The Effect of Chronic Exercise Training on Leptin: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background Leptin is a hormone associated with satiety, lipid oxidation, energy expenditure, and energy homeostasis. To date, the current body of research examining the effect of chronic exercise training on leptin has yielded inconsistent results. Objective The purpose of this meta-analysis was to provide a quantitative estimate of the magnitude of change in leptin levels following participation in exercise interventions lasting >= 2 weeks. Methods All studies included were peer-reviewed and published in English. To be included, studies randomized human participants to an exercise training group or nonexercise comparison group for an exercise training intervention. Leptin levels were measured at baseline, during, and/or after completion of the exercise training program. Random-effects models were used to aggregate a mean effect size (ES) and 95% confidence intervals (CIs), and identify potential moderators. Results Seventy-two randomized controlled trials met the inclusion criteria and resulted in 107 effects (n = 3826). The mean ES of 0.24 (95% CI 0.16-0.32, p < 0.0001) indicated a decrease in leptin following an exercise training program. A decrease in %Fat (beta = - 0.07, p < 0.01) was associated with a decrease in leptin after accounting for the type of control group (beta = - 0.38, p < 0.0001) used in each study. Conclusion These results suggest that engaging in chronic exercise training (>= 2 weeks) is associated with a decrease in leptin levels for individuals regardless of age and sex. However, a greater decrease in leptin occurred with a decreased percentage of body fat.