In 2008, U.S. guidelines recommended at least 150 minutes of moderate intensity activity per week for substantial health benefit. However, it is not clear how much physical activity is needed to prevent long-term weight gain. A new study published in the March 24/31 edition of the Journal of the American Medical Association shows that women need 60 minutes of moderate exercise a day to prevent weight gain as they age if they consume a normal diet.

Researchers from Harvard Medical School and their colleagues examined the association of different amounts of physical activity with long-term weight changes among women with an average age of 54.2 years who ate a normal diet The study involved over 34,000 women who reported their exercise and body weight at three-year intervals from 1992 to 2007. Overall, the women in the study gained an average of 2.6 kg (5.7 pounds) throughout the study. Women who were a normal weight, defined as a body mass index less than 25, were able to maintain their weight if they did either 30 minutes of intense physical activity or 60 minutes of moderate-intensity exercise a day. However, for overweight or obese women, 60 minutes of moderate-intensity activity was not enough to maintain weight.

The findings of this study suggest that women need more exercise than the current federal guidelines recommend in order to maintain weight if they continue to consume a normal diet. However, the findings do align with a 2002 Institute of Medicine report that suggested 60 minutes of exercise a day to prevent weight gain. What this means is, women who exercise less will likely need to cut calories in order to maintain their weight.

Source:

JAMA. 2010; 303(12): 1173-1179.