Activity alone can’t overcome obesity’s risks

Regular exercise is not enough to offset the health problems associated with obesity -- but that shouldn’t stop people who are overweight from working out, researchers say.

Two-thirds of Americans are classified as overweight or obese. Being obese triples the risk of heart disease and produces a tenfold increase in the likelihood of developing diabetes.

In recent years, some doctors have suggested that getting regular exercise could eliminate much of the risk of being fat.

But a study in the Dec. 23 issue of the New England Journal of Medicine, which followed more than 116,000 female nurses for 24 years, challenges that belief.

Frank Hu of the Harvard School of Public Health and his colleagues found that a high level of physical activity did not eliminate the risk of premature death associated with obesity -- and leanness did not offset the increased risk in mortality conferred by inactivity.

Lean women who exercised less than 3 1/2 hours per week increased their risk of early death by 55% compared with women who worked out more frequently, the researchers found.

Among obese women who worked out for at least 3 1/2 hours weekly, the death rate was 91% higher than in lean women who exercised for 3 1/2 hours weekly.

And for inactive, obese women, the premature death rate was 142% greater.