Fitness and Fatness: Body Mass Index versus Percent Body Fat

Abstract

ABSTRACT Background: Body mass index (BMI) is frequently used to evaluate risk of disease, but can be misleading because it does not account for different types of tissue mass (e.g., bone, muscle, fat). The purpose of this study was to classify adults in the United States according to cardiovascular fitness (CVF), BMI, and body fat using the National Health and Nutrition Examination Survey (NHANES) data. Methods: The three most current NHANES datasets (6,648 records) were included. Counts, means, and 95% confidence intervals (CI) determined the distribution of CVF across percent of body fat and BMI categories. Results: According to BMI, approximately 42.3% of participants were classified as either underweight or normal weight, and 24.9% were classified as obese. According to percent of body fat, 13.5% of subjects were classified as lean, while 68.4% of subjects were in the high percent body fat group. In regard to BMI, 9.9% and 6.7% of the overweight and obese populations, respectively, were classified in the highest third of CVF. According to adiposity, 6.6% and 21.0% of the moderate and high percent body fat population fell into the same category, respectively. Conclusion: Two-thirds of the population ranked below the 35th percentile for body fat (high percent body fat), with more of these individuals in the low CVF category than any other. The largest categorization for BMI was the normal-weight category. This supports that BMI may be misleading, and that utilizing percent body fat and CVF may provide a better indication of health.