A study by Youfa Wang, PhD, MD, assistant professor with the Centre for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health, published in the current issue of the American Journal of Clinical Nutrition, has found that the size of a man's waist is a better predictor of his risk of developing type 2 diabetes than his body mass index (BMI).
Based on data collected from 27,270 men tracked over 13 years who participated in the Harvard Health Professionals Follow-Up Study, it was found that men who had larger waists or higher overall body fat had a greater risk of developing type 2 diabetes.
The men were placed into five groups according to their waist size. Compared to those in the group with the smallest waists (29-34 inches), the other groups (34.-35.9 inches, 36-37.8 inches, 37.9-39.8 inches, 40-62 inches) were 2, 3, 5 and 12 times more likely to develop diabetes, respectively. Similarly, risk was 2, 3, 4 and 7 times greater when waist-hip ratio was measured in men; and 1, 2, 3 and 8 times greater when BMI was measured.
Dr.Wang says that both BMI and waist circumference are useful tools to assess health risk, but abdominal fat measured by waist circumference can indicate a strong risk for diabetes whether or not a man is considered overweight or obese according to his BMI. The research suggests that the currently recommended waist circumference cut-off of 40 inches for men may need to be lowered as many of the men who developed type 2 diabetes had measurements lower than the cut-off.
While nearly 80 percent of the men in this cohort who developed type 2 diabetes could be identified using a BMI of 25 - the cut-off for overweight - only half (50.5 percent) had a waist circumference greater than or equal to 40 inches?the cut-off recommended by the National Institutes of Health.