Health effects resulting from exercise versus those from body fat loss

Objective: The purpose of this review was to assess whether body weight con founds the relationships between physical activity and its health benefits. Methods: The review includes 80 reports from population-based studies (Evi dence Category C) of physical activity or fitness and cardiovascular diseas e (CVD) or coronary heart disease (CHD). Results: Eleven of 64 reports on a ctivity found no relationship between physical activity and disease. Of the remaining 53 reports, 11 did not address the possible confounding effects of body weight, nine cited reasons that weight differences should not expla in their observed associations, and 33 statistically adjusted for weight (a s required). Only three of these changed their associations from significan t to nonsignificant when adjusted. Ten of 16 reports on cardiorespiratory f itness and CHD or CVD used statistical adjustment, and none of these change d their findings to nonsignificant. Population studies show that vigorously active individuals also have higher high-density lipoprotein (HDL)-cholest erol concentration, a major risk factor for CHD and CVD, than sedentary ind ividuals when statistically adjusted for weight. In contrast, intervention studies, which relate dynamic changes in weight and HDL, suggest that adjus tment for weight loss largely eliminates the increase in HDL-cholesterol in sedentary men who begin exercising vigorously. Adjusting the cross-section al HDL-cholesterol differences for the dynamic effects of weight loss elimi nates most of the HDL-cholesterol difference between active and sedentary m en. Conclusion: Population studies show that the lower incidence of CHD and CVD and higher HDL of fit, active individuals are not because of lean, hea lthy individuals choosing to be active (i.e., self-selection bias). Neverth eless, metabolic processed associated weight loss may be primarily responsi ble for the HDL differences between active and sedentary men, and possibly also their differences in CHD and CVD.