Bicycling may help women control their weight during their 30s and 40s, a new study says. Brisk walking has the same effect for slim, overweight and obese women, researchers found, but slow walking does not.

The findings are based on the second Harvard Nurses’ Health Study, which is tracking 116,608 female nurses who periodically fill out questionnaires about their health, weight, diet and behavior. The new analysis, published in the June 28 issue of Archives of Internal Medicine, looked at weight change and behavior from 1989 (when the nurses were 25 to 42 years old) to 2005; to isolate the effects of exercise, the researchers controlled for other obesity risk factors.

They found that women who increased physical activities like brisk walking and bicycling by 30 minutes a day during the 16-year period maintained their weight and even lost a few kilograms, but those whose exercise was slow walking did not lose any weight.

Women who decreased their bicycling time from more than 15 minutes a day to less than 15 gained about 2 kilograms on average.

“This is not suggesting that if you bicycle for five minutes you will immediately go back to the weight you were when you were 18,” said Anne C. Lusk, a research fellow at the Harvard School of Public Health who was an author of the paper. “But it’s highly suggestive that bicycling is highly beneficial in women.”

RONI CARYN RABIN