"There was a significant interaction with body mass index (BMI), such that there was an inverse dose-response relation between activity levels and weight gain among women with a BMI of less than 25 but no relation among women with a BMI from 25 to 29.9 or with a BMI of 30.0 or higher. A total of 4,540 women (13.3 percent) with a BMI lower than 25 at study start successfully maintained their weight by gaining less than 5.1 lbs. throughout. Their [average] activity level over the study was 21.5 MET hours per week ([approximately] 60 minutes a day of moderate-intensity activity)," the researchers write.

"These data suggest that the 2008 federal recommendation for 150 minutes per week, while clearly sufficient to lower the risks of chronic diseases, is insufficient for weight gain prevention absent caloric restriction. Physical activity was inversely related to weight gain only among normal-weight women; among heavier women, there was no relation, emphasizing the importance of controlling caloric intake for weight maintenance in this group."

Source: JAMA