Association of physical activity intensity levels with overweight and obesity in a population-based sample of adults.

Background: Clarify the association between physical activity intensity and overweight/obesity.
Methods: Population-based 1997-2001 survey in Geneva, Switzerland (n=5,757, ages 35 to 74). Intensity of physical activity energy expenditure (EE) defined as percentage of total EE in moderate activities [3-3.9 x basal metabolism rate (BMR), e.g., normal walking, household chores] and high-intensity activities (> or =4 x BMR, e.g., brisk walking, sports). Overweight or obesity based on measured body mass index (BMI).
Results: Comparing participants in the lowest vs. the highest tertile of the percentage of high-intensity EE, the odds ratios (ORs) were, for obesity vs. normal weight, 2.8 (95% confidence interval: 2.0-3.8, P<0.0001) in men and 2.4 (1.7-3.4, P<0.0001) in women. For obese vs. overweight, the men/women ORs were 1.9 (1.4-2.6, P<0.0001)/1.5 (1.0-2.2, P<0.05). For overweight vs. normal weight, the men/women ORs were 1.4 (1.1-1.7, P<0.002)/1.7 (1.3-2.1, P<0.0001). Less or no relationship was found for the percentage of moderate-intensity EE.
Conclusions: This cross-sectional study cannot determine whether exercise is an effective strategy for weight control or whether overweight or obese people exercise less. However, clear dose-response associations in both genders between obesity or overweight and energy expenditure in high (but not in moderate)-intensity activities are findings with potentially major public health implications meriting validation in an experimental intervention study.