The Effect of Exercise on Leptin and Adiposity: A Systematic Review

Introduction: Leptin has been characterized as an important regulator of metabolic homeostasis, functioning in the inhibition of food intake and promotion of energy expenditure. Leptin resistance has been implicated in the development of cardiovascular diseases and obesity, and as exercise programs are used as a therapeutic measure for these disorders, it is hypothesized that exercise will decrease concentrations of leptin in the blood. Methods: A comprehensive literature search of MedLine was conducted from inception to September 2020. Relevant search terms include: Leptin, Obesity, Exercise, Physical activity, BMI, and Adiposity. Eligible randomized control trials (RCTs) include RCTs reporting on the effects of low, moderate or high intensive exercise on leptin concentration. We followed the search strategy based on PRISMA to report our systematic review, and assessed the studies independently and in duplicate for their risk of bias (ROB) using the Cochrane ROB2 tool. Statistical analysis was performed to compare ROB (categorized as “high” or “low/some”) in relation to impact factor, number of citations, and number of authors. Results: Forty-eight studies involving the relationship between physical exercise and leptin met the inclusion criteria. After completing the ROB, the relationships between ROB and impact factor (0.2775, p > 0.6405), citation number (2.059, p > 0.0962), and the number of authors (-5.235, p > 0.5551) were determined. Discussion: The leptin pathway involves an overactivation of mTOR contributing to the development of obesity, with this pathway being inhibited by physical activity. This corresponds to the findings that thirty-nine studies reported that physical exercise resulted in a statistically significant decrease in leptin levels as compared to the control group. However, the overall evidence was insufficient to suggest a statistically significant relationship between ROB and impact factor, citation number, and the number of authors. Conclusion: This systematic review indicated an inverse relationship between physical exercise and leptin However, further research is needed to address the varying effects of physical activity on leptin and to define a more concrete relationship between risk of bias and the characteristics of studies in this field.