By Lee Bowman
Scripps Howard News Service
March 18, 2005
The circumference of the waist appears to be a better predictor of disease than calculating body fat using weight-to-height or waist-to-hip ratios, researchers have found.
Everyone pretty much agrees that having a body mass index (weight-to-height ratio) of 25 or less is desirable _ that's the cutoff for being overweight; 30 and higher is considered obese. BMI for a 6-foot tall man exceeds 25 if he weighs more than 190 pounds; for a 5-foot-4 woman, if she exceeds 150 pounds.
Guidance has been less sure for waist size, even though it's a simple tape measurement to establish. Most experts have been advising that waist size greater than 40 inches for men and 38 in women is reason for concern. But the new research pares this down.
In general, health experts have found that more fat stored around the abdomen _ an apple shape _ is more dangerous than carrying fat around the hips and thighs, the pear shape.
Back-to-back studies in the February and March issues of the American Journal of Clinical Nutrition document the waistline as a window to health status. The first, done by researchers from the Medical College of Wisconsin and the New York Obesity Research Center at Columbia University, looked at waist circumference of more than 10,000 people who took part in a government survey of health data between 1988 and 1994.
They found better correlation between waist size and cholesterol, blood pressure and blood glucose levels than BMI in both men and women, including blacks, Hispanics and whites, largely independent of age.
Using those results, the researchers conclude that in all three racial-ethnic groups, the overweight BMI of 25 corresponds to a waist size greater than 35 inches in men and 33 inches in women; the obese BMI of 30 matches a waist of 39.8 inches for men, 37 inches for women.
The most recent study, led by Youfa Wang, an assistant professor at the Johns Hopkins Bloomberg School of Public Health, looked only at men's waist sizes relative to diabetes risk, but also found that risk started to creep up when the belt size went higher than 35 inches, and that 80 percent of type 2 diabetes cases occurred in men with waists larger than 37 inches.
"Both BMI and waist circumference are useful tools to assess health risk," said Wang. "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.
"Many of the men who developed type 2 diabetes had measurements lower than the current (40 inch) cutoff."
The study was based on data collected from 27,270 men tracked over 13 years through the Harvard Health Professionals Follow-Up Study.
Men who had a waist size of 40 inches or more were 12 times more likely to develop the type of diabetes in which the pancreas either doesn't make enough insulin or doesn't respond properly to insulin than men with waist sizes of 34 or less.
With a waist size of 34 to 36, the diabetes risk doubled; at 36 to 38 inches, the risk tripled; and at 38 to 40 inches, the risk for the disease was five times greater.
So, in addition to measuring BMI, the researchers recommend that doctors measure waist size as an indicator of central obesity to estimate diabetes risk for patients and make decisions with them about changes in diet and lifestyle.
On the Net: www.ajcn.org
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