The findings are based on data collected from 27,270 men tracked over 13 years who participated in the Harvard Health Professionals Follow-Up Study.
Men who had larger waists assessed using waist circumference and waist-hip ratio or higher overall body fat indicated by BMI had a greater risk of developing type 2 diabetes.
The researchers grouped the study participants into five groups according to their waist size. Compared to those in the group with the smallest waists, the others were up to twelve times more likely to develop diabetes, respectively. Similarly, risk was up to seven times greater when waist-hip ratio was measured in men; and eight times greater when BMI was measured.
"Both BMI and waist circumference are useful tools to assess health risk," said the study's lead author, Youfa Wang, PhD, MD, assistant professor with the Center for Human Nutrition at Johns Hopkins. "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 authors suggest that the currently recommended waist circumference cutoff of 40 inches for men may need to be lowered. "Many of the men who developed type 2 diabetes had measurements lower than the cutoff," explains Wang, "and the risk associated with waist circumference increased at a much lower level."
While nearly 80 percent of the men in this cohort who developed type 2 diabetes could be identified using a BMI of 25 - the cutoff for overweight - only half had a waist circumference greater than or equal to 40 inches - the cutoff recommended by the National Institutes of Health.
The study authors also urge that more research on this topic be conducted with cohorts that include women and different ethnic and racial groups, since the Health Professionals Follow-Up Study only followed a cohort of largely white, professional men who are likely to be healthier than the average American.
MEDICA.de; Source: Johns Hopkins University Bloomberg School of Public Health