Body mass index as an indicator of adiposity among adults with intellectual disability

Background Body mass index (BMI) has been identified as a key health indicator and determinant of health for people with intellectual disability. Our aim was to examine whether BMI is a useful indicator of adiposity among a sample of adults with intellectual disability. Method Participants were 46 ambulatory community-dwelling volunteers with mild to moderate intellectual disability. Age ranged from 19 to 60 years, 25 were male, and 17 had Down syndrome. Soft tissue composition was determined using a dual-energy X-ray absorptiometer (DXA) and height and weight were directly assessed. Results Regression equations revealed that BMI accounted for 68% of the variance in percent body fat and 83% of the variance in total body fat. Partial correlations of BMI with fat and lean masses determined by DXA were r = .91 and r = −.12, respectively. A BMI of ≥ 30 had excellent specificity for obesity, but less than optimal sensitivity. Conclusions BMI appears to be a reasonable indicator of adiposity, although a BMI ≥ 30 may misclassify a proportion of individuals assessed by DXA as obese.