In a paper, published in JAMA in 2010, the association of different amounts of physical activity with long-term weight changes among women consuming a usual diet was examined.
The amount of physical activity needed to prevent long-term weight gain is unclear. In 2008, federal guidelines recommended at least 150 minutes per week (7.5 metabolic equivalent [MET] hours per week) of moderate-intensity activity for “substantial health benefits.”
A prospective cohort study involving 34 079 healthy US women (mean age, 54.2 years) from 1992-2007 was designed. At baseline and months 36, 72, 96, 120, 144, and 156, women reported their physical activity and body weight.
Activities were classified in three groups:
- Less than 7.5,
- 7.5 to less than 21,
- 21 or more MET hours/week of activity
Repeated-measures regression prospectively examined physical activity and weight change over intervals averaging 3 years.
Main Outcome Measure Change in weight.
Results: Women gained a mean of 2.6 kg throughout the study. A multivariate analysis comparing women in groups 2 and 3 showed that group 2 women gained a mean (SD) 0.11 kg (0.04 kg; P = .003) over a mean interval of 3 years, and those expending less than 7.5 MET hours per week gained 0.12 kg (0.04; P = .002). 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 (P for trend < .001) but no relation among women with a BMI from 25 or higher (P for trend = .50). 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 (about 60 minutes a day of moderate-intensity activity).
Conclusions
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 60 minutes a day of moderate-intensity activity throughout the study.
(From: Physical Activity and Weight Gain Prevention, I-Min Lee, MBBS, ScD et al., JAMA. 2010;303(12):1173-1179)