International Journey of Obesity (2005) 0, 000-000
Obesity is a major risk factor for diabetes and related disorders. The current classification of obesity is based on body mass index (BMI, kg/m2), which is a surrogate for the total body fat. Since the relationship between BMI and body fat varies in different populations, an independent validation of the BMI-body fat relationship in the population of interest is desirable.
OBJECTIVES: (1) To study the validity of field methods of measuring body fat (multiple skinfolds and bioimpedance) against a criterion method (deuterium dilution) and (2) To compare the prevalence of obesity (WHO 2000 criteria for BMI) with adiposity (body fat > 25%) in middle-aged Indian men in rural and urban Pune.
DESIGN: Community-based multistage stratified random sampling of middle-aged men from rural and urban Pune for study of body composition and cardiovascular risk. A third of these men, selected to represent wide BMI distribution, were studied for body fat measurements by specific methods.
SUBJECTS: A total of 141 healthy men, approximately similar number from rural, urban slums and middle class from Pune. They were 39.3 (±6.2) y old and had a BMI of 21.9 (±3.7) kg/m2.
MEASUREMENTS: Anthropometry (height, weight and multiple skinfold thicknesses) by trained observers using standardized technique to calculate body fat by Durnin and Womersley’s equation. Total body water and body fat by bioelectrical impedance analysis (BIA) Bodystat® MultiScan 5000 and deuterium dilution (D2O).
RESULTS: Mean total body fat was 14.3 kg (23.0%) by anthropometry, 16.5 kg (26.0%) by BIA and 15.3 kg (24.6%) by D2O method. Although there was a good correlation between fat estimation by three methods (r = ~0.9, P<0.001 all), compared to D2O method anthropometry underestimated body fat by 1.0 kg and BIA overestimated fat by 1.2 kg (P<0.001 both). Using the standard cut-point of 25% body fat for ‘adiposity’ 29.5% rural, 46% slum and 75.0% middle class men were adipose. These proportions were considerably higher than the number of men who were ‘preobese’ (BMI≥25-29.9 kg/m2, 9.0% rural, 22.0% urban slums and 27.0% urban middle class) and ‘obese’ (BMI>30 kg/m2, 4.0% urban slums, none in rural and urban middle class).
CONCLUSION: We recommend that future studies assessing risk for chronic diseases in Indians should measure adiposity by anthropometry (multiple skinfolds) or BIA (calibrated for Indians) rather than relying only on BMI cut-points.