Being fit but fat isn't good enough. Excess weight, all by itself, can take years off your life, even if you get plenty of exercise, a study found.

"There has been some suggestion that if you are particularly active, you don't have to worry about your body weight, about your diet. That's very misleading," said the report's lead author, Dr. Frank Hu of the Harvard School of Public Health.

The study of 116,500 women was published in the New England Journal of Medicine and was based on questionnaires used in the Nurses' Health Study, which has followed female nurses since 1976, and on death certificates and medical records.

Women who were physically active but obese had almost twice the risk of death of women were both active and lean. Women who were sedentary but slender were 55 percent more likely to die early. Women who were both sedentary and obese were almost 2 1/2 times more likely to die.

"Being physically active did not cancel out the increased mortality of overweight. Being lean did not counterbalance the risk effect of being sedentary," Hu said.

Exercise and diet are equally important in maintaining long-term health, and subjects of this study are a clear indication of that.

An editorial by David R. Jacobs Jr. and Mark A. Pereira of the University of Minnesota noted that the study relied on nurses' reports of exercise and weight rather than direct measurement, and did not include light to moderate exercise — the form most Americans get.

Dr. Timothy Church of the Cooper Institute, which is devoted to research on exercise and health, praised the findings. "If you're lean but you're sedentary, don't fool yourself. You're still at risk. You need to get physically active," he said.

A separate study in the journal — the longest look yet at the effects of stomach-stapling and other obesity surgery — found that the weight loss and the protection against diabetes that result are major and long-lasting.

The Swedish study, led by Dr. Lars Sjostrom of Sahlgrenska University Hospital in Goteborg, looked at more than 4,000 people, about half of whom underwent surgery. The other half were advised to change their habits, or got no treatment at all.

Two years later, the surgery group had lost about 23 percent of its original weight, while those in the comparison group weighed almost exactly the same. Ten years later, the comparison group had gained an average of 1.6 percent. Those who underwent surgery had regained a larger percentage — but were still 16 percent below their original weights.

Many surgical patients recovered from diabetes, and the operation prevented many new cases. Their levels of fats called triglycerides were lower, and their levels of "good" cholesterol were higher.

But trends toward lower blood pressure and lower overall cholesterol levels among the surgery patients were not big enough to count as real differences.

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