How much exercise is enough to prevent weight gain?

January 01, 0001

How much exercise is enough to prevent weight gain?

Physical activity is often touted as one of the keys to maintaining good health and controlling weight. In 2008, US guidelines recommended a minimum of 150 minutes per week of moderate-intensity activity. However, the amount of physical activity needed to prevent long-term weight gain is unclear. These US researchers examined the association of physical activity with long-term weight changes among women consuming a usual diet. They performed a prospective cohort study involving 34,079 healthy women (mean age, 54.2 years) from 1992-2007. These women reported their physical activity and body weight at multiple times over 13 years. The participants were grouped as expending less than 7.5, 7.5 to less than 21, and 21 or more MET hours per week of activity at each reporting.

The researchers report: "Women gained a mean of 2.6 kg throughout the study. A multivariate analysis comparing women expending 21 or more MET hours per week with those expending from 7.5 to less than 21 MET hours per week showed that the latter group gained a mean 0.11 kg over a mean interval of 3 years, and those expending less than 7.5 MET hours per week gained 0.12 kg. 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 4540 women (13.3%) with a BMI lower than 25 at study start successfully maintained their weight by gaining less than 2.3 kg throughout. Their mean activity level over the study was 21.5 MET hours per week (60 minutes a day of moderate-intensity activity)."

The authors concluded: "Among women consuming a usual diet, physical activity was associated with less weight gain only among women whose BMI was lower than 25. Women successful in maintaining normal weight and gaining fewer than 2.3 kg over 13 years averaged approximately 6o minutes a day of moderate-intensity activity throughout the study."

Exercise has numerous benefits, but this study suggests it is most effective at maintaining weight in females if they are non-obese to begin with and the amount of exercise required to do so is in excess of current guidelines

For the full abstract, click here.

JAMA 303(12):1173-1179, 24 March 2010
© 2010 the American Medical Association
Physical Activity and Weight Gain Prevention. I-Min Lee, Luc Djoussé, Howard D. Sesso, Lu Wang, and Julie E. Buring.

Category: T. Endocrine/Metabolic/Nutritional. Keywords: exercise, weight gain, women, MET, BMI, prospective cohort study, journal watch.
Synopsis edited by Dr Paul Schaefer, Toledo, Ohio. Posted on Global Family Doctor 13 April 2010

Pearls are an independent product of the Cochrane primary care group and are meant for educational use and not to guide clinical care.