Prevalence of obesity and associated risk factors in chinese pre school children aged 6 to 72 months old in singapore 4

DISCUSSION 4.1 Summary of the study Our study, part of a large population-based study titled “Strabismus, Amblyopia and Refractive Error in Singapore Chinese Preschoolers STARS,” highl

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CHAPTER 4

4 DISCUSSION

4.1 Summary of the study

Our study, part of a large population-based study titled “Strabismus, Amblyopia and Refractive Error in Singapore Chinese Preschoolers (STARS),” highlights the prevalence of overweight and obesity and its associated risk factors

in Chinese preschool children aged 6 to 72 months in Singapore

The prevalence of overweight was 8.1% (“CDC BMI for age” reference), 7.6% (“IOTF BMI for age” reference) and 7.0% (“Singapore BMI for age” reference) The prevalence of obesity was 7.1% (“CDC BMI for age” reference), 3.9% (“IOTF BMI for age” reference) and 5.3% (“Singapore BMI for age” reference) Based on the “CDC BMI for age” reference, the prevalence of obesity

in Chinese preschool children in the STARS was comparatively lower than that of children from the United States,57 Chile,,61,62 and Italy63

Our results showed that the prevalence, using the “IOTF BMI for age” reference, probably underestimated the overweight and obesity problem in our local paediatric population compared to the “CDC BMI for age” reference However, the estimated prevalence of overweight and obesity based on the “CDC BMI for age” and “Singapore BMI for age” references were comparable, even though the cutoffs used to define overweight and obesity by the “Singapore BMI

4.2 Prevalence of obesity

Although the prevalence of obesity and its associated factors in aged children (<6 years old) has been reported by other countries for their populations, the present study is one of few in Singapore to estimate the prevalence of overweight and obesity and evaluate the associated risk factors in young Chinese preschool children, specifically, those aged 6–72 months

preschool-It is important to compare the prevalence of obesity with the similar aged group from different countries (the United States, Germany, Chile, Italy, Canada and Jordan) with Singapore Chinese because it may highlight the status of

“IOTF BMI for age” reference The Chinese study evaluated children aged 3.5–6.4 years (n=262,738), born between 1993 and 1996 to a mother residing in one

of the defined study areas (northern rural, southern rural and urban area of China) for at least one year However, the Chinese study did not specify the response rate

In contrast, the sampling method used in the Chinese study,54 including all children who were born between 1993 and 1996 to mothers residing in one of the defined study areas for at least one year, was more complete compared to our study However, although height and weight measurements were done by locally trained health workers using standardized measuring procedures, the Chinese study did not indicate the number of health workers who participated in each of the three study areas Therefore, the inter-observer variability in the Chinese study cannot be assessed Although the instruments used in the study were all calibrated, it did not specify whether the instruments used in different study sites

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were calibrated against each other, using the same weights, to ensure there were

no discrepancies in measurements Both the Chinese study and our study used standardized measuring procedures at all study sites which were administered by trained health workers

Although both the Chinese study and our study conducted in Chinese preschool aged children, we cannot expect to have the similar prevalence between China and Singapore because there might be differences in the environmental factors and life styles between two countries

Germany

A German study performed by Kalies et al (2002)60 found 2.8% of the prevalence of obesity, using the “IOTF BMI for age” reference The Germany study was conducted in 126,083 children aged 5–6 years who participated in the school health examination and had a response rate of 97.1% Comparing similar age groups (60.0–72.0 months), the prevalence of obesity (boys=7.2% and girls=4.9%) in our study was higher than that in Germany (2.8% for both boys and girls) Therefore, the prevalence of obesity was higher in our study than that

in the Germany study, and this was more pronounced when we compared the same age groups The differences in the study design, i.e ours being population-based while theirs is a school-based study design may be one of the reasons involved in the lower prevalence of obesity in Germany

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Countries with higher prevalence compared to Singapore

Based on the “CDC BMI for age” reference, the prevalence of obesity in our study was lower than that in the United States,57 Chile,61 Italy63 Furthermore, based on the “IOTF BMI for age” reference, the prevalence was also higher in Jordan,56 Canada,59 Chile62 and Italy63, compared to our study

Although the studies from Chile,61,62 Italy,63 Jordan,56 Canada59 had fairly large sample sizes, they were not population-based studies These studies were conducted in children who underwent obligatory health examinations when entering kindergarten or first grade Therefore, the children who attend preschool were more likely to be from the middle or high income families and that factor could contribute to the higher prevalence compared with our population-based study

The United States

The population based study conducted in the United States57 described a prevalence of obesity as 10.4% (using the CDC reference) for children aged 2 to 5 years (n=3,281) who were included in NHANES (2007-2008), a continuous programme which assess a variety of health and nutrition measurements of children and adults in the United States The prevalence of obesity from this study was higher than that of our study (10.4% vs 7.1%) The higher prevalence

of obesity in the United States was expected because it is a more urbanized country and it adopts more sedentary life styles for many years, compared to Singapore

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Chile

Stanojevic et al (2008)61 conducted a study in children (n=25,013) aged 2–5 years from the Junta Nacional de Jardines Infantiles programme (one of the national food supplementation programme) and found the prevalence of obesity was 16.35% using the CDC reference Although the age range used in the Chilean study was similar to our study of 6–72 months old children, participating children

in the study were from low and middle income families who registered with the programme and the Chilean study did not specify the study’s response rate Thus, they might not be representative of all the preschool-aged children in Chile Using the CDC reference, the prevalence of obesity was about two times higher in the Chilean study than our study of Chinese preschool children (16.35% vs 7.1%)

Another school-based study in Chile62 included a large sample of 6–year–old first grade children (n=199,444) and evaluated the prevalence of obesity using three criteria (CDC and IOTF references and weight–for–height z-scores.) Based

on the CDC reference, the prevalence of obesity in the Chilean study was 14.7% and 15.8% for boys and girls, respectively, approximately two times higher for boys (14.7% vs 8.3%) and three times higher for girls (15.8% vs 5.7%) than the counterparts in our study Comparing a similar age group (60.0–72.0 months) in our study with the 6–year–olds in the Chilean study, the prevalence of obesity for girls in our study was also approximately half that found in the Chilean study (8.1% vs 15.8%) However, the prevalence of obesity in boys aged 6 years was similar (12.8% vs 14.7%) in both studies

in both studies Therefore, the prevalence of obesity in Singapore was lower than that in Chile62, comparing the overall as well as the similar age groups

Italy

Maffeis et al (2006)63 conducted a study in Italy of 2,150 children aged 2–

6 years The prevalence of overweight and obesity was evaluated using three criteria (the CDC and IOTF references and Italy’s National BMI reference tables) The study utilized the same standardized methodology which was performed by two teams of paediatricians at two study sites (located at the northeast and south

of Italy) The study achieved a high response rate of 89.6% and children were randomly selected from the registers of kindergartens at the two study areas Using the “CDC BMI for age” reference, the prevalence of obesity for children aged 2–6 years in Italy was about two times higher than that of our study (16% vs 7.1%) A similar result was found, using the “IOTF BMI for age” reference: the

of our study

Canada

Based on the “IOTF BMI for age” reference, a study conducted by Canning et al (2004)59 (n=4,161) from Canada showed a higher prevalence of obesity than that in the present study The targeted population was children (born

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in 1997 in the province of Newfoundland and Labrador) who participated in the Preschool Health Programme The response rate varied by regions and ranged from 73.0% to 84.0% The prevalence of obesity in the Canada study was two times higher than that of our study (boys= 7.8% vs 4.6% and girls= 8.2% vs 3.2%)

Summary of prevalence in comparison

Using the “IOTF BMI for age” reference, our study had a slightly higher prevalence of overall overweight/obesity in Singapore Chinese preschool children than that of the Chinese study54 and the Germany study60

The slight different in the overall prevalence of overweight/obesity between our study and the Chinese study54 may be due to the age differences between these two studies (based on the “IOTF BMI for age” reference; 2 to ≤6 years in the present study and 3.5–6.4 years in the Chinese study) Another possible reason is the methodological constraints in the two studies Although both studies used standardized measuring procedures, the instruments used may not be the same Our study used the Seca-220 as the instrument to measure height and weight for children who were 2 years old and above Unfortunately, the Chinese study54 did not mention the name and model of instrument used to measure height and weight in their study

One possible explanation for the lower prevalence in Singapore Chinese preschool children as compared to the children in Jordan,56 the United States,57

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Canada,59 Chile,61,62 and Italy63 is the difference in lifestyles, quantity and quality

of nutrient intake between the Western people and the Chinese

Another possible reason is that the “CDC BMI for age” reference was based on the American population and that standard or yardstick may not accurately reflect the prevalence of obesity among different populations form other countries, where people have different body compositions and cultural behaviors

4.2.1 Age

Our study showed an increasing trend of prevalence of obesity with age for both genders based on the “CDC BMI for age” and “IOTF BMI for age” reference (p=<0.001 for both references) However, no specific trend was present for prevalence of overweight with age in our study

This increasing trend of prevalence of obesity with age was also found in the Chile study61 (using the “CDC BMI for age” reference) although the Canadian study59 (using the “IOTF BMI for age” reference) did not find significant differences between different age groups in the prevalence of overweight or obesity

Interestingly, the Chinese study54 (based on the “IOTF BMI for age” reference), demonstrated an inverse trend of prevalence of overweight/obesity with age in both boys and girls The Chinese study was a population-based study conducted on children aged 3.5–6.4 years (n=262,738) from the northern rural,

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southern rural and urban areas of China In contrast, another study from China performed by Jiang J et al (2006)66 (n=930) showed an increasing trend of the prevalence of obesity with age The Chinese study66 was conducted in children aged 2–6 years from randomly selected five large kindergartens in two urban districts of Beijing, China (response rate=89.1%)

Insignificant difference between the age groups in the prevalence of overweight or obesity (p≥0.05) was reported in the Canada study59 (n=4,161) The study included children aged 3.5–5.5 years (born in 1997) from the province of Newfoundland and Labrador who participated in the preschool health check programme There was no trend of increasing prevalence of overweight with age, which was consistent with our study, whereas, for the prevalence of obesity, the Canadian study did not have an increasing trend as age increased, as observed in the present study

Nevertheless, the consistent finding of increasing prevalence of obesity with age was seen in the Chilean study61 (n=25,013) The Chilean study described the cross-sectional obesity trends in Chilean preschool children aged 2–5 years who participated in the Junta Nacional de Jardines Infantiles programme (one of the national food supplementation programme) from 1996 to 2004 The results from the Chilean study showed that the prevalence of obesity increased with age (OR 1.04, 95% CI: 1.038,1.047), and the odds of obesity increased by approximately 10% for each year (test for trend OR 1.08, 95% CI: 1.07,1.09, p<0.001) increment during the 9-year study period from 1996 to 2004 Although both the Chilean and our studies conducted prevalence surveys on large sample

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sizes, the Chilean study was not a population-based study and its response rate was also not mentioned However, both studies showed a consistent increasing trend in the prevalence of obesity with age in preschool children

In our study, the prevalence of overweight and obesity were the highest in the age group of 60.0–72.0 months in both genders based on the “CDC BMI for age” and “IOTF BMI for age” references These findings were consistent with the adiposity rebound of approximately 6 years of age.78 In this second period of rapid growth in body fat, both the size and number of adipocytes increase,79,80 and

it may be the reason for the highest prevalence of overweight and obesity in this age group of 60.0–72.0 months among the 24.0–72.0 months in our study

Using the “Singapore BMI for age” reference, the prevalence of obesity was highest in the youngest age group (6.0–11.9 months) among the 6.0–72.0 months for both genders This result is consistent with the first period of rapid growth in the size of the adipocytes during the first year of life.79,80 This finding cannot be seen for the “CDC BMI for age” and “IOTF BMI for age” references because both references cannot be applied in children less than 2 years old However, using the “Singapore BMI for age” reference, the second period of increased adiposity was still not present in the oldest age group (60.0–72.0 months)

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4.2.2 Gender

Our study showed that boys were more likely to be obese than girls (p=0.03), using the “CDC BMI for age” reference However, the prevalence of obesity, based on the “IOTF BMI for age” and the “Singapore BMI for age” references, did not show gender differences (p=0.13 and 0.94, respectively)

As for the prevalence of overweight, there were no statistically significant differences between genders using all three references in our study (p=0.10 for the

“CDC and IOTF BMI for age” references and p=0.39 for the “Singapore BMI for age” reference) Our results were consistent with that of the studies from the United States57 and Canada59 Nevertheless, using the “IOTF BMI for age” reference, our study had inconsistent results compared to other studies from Italy63 and China54 Similarly, there was an inconsistent result compared to the Chilean study, using the “CDC BMI for age” reference. 61

In the United States, a study conducted by Ogden et al.57 in children aged

2 to 5 years (n=3,281), using the “CDC BMI for age” reference, showed no gender differences in the prevalence of overweight, and this result was consistent with ours The data were derived from NHANS 2007-2008

The Canadian study59 analysed 4,161 children aged 3–5 years (born in 1997) who enrolled in the preschool health check programme in 2002 Using the

“IOTF BMI for age” reference, there were no significant differences between genders in the prevalence of overweight or obesity (p=≥0.05)

Gender differences were shown in the study conducted by Maffeis et al (2006)63 in 2,150 children aged 2–6 years who were randomly selected from a

be overweight or obese than boys (OR=1.14, 95% CI: 1.11,1.17) Using the same reference (“IOTF BMI for age” reference), their findings were different from ours, i.e there were no gender differences in the prevalence of overweight or obesity

Using the “CDC BMI for age” reference, a study from Chile (2008)61 also observed an inconsistent result of gender differences in the prevalence of overweight in Chilean preschool children (n=25,013) as compared to our study The Chilean study included children aged 2 to 5 years participating in the Junta Nacional de Jardines Infantiles programme (one of the national food supplementation programme) and showed that the prevalence of overweight was higher in girls (OR=1.26, 95% CI: 1.038,1.047) than boys

Overweight and obesity are multi-factorial etiologic weight related statuses Therefore, all environmental factors and genetic factors may influence the prevalence in genders For example, boys are more favored than girls in Chinese tradition, and this may also be one of the possible explanations Other possible reason is boys may eat more than girls or girls are pickier in eating than boys Moreover, different parental upbringing patterns may also affect the eating habits of children

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Another possible indirect explanation is the statistically significant (p=<0.001) greater mean birth weight of boys (3,137.8 grams) as compared to girls (3,036.7 grams) found in our study The consistent finding of statistically significant gender difference in birth weight were also reported in other studies.81-83

Thus, higher birth weight in boys may also explain the higher prevalence of obesity in boys than girls in our study

4.3 Associated factors for overweight or obesity

Obesity and its weight-related health problems are important health issues

in all countries because of its causal effect on increasing morbidity and mortality Therefore, evaluating the causes of obesity [i.e; energy imbalance between energy intake (diet) and energy expenditure (physical activity)] such as insufficient energy expenditure, excessive snacking and excessive eating of fast food diet is the main key factor in prevention of overweight/obesity On the other hand, understanding the associated factors is helping to generate hypotheses for testing causal factors To implement effective prevention and intervention, evaluation of either the causes or associated factors in early life play an important role Prior studies from other countries have investigated the very early risk factors for overweight and obesity in preschool-aged children Likewise, our study examined the influences of the risk factors on the overweight/obesity in Singapore Chinese preschool children The possible predictors include birth weight, maternal pre-natal history (maternal smoking and alcohol consumption during pregnancy),

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breastfeeding, behavioral factors of the child (physical activities and sedentary activities) and socioeconomic status (father’s education, mother’s education, total combined monthly income)

4.3.1 Birth Weight

Birth weight, a possible surrogate of intrauterine environment and foetal growth, is believed to be one of the potential risk factors for BMI and overweight/obesity status in childhood Therefore, many studies have evaluated the association of birth weight and weight status in childhood In our study, birth weight was positively associated with overweight, obesity and overweight/obesity (p=<0.001) in univariate analysis

In logistic regression analysis, the association of birth weight with overweight/obesity remained significant (p=<0.001) after adjusting for age, gender, father’s education, number of hours per day the child spent at preschool, and time spent in sedentary activities

In addition, the association of birth weight and BMI was analysed using a linear regression model The results showed a relationship between birth weight and BMI (p=<0.001), after adjusting for age, gender, father’s education, number

of hours per day the child spent at preschool, and time spent in sedentary activities

A similar result was shown by a cross-sectional studyconducted on 1,412 preschool children from both public and private nursery schools in five districts of

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Cyprus (response rate=70.6%).68 Consenting parents were asked to quote the information of birth weight from a health booklet The categories of birth weight were defined differently from the present study, and the distribution of birth weight was higher in the Cyprus study as compared to our study The highest birth weight group was defined as >4,000 grams in the Cyprus study, compared to

≥3,390 grams in our study Therefore, we compared the ‘3,501–4,000 grams’ category with that of the highest quartile (≥3,390 grams) in our study The results from the Cyprus study showed that the odds of being obese for birth weight between 3,501–4,000 grams (defined by the IOTF reference) in children aged 2.0–6.9 years was 4.61 times greater than that of birth weight between 2,501–3,000 grams (p=0.003) after adjusting for age and sex This OR (4.61) was similar

to the OR found in our study (4.19) in which the odds of obesity was compared for birth weight ≥3390 grams versus birth weight <2,825 grams (p=< 0.001)

Another consistent result was shown in the study by Moschonis et al (2008)69 from Greece (n=2,374) The results showed a positive association between birth weight and overweight (≥95th percentile) in children aged 6 and 12 months This study derived the data from GENESIS (the Growth, Exercise and Nutrition Epidemiological Study In pre-Schoolers): a cohort study of children aged 1–5 years from randomly selected public and private nurseries as well as day care centres within municipalities in five counties in Greece Their study’s response rate varied from 54 to 95% The birth weight categories defined in the Greek and present studies were different The Greek study grouped three categories of children into born as: small for gestational age (<10th percentile);

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appropriate for gestational age (10th–89th percentile); and large for gestational age (≥90th percentile) The results showed that the odds of being overweight (≥95thpercentile) at 6 and 12 months of age were 4.59 and 2.19, respectively when children born large for gestational age were compared to those born appropriate for gestational age However, the positive association was not seen in the 1–to–3–year–old– and 3–to–5–year–old–age groups in the Greek study

There is a general understanding that a more favourable intrauterine environment leads to higher birth weight, except for macrosomia seen in infants

of diabetic mothers Many believe that the foetus in utero adapts himself/herself

to the conditions during gestation Thus, many studies have focused on factors of prenatal and perinatal period such as maternal obesity, nutrition, behavioral, and psychological factors Children who was exposed to famine in utero or who experienced maternal restraint in utero were delivered with low birth weight and among those who developed ‘catch-up’ growth in the first two years of life are more likely to be overweight/obese at five years of age.84,85 However, most low birth weight infants are likely to remain shorter and lighter in early childhood than children with high birth weights despite accelerated weight gain in the first year

of life.85 On the other hand, high birth weight children remain taller and heavier than their normal birth weight counterparts. 85

In overall, intrauterine ‘programming’ 86 as well as genetic factor might play important roles in determining the weight at birth Nevertheless, the positive relationship between birth weight and overweight or obesity in later life is still puzzling In high birth weight infants compared to normal birth weights, there

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might be some differentiation in the hypothalamic centre which regulates food intake or in adipocyte regulation.87 Therefore, there is still a gap and further research is needed to reveal the fundamental background understanding of the positive association between birth weight and overweight/obesity in childhood

In addition, studies had suggested that the associations between birth weight and BMI or overweight/obesity did not necessarily reflect high adiposity

in high birth weight infants.88 Many studies suggested that the positive association between birth weight and BMI could result from increasing lean body mass rather than adiposity.89-93 The fact was affirmed in preschool children by Hediger et al from the US (1998).93 The results showed that in ‘large for gestational age’ children, excess adiposity was less than excess muscularity Therefore, further research is needed to investigate more details of the association between birth weight and adiposity as well as muscularity

4.3.2 Duration of sedentary activities (Total sedentary activities,

Watching television) per day

Low energy expenditure is one of the most widely cited etiologic factors for overweight or obesity The results of our present study showed that sedentary activities/watching television were positively associated with the likelihood of overweight/obesity This positive relationship was also seen in France,64 China,66 and Japan.72

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Among the studies with consistent positive associations, the study conducted by Lioret et al (2007)64 was the first nation-wide study; it included 1,016 children aged 3 to 14 years in France Participating children were grouped into preschool (3–5 years old), primary (6–10 years old) and secondary (11–14 years old) school levels This study showed that sedentary behaviour, in this case, time spent either watching television or playing video-games in an ordinary week was positively associated with overweight (defined by the “IOTF BMI for age” reference) in children aged 6 to 14 years However, this positive association was not found in children aged 3 to 5 years The adjusted odds of being overweight for longer sedentary time were 2.1 (0.7–6.6) in children aged 3–5 years and 2.3 (1.1–4.8) in children aged 6–14 years compared to their counterparts who had shorter sedentary time

Another study was conducted by Jiang et al (2006),66 evaluating the risk factors for overweight in children 2 to 6 years old (n=930) who were randomly selected from five large kindergartens in two urban districts in Beijing, China The Chinese study showed a significant association between television hours and overweight (defined by the “IOTF BMI for age” reference) In this study, children who watched television more than 2 hours per day had 1.56 times (1.17–2.09) greater odds for being overweight compared to those who spent less than 2 hours watching television per day Our present study did not observe an association between television watching per day and overweight but found associations with obesity and combined overweight and obesity In the linear regression analysis of our present study, the association of time spent watching television with BMI

More time spent in sedentary behaviour indirectly means less habitual physical activity energy expenditure Watching television is one of the most common sedentary behaviours in children in developed countries Furthermore, advancing technologies has allowed for the creation of attractive programmes that enable children to become addicted to watching television for longer times In this way, children spend more time watching television and increase the number of sedentary hours per day Moreover, some sedentary behaviours such as reading or watching television may promote consumption of unhealthy snacks or soft drinks which aggravates obesity even further

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4.3.3 Duration of preschool hours per day

Obesity as well as combined overweight and obesity were negatively associated with the number of hours per day the child spent at school This association may have been first analysed in Singapore, where it showed the protective effects of preschool on the likelihood of obesity or overweight/obesity

In Singapore, the daily programme for preschool includes preparing children for formal education, and developing personal and social skills by involving them in games, music and outdoor play.94 Therefore, children who go to preschool might be exposed to more physical activities, compared to those who stay at home Finn K et al (2002) showed that child care centre was a determinant factor in predicting physical activity in children.95 There was also an association between the area (square footage) of childcare centre and percentage of body fat among 12-month-old infants.96

In addition, the preschools often provide meals to children in full-day programmes In 2005, the Health Promotion Board (HPB) collaborated with the Family Services Department of the Ministry of Community Development, Youth and Sports (MCYS) to introduce the “Healthy Eating in Child Care Centres Programme”.97 As of October 2009, 240 child care centres in Singapore (out of 777) achieved the “Healthy Eating in Child Care Centres Award. 98,99 The programme includes assessment of key dietary needs and how nutritional education is taught in the classroom, provides training for childcare centre supervisors and cooks, and gives a yearly evaluation by the HPB.100 Therefore,

4.3.4 Physical activities

Among the three basic component of energy expenditure: resting energy expenditure (REE), thermal effect of food (TEF) and voluntary physical activity, physical activity is the most variable and modifiable component of energy expenditure.101 REE remains relatively stable provided that an individual’s weight and health status unchanged.101 In addition, TEF is the energy expenditure used in the digestion of food consumed, and it is relatively small with the total daily energy expenditure.101 Therefore, the absence of physical activities alone can represent the absence of energy expenditure, leading to an increase in the body fat content

There were different results from different studies regarding the association of physical activities and child overweight.64,66 However, in our study, playing outdoors (p=0.25) and outdoor leisure activities (p=0.31) were not found

to be associated with overweight/obesity The possible reasons for different results between studies are the variations in methods which physical activity is measured and the design of the studies

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4.3.5 Other factors

The present study did not find an association of overweight/obesity with mother education, income, breastfeeding and maternal smoking or alcohol consumption during pregnancy However, some studies have reported an association of the abovementioned factors with overweight or obesity 65,66,69 while others have not.67,68 Moreover, in our study, only watching television appeared as

an associated factor with overweight/obesity while other sedentary activities (playing computer/television/hand held video games and reading, drawing and coloring activities) were not found to be associated with overweight/obesity

4.4 Strengths of the study

The current study is among the few studies, evaluating the prevalence of obesity in the very young age group (6– to 72–month–old) Our present study also examines the associated early risk factors of obesity in preschool Chinese children aged 6– to 72–month–old in Singapore

This is a population-based study with a large sample size of children (3,009) and a good response rate (72.3%) from the large study area of South-Western and Western parts of Singapore This shows that selection bias is minimized, and it can also be regarded as one of the strengths of our study

Regarding measuring the height and weight, all staffs in the study were trained to perform the same standardized measurement procedures and methods in

4.5 Limitations of the study

The main limitation of the current study is the use of BMI to estimate body fatness Although it is a common, inexpensive and practical method of obesity measurement, it cannot distinguish between body fatness and muscularity Therefore, the accuracy and preciseness in determining body fat, using BMI, cannot be as accurate and precise as using dual energy X-ray absorptiometry (DEXA), the bioelectrical impedance analysis, computed tomography (CT/CAT scan), or magnetic resonance imaging (MRI/NMR)

The equipment used to measure height and weight in the two different study sites were calibrated separately at its respective study site Therefore, the validity of accurate and precise measurement cannot be ignored

In the current study, exposure misclassification may occur when asking questions about physical and sedentary behaviours because the interviewer is aware of the estimated weight of the participating children Therefore, the

Overall, the cross-sectional nature of this study is one of the limitations, and the present study cannot establish a cause-effect relationship of the associations Therefore, we cannot conclude that overweight/obesity in 6– to 72–month–old Singapore Chinese children was caused by the associated factors found in the current study

4.6 Recommendations

Obesity and its weight-related health consequences are important public health problems Although our study showed that the prevalence of overweight/obesity in Chinese preschool children in Singapore was lower than that of most Western countries, prevention and control of overweight/obesity in the paediatric population in Singapore are crucial to ensure improved health of Singaporeans Although our study data cannot provide identification of appropriate interventions, there are some general recommendations that may be helpful for interventions

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Implementing screening programmes of overweight/obesity for children who enter preschools could also help in identifying high-risk children Moreover, identification of children with a high risk of overweight/obesity could also be performed by using associated factors such as male gender, higher birth weight, longer television watching time and longer sedentary activity time, as found in our study At the family level, when children are at home, they should minimised watching television or engaging in sedentary activities

Performing physical exercise is usually a planned and structured activity However, this may not be suitable for preschool-aged children Preschool-aged children should be encouraged to perform physical activities, defined as any bodily movement produced by skeletal muscles,102 instead of “physical exercises”

to prevent obesity The National Association for Sport and Physical Education (NASPE) from the United States established a statement of guidelines for physical activity in children birth to five years 103 It stated that movements of infants (birth to 12 months) should not be restricted, and toddlers and preschoolers should engage in both structured and unstructured physical activity

in indoor as well as outdoor areas, provided with the safety settings,.103 Thus, parents and caregivers should be encouraged to let children make movements regularly, and preschool teachers in child care centres should encourage their pupils to be involved in physical activities both in the classroom and outdoors However, the advanced technology nowadays (for example: video games, handheld games and animated cartoons) and weather in Singapore may be the common barriers to encourage children to make physical activities

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Future studies should be conducted on all ethnicities of preschool-aged children in Singapore to evaluate the prevalence of overweight and obesity, and to compare the prevalence of overweight and obesity in preschool children among different ethnicities in Singapore Levels of risk could be identified in the prevalence of overweight and obesity among ethnic groups in Singapore to plan the strategies for the intervention of weight-related health problems

Our study is a cross-sectional study and temporal relationships between exposures and overweight and obesity cannot be ascertained Therefore, further cohort studies are needed to identify causal factors of overweight and obesity in Singapore preschool-aged children

4.7 Conclusions

In summary, our present study provides data of the prevalence of overweight and obesity and associated early risk factors in a very young age group (6– to 72–month–old) of Singapore Chinese children The prevalence of overweight and obesity are 8.1% and 7.1%, respectively, among preschool-aged Chinese children in Singapore There is a trend of increasing prevalence of obesity as the age increases, but no such pattern is found in those in the overweight category

Boys are more likely to be obese than girls although there is no gender differences for the prevalence of overweight Birth weight and time spent on sedentary activities show positive association while duration of preschool hours

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shows negative association with overweight/obesity Preventive and health educational programmes; healthy eating programmes, weight reduction programmes or physical activity programmes should be considered as ways to reduce the prevalence of overweight and obesity and subsequent short term and long term complications Further studies of the prevalence of overweight and obesity and the early associated factors should be conducted in multiethnic preschool-aged children in Singapore