Whether higher levels of physical activity can counteract the detrimental effects of carrying too much weight "is controversial," Dr. Frank B. Hu, from the Harvard School of Public Health in Boston, and his colleagues explain in this week's New England Journal of Medicine.

They analyzed data from 116,564 women enrolled in the Nurses' Health Study who, at the beginning of the study in 1976, were between the ages of 30 to 55 and were free of cardiovascular disease.

During 24 years of follow-up, 10,282 women died -- 2370 from cardiovascular disease, 5223 from cancer and 2689 from other causes.

"Contrary to some assertions, a high level of physical activity did not eliminate the risk of premature death associated with obesity," Hu told Reuters Health. "On the other hand, leanness did not cancel out the increased mortality due to inactivity."

Hu noted that "there was nearly a two and a half-fold increase in risk of death for inactive and obese women" compared to physically active, lean women.

Summing up, Hu said this study shows that "both weight and exercise are important for longevity."

The authors of a commentary in the journal say that this study has a "basic and helpful conclusion in terms of public health: be fit and lean if you can be."

SOURCE: New England Journal of Medicine, December 23, 2004.