Exercise in combination with diet improves short-term weight loss and helps maintain weight loss over the long term, but the optimal exercise regimen for long-term weight loss has not been established. Current recommendations range from 30 to 60 minutes of moderate-intensity exercise on most days, depending on whether the goal is to improve health or to control weight. There are no data from long-term clinical trials to determine whether exercise duration or intensity have a greater impact on body weight. In this study, Jakicic and colleagues examine the differential effect of moderate versus high duration and moderate versus vigorous exercise on weight loss and cardiorespiratory fitness following 12 months of treatment in overweight women.

Healthy, sedentary, nonpregnant women aged 21 to 45 years with a body mass index (BMI) between 27 and 40 were enrolled in the study. All participants were instructed to follow a low-calorie, low-fat diet, reinforced by a behavioral weight loss intervention involving group meeting and periodic telephone calls. Participants were randomized to one of the following four exercise groups: (1) vigorous intensity/high duration; (2) moderate intensity/high duration; (3) moderate intensity/moderate duration; or (4) vigorous intensity/moderate duration. Outcomes based on BMI were assessed at baseline and at six and 12 months. A graded exercise treadmill test assessed cardiorespiratory fitness. An exercise log contributed to the analysis.

In the 184 women who completed the study, weight loss was significant in all groups, but there was no significant effect of either exercise duration or exercise intensity on changes in body weight between groups. In kilograms, the mean weight loss at 12 months was 8.9 (vigorous intensity/high duration), 8.2 (moderate intensity/high duration), 6.3 (moderate intensity/moderate duration), and 7.0 (vigorous intensity/moderate duration); (P <.001). Cardiorespiratory fitness increased significantly in all groups, but there were no significant effects of exercise duration or intensity on changes in cardiorespiratory fitness measures at the end of the study period.

Post-hoc analysis showed that when participants were grouped on the basis of the amount of physical activity that was at least moderate intensity, those with 200 minutes per week of exercise lost significantly more weight than those with exercise of less than 150 minutes per week. A similar difference held true for cardiorespiratory fitness. Neither weight loss nor cardiorespiratory fitness in the 150 minute per week exercise group differed from those of the other groups.

In this study, which compared differences in exercise duration (moderate versus high) and intensity (moderate versus vigorous), higher amounts of exercise resulted in a 10 percent weight loss compared with lesser amounts of exercise duration and intensity that resulted in an 8 percent weight loss, a nonsignificant difference. These findings, which presuppose a concomitant weight-reduction diet, suggest that working toward the Institute of Medicine’s recommended goal of 60 minutes of exercise per day may result in optimal weight reduction and weight loss maintenance.