Leptin, derived from the Greek word “leptose” meaning thinness, was discovered in 1994 through the isolation of the obesity gene. This protein hormone, with a helical structure akin to cytokines, is primarily produced and released by subcutaneous fat cells in a pulsatile pattern, peaking near midnight. Leptin plays an important role in regulating energy balance and metabolism, and significantly influences body weight. Despite extensive research on leptin, studies on the effect of physical activity on leptin secretion from adipose tissue have yielded inconsistent results. This review examines a variety of studies that explore how different intensities of physical activity affect leptin levels, focusing particularly on its response to intense exercise and training periods. Findings on the relationship between physical activity and leptin are mixed, with some researchers suggesting that exercise can reduce leptin concentrations, particularly depending on the duration of exercise and caloric expenditure, while others report no significant change. The current review suggests that physical activity lasting over 60 minutes and involving substantial energy expenditure (> 800 kcal) is required to observe reductions in plasma leptin concentrations, especially in non-athletes.
