(March 23, 2010 - Insidermedicine)

About an hour of moderate-intensity activity daily could be enough to prevent weight gain among women of normal weight, but it may not be so easy for women who are already overweight, according to research published in the Journal of the American Medical Association.

Some examples of moderate physical activity include:

•    Washing and waxing a car

•    Playing volleyball

•    Walking at a rate of approximately 3 miles an hour

Researchers from Brigham and Women’s Hospital in Boston followed over 34,000 healthy women from 1992 to 2007. About every three years, the women reported their level of physical activity and their weight. The women were then classified into one of three categories based on their average weekly activity levels.

Among women of normal weight, increasing activity level was associated with less weight gain over time. In contrast, increasing activity level did not appear to slow weight gain in overweight and obese women. Among normal weight women, about 13% were able to maintain their weight throughout the entire 15-year study period. These women engaged in an average of 60 min of moderate-intensity activity every day.

Today’s research suggests that weight control may be more difficult for women when they are overweight. It also suggests that normal weight women may be able to maintain their weight by engaging in at least 60 min of moderate-intensity physical activity daily.