes and lemons and by vinegar Okra, long

considered part of Deep South cuisine, is also part

of Indian, Caribbean, South American, and African

recipes

Nutrient content of okra (8 pods, 85 g, cooked)

is: 27 calories; protein, 1.6 g; carbohydrate, 6.1 g;

fiber, 2.75 g; calcium, 54 g; iron, 0.38 mg;

potas-sium, 274 mg; vitamin C, 14 mg; thiamin, 0.11 mg;

riboflavin, 0.05 mg; niacin, 0.74 mg

oleic acid A nonessential FATTY ACIDand a

com-mon constituent of FATS and OILS found in foods

and fat synthesized by the body Oleic acid is

dis-tinguished from the other common fatty acids, the

energy-rich building blocks of fats and oils It

con-tains 18 carbon atoms and a single double bond, is

deficient in hydrogen atoms, and thus is classified

as a monounsaturated fatty acid In contrast,

satu-rated fatty acids are building blocks filled up with

hydrogen atoms and polyunsaturated fatty acids

possessing two or more double bonds and are moreunsaturated than oleic acid Oils rich in oleic acidare called monounsaturated oils VEGETABLE OILSlike olive oil, AVOCADOoil, and CANOLA OILcontainhigh amounts of oleic acid Oleic acid-rich veg-etable oils seem to lower the less desirable forms ofblood CHOLESTEROL, LOW-DENSITY LIPOPROTEIN(LDL)with high fat intake, and to increase more desirableforms of cholesterol, HIGH-DENSITY LIPOPROTEIN(HDL) Olive oil is more stable to oxidation thanpolyunsaturates such as safflower oil or corn oil.The recommendation is to decrease fat and oil con-sumption generally, and to use more monounsatu-rates in cooking, rather than saturates (butter, lard,shortening, coconut oil, or palm oil) or polyunsat-urates (such as CORN OIL, SAFFLOWER oil, and SOY-BEANoil)

Olestra (sucrose polyester, imitation fat [Olean])

A noncaloric fat substitute approved for use insnack foods such as crackers, potato chips, andother chips Olestra tastes like LARDand VEGETABLEOILS; it is neither digested nor absorbed by thebody By comparison, FATand oils contain 126 calo-ries per tablespoon Olestra resembles the structure

of fat, except that it has a molecule of sucrose at itscore to which are attached eight fatty acids, ratherthan three Because it possesses a new substance,sucrose polyester had to be approved by the U.S.FDA All products containing Olestra are labeled tonotify the consumer that Olestra may causeabdominal cramping and loose stools and that itinhibits the uptake of certain nutrients Vitamins A,

D, E, and K have been added The question of absorption of CAROTENOIDShas not been addressed

mal-In addition to these potential safety problems,animal studies suggest Olestra can cause liver dam-age, birth defects, and cancer More complete stud-ies are needed to establish its safety Regardless oftheir source, fat substitutes cannot replace the need

to eat less high-fat food and to change eatinghabits (See also WEIGHT MANAGEMENT.)

olive (Olea europaea) The oil-rich fruit of asemitropical evergreen adapted to hot, dry cli-mates Olives were probably first cultivated in theEastern Mediterranean region as early as 6000 B.C.There are now more than 60 varieties Mediterran-

olive 475

ean countries remain major producers; together,

Italy and Spain produce more than half of the

world’s olives and 60 percent of the world’s olive

oil production Olives are also grown in Australia,

China, Greece, Turkey, and France, as well as in the

United States Spanish colonists introduced olives

to California in the 18th century; that state

contin-ues to be a major domestic supplier At maturity,

ripened olives contain 15 percent to 35 percent oil,

and OLIVE OILis a major cooking oil The oil content

varies according to soil conditions, climate, and

time of harvest

Olives must be processed for consumption In

the Spanish method, green (unripe) olives are first

treated with alkali, then fermented, and canned or

bottled The alkali destroys a bitter constituent

called oleuropein In the American method,

half-ripe, reddish fruit are cured in lye (strong alkali)

Olives darken as pigments oxidize They are rinsed

and then placed in fermentation tanks containing

BRINE In the Greek method, fully mature olives are

harvested and soaked in brine to remove the bitter

components Ripe, pitted olives (10.47 g) provide

50 calories; protein, 0.4 g; carbohydrate, 2.9 g;

fiber, 1.4 g; fat, 4.5 g; calcium, 42 mg; iron, 1.5 mg;

sodium, 410 mg; and traces of B vitamins

olive leaf extract The extracted juice of the leaf of

the olive tree This substance has been used for

cen-turies as an herbal remedy for a variety of ailments,

especially infection and fever In the mid-1800s Dr

Daniel Hanbury reported that olive leaf extract was

effective in reducing fever associated with an

epi-demic of malaria on a Mediterranean island

In recent decades researchers have discovered

that eleuropein, an ingredient in olive leaf extract,

has antibacterial, antiviral, and anti-inflammatory

properties and may help reduce the risk of

CORO-NARY ARTERY DISEASE by lowering LOW-DENSITY

LIPOPROTEIN(LDL) CHOLESTEROL Laboratory studies

conducted in the 1960s revealed than an active

ingredient in eleuropein (elenolic acid) either

killed or inhibited the growth of a number of

path-ogenic organisms, including bacteria, yeasts, and

viruses, but because the compound rapidly binds to

proteins in the blood, rendering it ineffective,

attempts to develop a marketable drug from the

substance were abandoned

There is limited clinical evidence suggesting thatolive leaf may help lower high blood pressure.However, reliable clinical studies on human beingsthat confirm the safety and potential health bene-fits of olive leaf extract do not yet exist Neverthe-less, nonscientific literature is filled with anecdotalaccounts of the extract’s ability to heal It has beenavailable as a dietary supplement in the UnitedStates since the mid-1990s

Ruiz-Gutierrez, V et al “Oleuropein on Lipid and Fatty

Acid Composition of Rat Heart.” Nutrition Research 15,

no 1 (1995): 37–51.

olive oil An oil extracted from ground olives.Spain is currently the world’s leading producer ofbulk olive oil; Italy is a leading producer of bottledolive oil The International Oil Agreement wasnegotiated through the U.N to ensure olive culti-vation and olive oil production in the Mediter-ranean region

To produce olive oil, crushed olives are ically pressed several times The temperature forolive oil extraction can be 50° to 110° F There is nolegal definition of “cold-pressed” oil, but the hotterthe pressing, the more oil is extracted

mechan-Olive oil is classified as a monounsaturated fatbecause it contains large amounts of OLEIC ACID, amonounsaturated FATTY ACIDwith one double bondand lacking two hydrogen atoms—in contrast withpolyunsaturates, containing polyunsaturated fattyacids with two or more double bonds and lackingseveral pairs of hydrogen atoms, and saturates,containing predominantly saturated fatty acids (nodouble bonds and completely filled up with hydro-gen atoms) Because olive oil is more stable to oxi-dation and rancidity, olive oil is not chemicallystabilized (partially hydrogenated) Olive oil, likeall oils, provides 14 g of fat per tablespoon, equiva-lent to 120 calories

Proposed Grades of Oil

An independent U.S FDA analysis of 30 importedolive oils revealed that five were not olive oil and

18 were mislabeled as “extra virgin” oil

“Extra virgin olive oil” is prepared frommechanical pressing and is filtered without refin-ing “Virgin olive oil” is not highly refined and has

a golden color and a unique flavor and taste The

476 olive leaf extract

acid content is no more than 1 percent Virgin olive

oil is filtered after pressing and is unrefined; the oil

has a rather fruity flavor, and its acid content is less

than 2 percent Oil labeled “olive oil” is usually

listed as being “100 percent pure.” It is actually a

blend of refined and unrefined olive oil and

accounts for about 70 percent of U.S olive oil

con-sumption Refining involves extraction at high

temperatures and with solvents, neutralization of

acids, and bleaching

Potential Health Benefits of Olive Oil

People who eat predominantly olive oil have

lower blood fat and cholesterol and a reduced risk

of clogged arteries Olive oil seems to lower blood

levels of the less desirable form of CHOLESTEROL,

LOW-DENSITY LIPOPROTEIN (LDL), while raising the

level of HIGH-DENSITY LIPOPROTEIN(HDL), the more

desirable kind of cholesterol If the intake of

polyunsaturates increases substantially above 7

percent of daily calories, the current average,

polyunsaturated oils lower LDL (a desirable effect)

but also lower HDL (an undesirable effect) By

fol-lowing current dietary guidelines that call for

eat-ing less fat (less than 30 percent of total calories)

and less saturated fat (less than 10 percent of

calo-ries), people necessarily increase their

consump-tion of unsaturates Substituting monounsaturated

oils for saturates and polyunsaturated fats and oils

may be desirable while decreasing total fat

con-sumption because high concon-sumption of

polyunsat-urates is more likely to promote the oxidation of

LDL cholesterol, the less desirable form, thus

increasing the probability that oxidized LDL will be

taken up by blood vessels and create plaque in

arteries Furthermore, animal studies suggest

polyunsaturates can increase the risk of some

forms of cancer Cooking with olive oil instead of

polyunsaturated vegetable oils (safflower oil, corn

oil, etc.) may be advantageous because olive oil

does not break down as readily when heated (See

also ATHEROSCLEROSIS; CARDIOVASCULAR DISEASE;

omega-6 fatty acids See ESSENTIAL FATTY ACIDS

onion (Allium cepa) A vegetable with an ground bulb closely related to GARLIC and leeks,belonging to the lily family Onions apparentlyoriginated in prehistoric central Asia, and weregrown in ancient Egypt, Greece, and Rome, as well

under-as China There are more than 500 varieties; all ofthe edible species possess a pungent bulb Euro-peans introduced onions to the Americas Today,China, the United States, and India produce thelargest yields, and onions rank sixth among veg-etable crops worldwide

Green onions may be harvested before the onionhas matured Alternatively, mature onion bulbs can

be harvested The length of time that dried bulbscan be stored ranges from several days to months,depending on the variety, their stage of maturity,and temperature and humidity during storage.There are two types of dry onion Flat onions,elongated Spanish onions, and Bermuda onionsare usually mild flavored They do not store as well

as globe or late-crop onions, which frequently sess a stronger flavor The latter store well and can

pos-be marketed throughout the year Onions can pos-becanned, dehydrated, frozen, or pickled

Onions and their relatives possess a complexfamily of sulfur compounds related to the sulfur-containing amino acid cysteine Once their layersare cut, the sulfur-containing compounds comeinto contact with an enzyme called allinase thatreleases volatile (gaseous) compounds that can irri-tate eyes Cooking onions and GARLIC modifiesthese sulfur compounds, and they are not so irri-tating after cooking

The medicinal properties of onions and garlichave been known for thousands of years, andrecorded use includes treatment of wounds andinfections, tumors, worms and parasites, weakness,FATIGUE, and asthma Onions resemble garlic interms of active ingredients and therapeutic effects.The consumption of garlic and onions correlateswith lowered blood cholesterol levels Generally,the higher the dose of garlic and onions, the greaterthe reduction Onions also seem to lower bloodCHOLESTEROL by helping to block cholesterol syn-thesis Onions and garlic contain a variety of pun-gent, sulfur-containing compounds One of these

onion 477

lowers BLOOD SUGAR; another counteracts blood

platelet stickiness and reduces the tendency for

blood to clot and, at the same time, raises

HIGH-DENSITY LIPOPROTEIN (HDL), the desirable form of

cholesterol that protects against cardiovascular

dis-ease Onions help decrease elevated blood sugar

levels in diabetics, possibly by slowing the

break-down of insulin, the hormone responsible for

stim-ulating sugar uptake from the blood They may also

increase insulin secretion

Onions as well as garlic contain compounds

that block the production of inflammatory agents

For example, onions contain a FLAVONOID called

QUERCETIN, a plant pigment known to reduce

INFLAMMATION.

Both onions and garlic have antibiotic properties

and have been shown to be effective against fungi

and parasites as well Furthermore, onions and

gar-lic contain substances that block tumor growth in

animals Sulfur compounds apparently induce

enzyme systems in the LIVER that detoxify

poten-tially harmful compounds Flavonoids are

ANTIOXI-DANTSthat block damage due to free radical attack

Free radicals are highly reactive molecules that

avidly attack cells Flavonoids play a role in the

anticancer properties of onions and garlic because

free radical damage is linked to cancer

Raw, chopped onions (1 cup, 160 g) provide 54

calories; protein, 1.9 g; carbohydrate, 11.7 g; fiber,

2.64 g; iron, 0.59 mg; potassium, 248 mg; vitamin

C, 13 mg; thiamin, 0.1 mg; riboflavin, 0.02 mg; and

niacin, 0.16 mg (See also CARCINOGEN; HEART

ATTACK.)

orange (Citrus sinensis) An orange-colored

CIT-RUS FRUIT, that is the most popular fruit crop in the

United States Orange trees grow in semi-tropical

regions and probably originated in Southeast Asia

and Southern China Spanish explorers and

colonists brought the orange to the New World in

the 16th century In the United States, oranges are

cultivated in Arizona, California, Texas, and

Florida

The three principal varieties of orange include

the sweet (common, China orange), C sinensis; the

loose-skinned orange, C mobilis; and the sour,

bit-ter Seville orange, C aurantium Sweet oranges are

represented by the blood orange, the navel orange

and the Valencia (Spanish) orange, in addition tothe Hamlin, Jaffa, and Pineapple varieties Onlysweet oranges are grown commercially in theUnited States

The color of the orange peel does not ily indicate maturity because most oranges arepicked green and exposed to ethylene gas at warmtemperatures to enhance the orange color Souroranges, such as the Seville, are grown in Spain formarmalade and orange liqueurs

necessar-Three quarters of U.S orange production isprocessed and 80 percent of this ends up as frozenorange juice concentrate Oranges and orange juicecontain large amounts of VITAMIN C, and this con-tributes a substantial percentage of the vitamin Cintake in the typical U.S diet The white inner por-tion of the peel is a good source of FLAVONOIDS,plant substances that act as antioxidants to preventoxidative damage

Certain individuals may be allergic to nents in the orange peel and neither the peel norproducts made from it should be eaten by suchpeople Citrus peel also contains citral, a compoundthat blocks the action of vitamin A Organic orangepeels have not been sprayed with pesticides Oneorange (131 g) provides 60 calories; protein, 1.2 g;carbohydrate, 15.4 g; fiber, 2.97 g; potassium, 237mg; vitamin C, 70 mg; thiamin 0.11 mg; riboflavin,0.05 mg; and niacin, 0.37 mg

compo-Orange Juice

Fifteen percent of the U.S orange crop is used forfresh orange juice Commercial orange juice maycontain up to 10 percent mandarin orange juiceand up to 5 percent sour orange juice Frozenorange juice concentrate contains up to four timeshigher concentrations of nutrients than fresh juice.Orange juice can be used to enhance the flavor ofroot vegetables and can be added to jams and mar-malades Orange juice is a good source of vitamin Cand POTASSIUM Most 100 percent orange juicesprovide 60 mg of vitamin C or more and 80 to 100calories per cup The current REFERENCE DAILYINTAKE(formerly the USRDA) for vitamin C is 60 mg.Vitamin C is readily oxidized upon exposure to theair to an inactive form Fresh-squeezed orangejuice loses 60 percent of its vitamin C when storedfor 24 hours at room temperature, or 20 percentwhen orange juice is refrigerated

478 orange