Effect of long-term changes in diet and exercise on plasma leptin concentrations

Background: Although it is known that plasma leptin concentrations correlat e with the amount of adipose tissue in the body, little information is avai lable on the long-term effects on leptin concentrations of changes in diet and exercise. Objective: We wanted to examine whether changes in dietary energy sources a nd exercise-mediated energy expenditure, alone or in combination, affect pl asma leptin concentrations. Design: In a randomized, 2 x 2 factorial trial, 186 men with metabolic synd rome were divided into 4 groups: diet, exercise, a combination of diet and exercise, and control. Data on dietary intake, physical fitness, and demogr aphics were collected and plasma leptin concentrations were measured before and after a 1-y intervention period. Results: Plasma leptin concentrations, body mass index, and fat mass decrea sed in association with long-term reductions in food intake as well as incr eased physical activity. By adjusting for either body mass index or fat mas s, we observed a highly significant reduction in plasma leptin concentratio n after both the diet and the exercise interventions. There was no interact ion between the interventions, suggesting a direct and additive effect of c hanges in diet and physical activity on plasma leptin concentrations. Conclusion: Long-term changes in lifestyle consisting of decreased intake o f dietary fat and increased physical activity reduced plasma leptin concent rations in humans beyond the reduction expected as a result of changes in f at mass.