April 8, 2008 -- Having a big waist may raise women's death rates, even in women who aren't overweight.
That news comes from a study of 44,600 female nurses enrolled in a long-term health study.
The bottom line: Waists mattered more than weight.
Being in the normal weight range was less important than having a waist less than 34.6 inches and a waist-to-hip ratio of less than 0.88 .To calculate your waist-to-hip ratio, divide your waist measurement by your hip measurement.
"Although maintaining a healthy weight should continue to be a cornerstone in the prevention of chronic diseases and premature death, it is equally important to maintain a healthy waist size and prevent abdominal obesity," the researchers write in the April 1 edition of Circulation.
Belly Fat Study
When the nurses were 40 to 65 years old, they measured their waists and hips for the study. At the time, none had had heart disease or cancer.
Every two years, they updated their health and lifestyle records for the study, including their physical activity, smoking, alcohol use, and menopausal status.
Regardless of other factors, including BMI (body mass index, which relates height to weight), women with larger waists and greater waist-to-hip ratios had higher death rates from all causes, including heart disease and cancer, which are the top two killers of U.S. women.
For example, among women of normal weight, those with a waist larger than 34.6 inches were three times as likely to die of heart disease, compared to women with smaller waists.
Large hips weren't a problem, if the waist wasn't also large. In fact, having large hips and a small waist was associated with lower risk of death from heart disease.
Simply measuring the waist will do. The waist-to-hip ratio wasn't a better predictor of death rates and is more cumbersome, note the researchers, who included Cuilin Zhang, MD, PhD, of the National Institute of Child Health and Human Development.
Zhang's team used the definitions for abdominal obesity recommended by the American Heart Association and U.S. Department of Agriculture. Those cutoffs are waist circumference of 34.6 inches for women and 40 inches for men.
The study doesn't prove that abdominal fat is lethal. Observational studies like this one don't prove cause and effect.