Objective: To compare the distributions of body mass index (BMI) in relatively healthy nonsmoking men and women in the United States.
Design: Cross-sectional national survey data from the Third National Health and Nutrition Examination Survey (NHANES III).
Subjects: I n total, 11,404 nonsmoking men (n = 4894) and women (n = 6510), ages 20 years and above, drawn from a representative population sample.
Measurements: Increasingly stringent definitions of 'health' were applied, based on self-reported health, medical history, measurements of blood pressure, blood lipids, serum glucose, glycosylated hemoglobin, and behavioral factors including smoking and physical activity. Main outcome measures were mean and median BMI by health level, 5th and 95th percentiles of BMI, and the prevalence of overweight and obesity.
Results: For both men and women, the distribution of BMI became less skewed at better health levels. The range of BMI values that included 90% of healthy men and women was approximately 19.5-30 kg/m2 for men and 18-30 kg/m2 for women, with median values of approximately 24.5 kg/m2 for men and 21.5 kg/m2 for women. The prevalence of overweight declined sharply with increasing health level for women but varied little for men; the prevalence of obesity declined at higher health levels for both men and women.
Conclusions: Only about 5% of healthy younger men or women would be classified as obese by BMI levels. However, the distribution of BMI differs between healthy men and healthy women. Relative to the distribution of BMI values for healthy men, the distribution of BMI values for healthy women is shifted to the left and is more skewed.