Body Mass Index, Waist Circumference, and Health Risk

Abstract

IN 1998, the National Heart, Lung, and Blood Institute of the National Institutes of Health (NIH) published evidence-based clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults.¹ These guidelines included a classification system for assessing health risk based on the body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) and waist circumference (WC). In this classification system, a patient is placed in 1 of 6 BMI categories (underweight, normal-weight, overweight, or class I, II, or III obese) and 1 of 2 WC categories (normal or high). The relative health risk is then graded on the basis of the combined BMI and WC. The health risk increases in a graded fashion when moving from the normal-weight through class III obese BMI categories,^2,3 and it is assumed that within the normal-weight, overweight, and class I obese BMI categories, patients with high WC values have a greater health risk than patients with normal WC values. This classification system was developed on the basis of the knowledge that an increase in BMI is associated with an increase in health risk, that abdominal or android obesity is a greater risk factor than lower-body or gynoid obesity, and that the WC is an index of abdominal fat content.¹