Diagnostic accuracy of anthropometric indices for obesity screening among Asian adolescents.

INTRODUCTION: Weight-and-height-based anthropometric indices have long been used for obesity screening among adolescents.However, the ability of their age-and-sex-specific reference values in classifying adolescent as "obese" in different populations was not fully established. Our study aimed to validate the existing international (BMI-for-age charts from WHO, CDC, IOTF) and local cut-offs [percent weight for height (PWH)] for obesity against body fat percentage, as assessed by 4 skinfolds measurement. MATERIALS AND METHODS: A cross-sectional sample of 6991 adolescents aged 12 to 18 years was measured. All anthropometric measurements were compliant with the internationally accepted protocol. Obesity was defined as percentage body fat greater than or equal to 95 percentile, specific to age and sex. The validity of the existing classification criteria in detecting obesity was evaluated by comparing their respective diagnostic accuracy. RESULTS: Both prevalence of obesity and diagnostic accuracy indices varied by the classification criteria. While all criteria generated very high specificity rates with the lowest being 95%, their sensitivity rates were low ranging from 43% to 71%. Youden's index suggested that CDC and WHO criteria had optimal sensitivity and specificity. ROC analysis showed that overall performance could be improved by refining the existing cut-offs. CONCLUSIONS: Clinical validity of weight-and-height-based classification systems for obesity screening in Asian adolescents is poorer than expected, and this could be improved by refining the existing cut-offs.

Review on epidemic of obesity.

There has been a growing concern about obesity worldwide. We performed a review on the prevalence and trends of obesity among adults and children. We reviewed the data on the prevalence of adult obesity and being overweight from the Global Database on Body Mass Index on the World Health Organisation (WHO) Website and prevalence of children being overweight from the International Obesity Task Force website. Various databases were also searched for relevant reviews and these include PubMed, EMBASE, NHS CRD databases and Cochrane. The prevalence of obesity is high in many parts of the world. Generally, there is an increasing trend of prevalence of adult obesity with age. The peak prevalence is reached at around 50 to 60 years old in most developed countries and earlier at around 40 to 50 years old in many developing countries. Obesity is a major health concern. Appropriate strategies need to be adopted to tackle obesity which itself brings about significant disability and premature deaths. Further observation may be needed to see if the trend of prevalence abates or increases in the near future.

Rationale for redefining obesity in Asians.

INTRODUCTION: There has been extensive research on defining the appropriate body mass index (BMI) cut-off point for being overweight and obese in the Asian population since the World Health Organisation (WHO) Expert Consultation Meeting in 2002. MATERIALS AND METHODS: We reviewed the literature on the optimal BMI cut-off points for Asian populations. We searched PubMed, EMBASE, National Institute for Health Research Centre for Reviews and Dissemination (NHS CRD) Database, Cochrane Library and Google. Attempts to identify further studies were made by examining the reference lists of all retrieved articles. There were 18 articles selected for the review. RESULTS: There were 13 studies which have identified the BMI cut-off points for Asian populations lower than the international BMI cut-off points recommended by the WHO. Many of the studies have recommended lowering BMI cut-off point specific for Asian populations. A few studies concurred with the recommended cut-off point for Asian populations recommended by International Association for the Study of Obesity (IASO), the International Obesity Task Force (IOTF) and the WHO in 2002. Asian populations were also noted to have higher cardiovascular risk factors than Western populations at any BMI level. CONCLUSIONS: Further research would be needed to look at the all-cause mortality at same BMI levels between Asians and Caucasians in order to evaluate the BMI cut-off recommendations for Asian populations. It is necessary to develop and redefine appropriate BMI cut-off points which are country-specific and ethnic-specific for Asians. These will facilitate the development of appropriate preventive interventions to address the public health problem posed by obesity.

Performance measures for mental healthcare in Singapore.

Mental disorders are both common and costly. The mental health system in Singapore lacks co-ordination as well as being underdeveloped in certain areas. To address these gaps as well to face emerging challenges like an ageing population, and other socioeconomic changes, the Ministry of Health of Singapore has commissioned a Committee to formulate a 5-year Mental Health Policy and Blueprint. A task group has been formed to implement this blueprint and evaluation of these various initiatives with performance measures are inevitable. The choice of these measures, however, can be a daunting task with the various and diverse interests of multiple stakeholders. This paper describes the process of choosing the relevant measures with the appropriate attributes, and suggests a framework, which can serve as a guide for selecting mental health performance measures.

3rd College of paediatrics and child health lecture--the past, the present and the shape of things to come

The growth trends of Singapore children spanning 5 decades are reviewed, based on 8 anthropometric studies from 1957 till 2002. The heights of pre-school children and school age children appear to have optimised according to their genetic potential, but the weights and body mass indices of children still appear to be increasing from 6 to 18 years for both sexes, probably as a consequence of increasing affluence. This trend is reflected in the increasing obesity prevalence in school children over the past 30 years, and the concomitant increased morbidity associated with the metabolic syndrome, necessitates further research into the causes of obesity. Barker's hypothesis first suggested that changes in the intra-uterine environment can cause fetal adaptations which persist into adulthood, and are responsible for many chronic diseases of adult life. More recently, intense research in the field of epigenetics suggests that the environment can also influence the phenotype through gene expression, through modification of DNA methylation and histones which, in turn, influences gene expression. The challenge for the future is to determine if there are clear epigenetic changes, which are responsible for the increased prevalence of childhood and adolescent obesity, and whether these changes are transmitted through generations. Unravelling these epigenetic mechanisms may be the key to the prevention of obesity and the metabolic syndrome.

Perilipin gene variation determines higher susceptibility to insulin resistance in Asian women when consuming a high-saturated fat, low-carbohydrate diet.

OBJECTIVE: To investigate the association between genetic variation in the adipocyte protein perilipin (PLIN) and insulin resistance in an Asian population as well as to examine their modulation by macronutrient intake. RESEARCH DESIGN AND METHODS: A nationally representative sample (Chinese, Malays, and Indians) was selected in the Singapore National Health Survey following the World Health Organization-recommended model for field surveys of diabetes. A total of 1,909 men and 2,198 women (aged 18-69 years) were studied. Genetic (PLIN 11482G-->A and 14995A-->T), lifestyle, clinical, and biochemical data were obtained. Homeostasis model assessment of insulin resistance (HOMA-IR) was used to evaluate insulin resistance. Diet was measured by a validated food frequency questionnaire in one of every two subjects. RESULTS: We did not find a significant between-genotype difference in insulin resistance measures. However, in women we found statistically significant gene-diet interactions (recessive model) between PLIN 11482G-->A/14995A-->T polymorphisms (in high linkage disequilibrium) and saturated fatty acids (SFAs; P = 0.003/0.005) and carbohydrate (P = 0.004/0.012) in determining HOMA-IR. These interactions were in opposite directions and were more significant for 11482G-->A, considered the tag polymorphism. Thus, women in the highest SFA tertile (11.8-19%) had higher HOMA-IR (48% increase; P trend = 0.006) than women in the lowest (3.1-9.4%) only if they were homozygotes for the PLIN minor allele. Conversely, HOMA-IR decreased (-24%; P trend = 0.046) as carbohydrate intake increased. These effects were stronger when SFAs and carbohydrate were combined as an SFA-to-carbohydrate ratio. Moreover, this gene-diet interaction was homogeneously found across the three ethnic groups. CONCLUSIONS: PLIN 11482G-->A/14995A-->T polymorphisms modulate the association between SFAs/carbohydrate in diet and insulin resistance in Asian women.

The V227A polymorphism at the PPARA locus is associated with serum lipid concentrations and modulates the association between dietary polyunsaturated fatty acid intake and serum high density lipoprotein concentrations in Chinese women.

Peroxisome proliferators activated receptor alpha (PPARalpha) regulates the transcription of several proteins involved in human lipoprotein metabolism. We screened the PPARA locus for polymorphisms in 20 unrelated subjects from each of three ethnic groups (Chinese, Malays and Asian Indians). Only the V227A polymorphism was observed. We genotyped 4248 subjects (2899 Chinese, 761 Malay and 588 Asian Indians) and found allele frequencies for the A227 allele of 0.04 in Chinese, 0.006 in Malays and 0.003 in Asian Indians. We examined the associations between this polymorphism and serum lipid concentrations in Chinese. In women, but not in men, the presence of the A227 allele was associated with lower serum concentrations of total cholesterol [5.38mmol/l (95%CI: 5.22-5.54) versus 5.21mmol/l (95%CI: 4.99-5.43), p=0.047] and triglycerides [1.19mmol/l (95%CI: 1.10-1.28) versus 1.09mmol/l (95%CI: 0.98-1.21), p=0.048]. We also found that the V227A polymorphism modulates the association between dietary polyunsaturated fatty acid intake and serum high density lipoprotein concentration (p-value for interaction=0.049). Our findings implicate PPARalpha in the lipid lowering associated with diets high in PUFA and suggests that genetic variation at the PPARA locus may determine the lipid response to changes in PUFA intake.

Differential effects of the C1431T and Pro12Ala PPARgamma gene variants on plasma lipids and diabetes risk in an Asian population.

We investigated the association of C1431T and Pro12Ala polymorphisms at the peroxisome proliferator-activated receptor gamma (PPARgamma) locus with plasma lipids and insulin resistance-related variables, according to diabetes status, in a large and representative Asian population from Singapore consisting of 2,730 Chinese, 740 Malays, and 568 Indians. Moreover, we estimated the diabetes risk and examined gene-nutrient interactions between these variants and the ratio of polyunsaturated fatty acid to saturated fat (SFA) in determining body mass index (BMI) and fasting insulin. We found differential effects of these gene variants. The Pro12Ala polymorphism was more associated with plasma lipids and fasting glucose concentrations, whereas the C1431T polymorphism was related to the risk of diabetes. Carriers of the 12Ala allele had higher HDL-cholesterol than did Pro12Pro homozygotes (P < 0.05), and the effect of the 12Ala allele on fasting glucose was modified by diabetes status (P < 0.001). After controlling for confounders, carriers of the T allele had decreased risk of diabetes compared with CC homozygotes [odds ratio (OR) 0.73, 95% confidence interval (CI) 0.58-0.93; P = 0.011]; this effect was stronger in Indians (OR 0.38, 95% CI 0.15-0.92; P = 0.032). For both polymorphisms, normal subjects carrying the less prevalent allele had higher BMI (P < 0.05). The PUFA/SFA did not modify the effect of these polymorphisms on BMI or insulin.

Dietary fat interacts with the -514C>T polymorphism in the hepatic lipase gene promoter on plasma lipid profiles in a multiethnic Asian population: the 1998 Singapore National Health Survey.

We have previously reported an interaction between -514C>T polymorphism at the hepatic lipase (HL) gene and dietary fat on high-density lipoprotein-cholesterol (HDL-C) metabolism in a representative sample of white subjects participating in the Framingham Heart Study. Replication of these findings in other populations will provide proof for the relevance and consistency of this marker as a tool for risk assessment and more personalized cardiovascular disease prevention. Therefore, we examined this gene-nutrient interaction in a representative sample of Singaporeans (1324 Chinese, 471 Malays and 375 Asian Indians) whose dietary fat intake was recorded by a validated questionnaire. When no stratification by fat intake was considered, the T allele was associated with higher plasma HDL-C concentrations (P = 0.001), higher triglyceride (TG) concentrations (P = 0.001) and higher HDL-C/TG ratios (P = 0.041). We found a highly significant interaction (P = 0.001) between polymorphism and fat intake in determining TG concentration and the HDL-C/TG ratio (P = 0.001) in the overall sample even after adjustment for potential confounders. Thus, TT subjects showed higher TG concentrations only when fat intake supplied >30% of total energy. This interaction was also found when fat intake was considered as continuous (P = 0.035). Moreover, in the upper tertile of fat intake, TT subjects had 45% more TG than CC individuals (P < 0.01). For HDL-C concentration, the gene-diet interaction was significant (P = 0.015) only in subjects of Indian origin. In conclusion, our results indicate that there are differences in the association of -514C>T polymorphism with plasma lipids according to dietary intake and ethnic background. Specifically, the TT genotype is associated with a more atherogenic lipid profile when subjects consume diets with a fat content > 30%.

Is a re-evaluation of WHO body mass index cut-off values needed? The case of Asians in Singapore.

This paper describes body composition and dietary intakes of the three major ethnic groups residing in Singapore and how these are related to cardiovascular risk factors in these groups. When the relationship between body mass index (BMI, kg/m2) and body fat percentage was studied, Singaporeans were found to have higher percentage of body fat compared with Caucasians with the same BMI. At BMIs that are much lower than WHO-recommended cut-off values for obesity, both the absolute and relative risks of developing cardiovascular risk factors are markedly elevated for all three ethnic groups. The excessive fat accumulation and increased risks at lower BMIs signal a need to re-examine cut-off values for obesity among Chinese, Malays, and Indians.

Validity of body composition methods across ethnic population groups.

Body composition methods can be classified into direct, indirect and doubly indirect methods. In vivo direct methods use neutron activation analysis to get information on body composition. Indirect methods rely on rules and constants derived from direct methods. Most basic research, especially the development of rules and models has been done in Caucasian subjects in Europe or USA. The critical use of more advanced body composition methodologies in various ethnic groups has shown that assumptions may differ between ethnic groups, an example being the assumption of constant density of the fat free mass. Indirect or predictive methods rely on statistical relationships between body parameters and components of body composition. Subcutaneous fat patterning differs among ethnic groups, and this may have consequences for the validity of body fat predicted from skinfold thickness. Relative leg length and relative arm length also differ between ethnic groups. As a result the body mass index (weight/height squared, BMI), often used as surrogate for body fat percent, and formulas based on bioelectrical impedance measurement show different validity among ethnic groups. Less information is available about the validity of indicators for body fat distribution. There are indications that the relationship between the amount of visceral adipose tissue and waist circumference or waist-hip circumference ratio also differs among ethnic groups. Ethnic differences in body composition rules and constants are important and challenging to investigate, especially in relation to overweight and obesity.

Validity of deuterium oxide dilution for the measurement of body fat among Singaporeans.

Body fat percent (BF%) was measured in 108 adult Chinese, 76 Malays, and 107 Indians in Singapore by densitometry, deuterium oxide dilution (hydrometry), dual energy x-ray absorptiometry (DXA) and a chemical four-compartment model (BF%4c). The hydration of the fat-free mass (FFM) was calculated. Subjects ranged in age from 18 to 69 years and their body mass index ranged from 16 to 40 kg/m2. BF%4c for the various subgroups were: Chinese females (33.5 +/- 7.5%), Chinese males (24.4 +/- 6.1%), Malay females (37.8 +/- 6.3%), Malay males (26.0 +/- 7.6%), Indian females (38.2 +/- 7.0%) and Indian males (28.1 +/- 5.5%). Biases were found between BF%4c and BF% measured by 2-compartment models (hydrometry, densitometry, DXA), with systematic underestimation by DXA and densitometry. On a group level hydrometry had the lowest bias while DXA gave the highest bias. When validated against BF%4c, 2-compartment models were found to be unsuitable for accurate measures of body fat due to high biases at the individual level and the violation of assumptions of constant hydration of FFM and density FFM among the ethnic groups. On a group level the best 2-compartment model for measuring body fat was found to be hydrometry.

Validation of skinfold thickness and hand-held impedance measurements for estimation of body fat percentage among Singaporean Chinese, Malay and Indian subjects.

Body fat percentage (BF%) was measured in 298 Singaporean Chinese, Malay and Indian men and women using a chemical four-compartment model consisting of fat, water, protein and mineral (BF%4C). In addition, weight, height, skinfold thickness and segmental impedance (from hand to hand) was measured. Body fat percentage was predicted using prediction equations from the literature (for skinfolds BF%SKFD) and using the manufacturer's software for the hand-held impedance analyser (BF%IMP). The subjects ranged in age from 18-70 years and in body mass index from 16.0 to 40.2 kg/m2. Body fat ranged from 6.5 to 53.3%. The biases for skinfold prediction (BF%4C-BF%SKFD, mean +/- SD) were -0.4+/-3.9, 2.3+/-4.1 and 3.1+/-4.2 in Chinese, Malay and Indian women, respectively, the Chinese being different from the Malays and Indians. The differences were significant from zero (P < 0.05) in the Malays and Indians. For the men, the biases were 0.5+/-3.8, 0.0+/-4.8 and 0.9+/-4.0 in Chinese, Malays and Indians, respectively. These biases were not significantly different from zero and not different among the ethnic groups. The biases for hand-held impedance BF% were -0.7+/-4.5, 1.5+/-4.4 and 0.4+/-3.8 in Chinese, Malay and Indian women. These biases were not significantly different from zero but the bias in the Chinese was significantly different from the biases in the Malays and Indians. In the Chinese, Malay and Indian men, the biases of BF%IMP were 0.7+/-4.6, 1.9+/-4.8 and 2.0+/-4.4, respectively. These biases in Malay and Indian men were significantly different from zero and significantly different from the bias in Chinese men. The biases were correlated with level of body fat and age, and also with relative arm span (arm span/height) for impedance. After correction, the differences in bias among the ethnic groups disappeared. The study shows that the biases in predicted BF% differ between ethnic groups, differences that can be explained by differences in body composition and differences in body build. This information is important and should be taken into account when comparing body composition across ethnic groups using predictive methods.