Weight Loss First, Then Exercise

Physical activity has no more than a modest beneficial effect of lowering risk of chronic disease in obese individuals, according to a published review.

Peter T. Katzmarzyk, Ph.D., from the Pennington Biomedical Research Center in Baton Rouge, La, and Scott A. Lear, Ph.D., from the Simon Fraser University in Vancouver, Canada, reviewed available literature published before March 2010 to assess the effectiveness of physical activity in improving chronic disease risk factors in obese individuals. A total of 44 randomized trials of at least 10 weeks duration, with a sample mean body mass index of 30 kg/m² or more at baseline, and reporting a relevant risk factor were included.

The investigators found that, in obese individuals, physical activity had only a modest effect on chronic disease risk factors, with substantial heterogeneity in responses of risk factors across the studies. The characteristics of the exercise interventions also showed great heterogeneity. In many of the studies, it was difficult to identify the impact of physical activity, which was independent of changes to the body mass index that resulted from the intervention.

"Obese individuals should be encouraged to undertake physical activity following general recommendations for weight loss and health; the degree to which physical activity is effective at lowering risk factor levels among high-risk obese individuals is not known," the authors write.

Obesity Reviews, Sept 26, 2011