Validity of the body mass index as an indicator of adiposity in an ethnically diverse population of youths

New Equations to Predict Body Fat in Asian-Chinese Adults Using Age, Height, Skinfold Thickness, and Waist Circumference

BACKGROUND

Adiposity is an independent predictor of metabolic disease. However, highly accurate body fat assessment is not routinely done due to limited access to expensive and labor-intensive methods.

OBJECTIVE

The aim of the study was to develop body fat prediction equations for Asian-Chinese adults using easily attainable anthropometric measurements.

DESIGN

Prediction equations of body fat were developed using anthropometric and skinfold thickness measurements obtained from a cross-sectional study. These new equations were then validated using baseline data from an independent randomized controlled study.

PARTICIPANTS/SETTING

Healthy participants with no major diseases and not taking long-term medications were recruited in an ongoing cross-sectional study that began in June 2014 (n=439, 170 males, 269 females), as well as a randomized controlled trial (n=108, 58 males, 50 females) conducted from January 2013 to October 2014. Both the studies were conducted at Clinical Nutrition Research Center located in Singapore.

MAIN OUTCOME MEASURES

Data used to develop and validate equations were from two original studies that assessed body fat by dual-energy x-ray absorptiometry, age, waist circumference, height, and biceps and triceps skinfolds.

STATISTICAL ANALYSIS PERFORMED

Sex-specific percent body fat prediction equations were developed using stepwise regression with Akaike Information Criterion on the cross-sectional data. The equations were then validated using data from the randomized controlled study and also compared against Asian-specific Davidson equations.

RESULTS

The best body fat prediction model (R²=0.722, standard error of estimation=2.97 for females; R²=0.815, standard error of estimation=2.49 for males) for both sexes included biceps and triceps skinfolds, waist circumference, age, and height. The new equations developed resulted in modest discrepancies in body fat of 1.8%±2.7% in males (P<0.001) and 0.7%±3.1% in females (P=0.125; not significant) compared with the Asian-specific Davidson equations (-7.4%±3.2% [P<0.001] and -7.4%±2.7% [P<0.001], respectively).

CONCLUSIONS

Sex-specific equations to predict the percent body fat of Asian-Chinese adults with a higher degree of accuracy were developed. Ease of use in both field and clinical settings will be a major advantage.

Musculoskeletal stress marker (MSM) differences in the modern American upper limb and pectoral girdle in relation to activity level and body mass index (BMI)

Obesity is a widespread condition affecting modern Americans. The prevalence of obesity has led to questions of how it can affect the skeleton, and if so can it be identified in unknown skeletal material. This study attempts to decipher the effects of activity level and body mass in modern Americans by employing musculoskeletal stress markers (MSM) to estimate osseous responses to workload and body weight. A total sample of 108 skeletons of known activity level and body mass index (BMI) was observed for MSM in the upper extremity (excluding hands). The entheses selected included arm muscles used during the sit-to-stand transition, which is common in most persons, regardless of activity level and BMI. Using the three categories: normal, active, and obese, logistic regression was calculated on MSM to ascertain which markers were the best indicators of these three categories. Numerous muscles of the upper limb were significant predictors of activity level and body mass, although they did not perform much better than chance. MSM may be used as predictors of activity level and/or BMI in forensic contexts; however, they should be used in conjunction with other indications of workload and/or BMI.

Ethnic differences in the relationship between body mass index and percentage body fat among Asian children from different backgrounds

Overweight and obesity in Asian children are increasing at an alarming rate; therefore a better understanding of the relationship between BMI and percentage body fat (%BF) in this population is important. A total of 1039 children aged 8-10 years, encompassing a wide BMI range, were recruited from China, Lebanon, Malaysia, The Philippines and Thailand. Body composition was determined using the 2H dilution technique to quantify total body water and subsequently fat mass, fat-free mass and %BF. Ethnic differences in the BMI-%BF relationship were found; for example, %BF in Filipino boys was approximately 2 % lower than in their Thai and Malay counterparts. In contrast, Thai girls had approximately 2.0 % higher %BF values than in their Chinese, Lebanese, Filipino and Malay counterparts at a given BMI. However, the ethnic difference in the BMI-%BF relationship varied by BMI. Compared with Caucasian children of the same age, Asian children had 3-6 units lower BMI at a given %BF. Approximately one-third of the obese Asian children (%BF above 25 % for boys and above 30 % for girls) in the study were not identified using the WHO classification and more than half using the International Obesity Task Force classification. Use of the Chinese classification increased the sensitivity. Results confirmed the necessity to consider ethnic differences in body composition when developing BMI cut-points and other obesity criteria in Asian children.

Methodological issues in the anthropometric assessment of Hmong children in the United States

The effectiveness of the body mass index (BMI; kg/m2) in assessing overweight/obesity may be diminished in populations of short stature. In a sample (n = 79) of Hmong refugee children in the United States, of age 4-11 years, median z scores for height, BMI, and the triceps skinfold were -1.04z, +0.53z, and +0.18z, respectively. Further, 41.7% of children were above the NHANES 85th percentile for BMI-for-age, categorizing them as overweight/obese. Assessment of obesity by other established criteria for children, such as the triceps skinfold and body fat percentage, produced significantly lower estimates than did BMI. This is consistent with patterns found in other stunted populations, suggesting that BMI be employed in conjunction with other methods when assessing overweight/obesity in these groups. Finally, although stunting and overweight/obesity were both common in this study, at the individual level height z scores were positively correlated to z scores of various measures of adiposity.

Adiposity, central body fat distribution and blood pressure among young Bengalee adults of Kolkata, India: sexual dimorphism

A cross-sectional study of 174 men and 153 women of Bengalee ethnicity was undertaken to compare levels of adiposity, central body fat distribution and blood pressure. The mean age of both the sexes were similar (men = 20.1 years; women = 20.0 years). Significantly more women (n = 42, 27.5%) were overweight (body mass index, BMI > or = 25.0 kg/m2) as compared with men (19, 10.9%). Men were significantly taller and heavier. They also had significantly greater mean waist (WC) and mid upper arm (MUAC) circumferences compared with women. On the other hand, women had significantly (p < 0.001) greater mean BMI, biceps (BSF), triceps (TSF) and subscapular (SSF) skinfolds. The mean values of systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure were significantly greater among men. These significant differences existed even after controlling for BMI. Regression analyses revealed that sex had significant effect on all these variables even after controlling for BMI. Correlation studies showed that WC was found to be much more strongly correlated than BMI with SBP, DBP and MAP, in both sexes. However, when the effect of WC (along with BMI) was also controlled for, there was no significant sex difference in blood pressure.

Relationship of body composition to body-fatness estimation in Japanese university students

OBJECTIVE

To examine the relationship between self-estimated whole body size and fatness and whole body and regional composition, and the relationship between self-estimated whole body fatness and self-estimated regional fatness in Japanese university students.

RESEARCH METHODS AND PROCEDURES

This was a cross-sectional study using Japanese university students (110 men and 79 women). The percentage of body fat, fat mass (FM), and fat-free mass (FFM) were measured by underwater weighing and used as body composition variables. Subcutaneous fat thicknesses were determined at seven sites by ultrasonography to estimate regional body composition, and six circumferences and four breadths to estimate regional size. Relative body size and fatness were self-estimated using a questionnaire.

RESULTS

Only women tended to estimate themselves as being fatter than they actually were. Self-estimated body fatness moderately correlated with the percentage of body fat (men, r = 0.41; women, r = 0.40) FM (men, r = 0.50; women, r = 0.51), and body mass index (r = 0.56 for men and 0.56 for women). After adjusting for the percentages of body fat and FM, self-estimated fatness correlated with body mass index (r = 0.31 for men and r = 0.37 for women). Among self-estimated regional fatness, self-estimated abdominal fatness had the strongest correlation with self-estimated whole body fatness in both genders.

DISCUSSION

The low correlation between estimated and actual body fatness in both genders indicates that Japanese university students, especially women, inaccurately estimate their percentage of body fat. In fact, both men and women primarily estimate their whole body fatness by body weight relative to height.

Anthropometric changes in urban Sardinian children 7 to 10 years between 1975-1976 and 1996

This study is a comparison of several anthropometric variables in school children of the same age (7-10 years) and sex measured in two primary schools in Cagliari (Sardinia, Italy) at an interval of 20 years (1996 vs. 1975-1976). For both males and females of each age-class, there are significant differences in the following dimensions: weight, stature, estimated lower limb length, biacromial breadth, xiphoid chest circumference, xiphoid chest depth, and bicristal breadth, and also in relative sitting height, cephalic index, and facial index. The means of the relative sitting height, cephalic, and facial indexes are higher in the children measured in 1975-1976 than in those measured in 1996. There are no significant differences in sitting height and arm length. In addition, the estimated BMIs of the 1975-1976 sample are, on average, lower than those of the 1996 sample. The results suggest that urban Sardinian children sampled in 1996 are generally taller, heavier, and larger and have a longer head and wider face than their peers of 20 years earlier. The increase in stature is due more to an increase in lower limb length than in sitting height. Am J. Hum. Biol. 12:782-791, 2000. Copyright 2000 Wiley-Liss, Inc.

Lifetime dietary change and its relation to increase in weight in Spanish women

INTRODUCTION

Changes in dietary patterns and a decrease in physical activity have occurred in Western countries. These are factors in the variation in body composition observed in populations, characterized by a progressive accumulation of fat with age and a consequent increase in the risk of suffering from common chronic illnesses such as obesity, cardiovascular disease and cancer.

OBJECTIVE

To investigate weight gain throughout the life-cycle and its relation to modifications in dietary patterns, analyzing the causes of these modifications and their implications for patterns of adult overweight and obesity.

DESIGN

Cross-sectional sample of Spanish women from a socio-economically disadvantaged class.

SUBJECTS

1037 healthy perimenopausal women (age: 45-65 y).

MEASUREMENTS

Juvenile body mass index (BMI), current BMI, food frequency questionnaire, retrospective food habits.

RESULTS AND CONCLUSIONS

Of these women, 48.8% had changed their dietary habits during their lifetime. A change in diet due to migration or marriage occurred at approximately 20 years of age and was characterized by an increased frequency of consumption of foods rich in protein and complex carbohydrates, while a change due to illness occurred at around 50 years of age and was characterized by a decrease in the consumption of these types of food. The change in dietary behavior due to migration was associated with weight gain. Weight gain was also inversely associated with BMI during youth; women who in their youth had a BMI<18.5 kg/m2 gained an average of 21.4 kg, compared with those with a BMI>27 kg/m2 in their youth, who gained an average of 5.4 kg. International Journal of Obesity (2000)24, 14-19