Premenopausal women who make even small increases in the amount of time they spend bicycling or walking briskly every day decrease their risk of gaining weight, according to a new study by researchers from the Harvard School of Public Health (HSPH), Boston.

The study appears in the June 28, 2010 issue of the journal Archives of Internal Medicine.

For premenopausal women of any weight, riding a bicycle was effective in helping to maintain weight, and overweight and obese women appeared to benefit the most. The researchers found that among women who did not originally bicycle in 1989 but bicycled in 2005, even a small increase in bicycling time–as little as five minutes each day–helped to control weight. Among the walkers who had increased their daily activity by an average of 30 minutes/day over the years, only those who walked briskly (≥3 mph) were able to control their weight. Walking slowly (<3 mph) had no effect.

The results come from an examination of 18,414 premenopausal women, free from chronic diseases such as diabetes, cancer, or cardiovascular disease, participating in the Brigham and Women’s Hospital-based Nurses’ Health Study II. This is an ongoing study in which participants respond to a questionnaire about their medical history, lifestyle and health-related behaviors every 2 years. In 1989 and 2005, participants reported on time spent engaging the previous year in various recreational activities.

Study results showed that women in the study gained an average of 9.3 kilograms (20.5 pounds) over the 16-year period. Even though women gain weight as they age, normal-weight women who were bicycling more than four hours a week in 2005, irrespective of their physical activity level in 1989, were 26% times less likely to gain more than five percent of their initial body weight. Overweight and obese women who were bicycling just two or three hours a week were 56% times less likely to gain weight.

According to the authors, it is the first study to look at the relationship between bicycling and weight control among women.

"This study shows that more bicycling predicts less weight gain," said Rania Mekary, research associate in the HSPH Department of Nutrition.

"Small daily increments in bicycling helped women control their weight. But the more time women spent bicycling, the better. Women with excess weight appeared to benefit the most. This is encouraging for women with weight problems because they could substitute bicycling for slow walking or car driving," said Mekary.

In the United States, 66% of adults are overweight or obese, 16% of children and adolescents are overweight, and 34% of children and adolescents are at risk of becoming overweight. The Centers for Disease Control and Prevention and the American College of Sports Medicine recommend that every adult accumulate 30 minutes or more of moderate-intensity activity on most, preferably all, days of the week to prevent obesity and improve health.

"Our study provides evidence that to combat obesity, the US needs to have policies that not only endorse design guidelines for sidewalks, but also for separate and comfortable places to bicycle, such as cycle tracks between sidewalks and parked cars," said Anne Lusk, research fellow in the HSPH Department of Nutrition.

When promoting physical activity to their patients, the authors encourage physicians to prescribe brisk walking, rather than just walking, but also bicycling. "Bicycling may be more comfortable than brisk walking, especially for overweight women," said Lusk.

"Bicycle Riding, Walking, and Weight Gain in Premenopausal Women," Anne C. Lusk, Rania A. Mekary, Diane Feskanich, Walter C. Willett, Archives of Internal Medicine, June 28, 2010, vol. 170, no. 12.

[Source: Eureka Alert on behalf of Harvard School of Public Health]