Having a big waist may raise women's death rates, even in women who aren't overweight. The results of a recent study of 44,600 female nurses who were enrolled in a long-term health study showed that large waists were worse for you than being overweight. 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 reported in the April 1 edition of Circulation.

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.

The nurses health was accuratly tracked for 16 years. During the time of the study, a total of 3,507 of the nurses died, including 751 who died of heart disease and 1,748 who died of cancer. 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 your waist is all that's needed. The researchers found that waist-to-hip ratio was a worse predictor of death rates and was more effort.

Cuilin Zhang, MD, PhD, of the National Institute of Child Health and Human Development used the definitions for abdominal obesity recommended by the American Heart Association and U.S. Department of Agriculture. Those ranges are waist circumference of 34.6 inches for women and 40 inches for men.

The study doesn't definately prove that abdominal fat is lethal. Observational studies like this one don't prove cause and effect.