Context. There is debate over the independent and combined effects of dieting and increased physical activity on improving metabolic risk factors (body composition and fat distribution). Objective. Conduct a randomized controlled trial (CALERIE) to test the effect of a 25% energy deficit by diet alone or diet plus exercise for 6 months on body composition and fat distribution. Design. Randomized controlled trial. Setting: Institutional Research Center. Participants. Thirty-five out of 36 overweight but otherwise healthy participants (16M/19F) completed the study. Intervention. Participants were randomized to either control (healthy weight-maintenance diet, n=11), calorie restriction (CR: 25% reduction in energy intake, n=12) or caloric restriction+exercise (CR+EX: 12.5% reduction in energy intake+12.5% increase in exercise energy expenditure, n=12) for 6 months. Main outcome measures. Changes in body composition by DXA and changes in abdominal fat distribution by multislice CT. Results. The calculated energy deficit across the intervention was not different between CR and CR+EX. Participants lost 10% of body weight (CR:-8.3±0.8, CR+EX:-8.1±0.8kg, p=1.00), 24% of fat mass (CR:-5.8±0.6, CR+EX:-6.4±0.6kg, p=0.99), and 27% of abdominal visceral fat (CR:0.9±0.2, CR+EX:0.8±0.2kg, p=1.00). Both whole body and abdominal fat distribution were not altered by the intervention. Conclusion. Exercise plays an equivalent role to CR in terms of energy balance; however it can also improve aerobic fitness which has other important cardiovascular and metabolic implications.