Just five minutes of riding a bicycle each day can help a younger woman keep the pounds off, U.S. researchers reported on Monday in a study offering one potentially easy way to help Americans slim down.

“Small daily increments in bicycling helped women control their weight. But the more time women spent bicycling, the better,” said Rania Mekary, of the Harvard School of Public Health in Boston, who worked on the study.

“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.”

The research could help public policymakers trying to find ways to slow the U.S. obesity epidemic, the researchers wrote in the Archives of Internal Medicine.

Two-thirds of U.S. adults are overweight or obese and 16 percent of children and adolescents are overweight.

The accompanying disease burden costs billions and President Barack Obama has assigned his wife Michelle Obama and cabinet secretaries to find ways to counter this trend.

Their plan includes changes to neighborhoods and cities to make it easier for Americans to exercise.

Mekary and colleagues studied 18,414 healthy women who had not yet gone through menopause taking part in the Brigham and Women’s Hospital-based Nurses’ Health Study, an ongoing study of women’s health over time.

On average, the nurses gained about 20 pounds (9.3 kilograms) over the 16-year period.

The women who did not bicycle in 1989 who had started by 2005 were a quarter less likely to have gained weight, even if they rode for just five minutes a day, the researchers found.

Comparatively, women who started out exercising on bikes for more than 15 minutes day in 1989 but who slacked off over time gained weight.

Overweight and obese women who were bicycling just two or three hours a week were 56 percent less likely to gain weight.

Brisk walking, but not slower strolling, was also helpful in keeping weight off, the study found. Actually, “if women walked slowly, not only did they not control weight, they gained weight,” Harvard’s Dr. Anne Lusk, who was involved in the study, told Reuters Health.

This finding, Lusk said, contradicts the conventional wisdom that has driven physician recommendations for decades that any kind of walking is better than no walking at all.

SOURCE: Archives of Internal Medicine, June 28, 2010.