Systematic Review: Does Exercise Training Influence Ghrelin Levels?

Ghrelin, a gastric-derived peptide, regulates appetite, food intake, and energy homeostasis. Body weight plays a crucial role in modulating circulating ghrelin levels. Since exercise training is one of the most valuable tools for controlling body weight, it is relevant to consider whether exercise can influence total ghrelin secretion. This study aims to perform a systematic review of the effect of acute/chronic exercise on plasma ghrelin levels. An extensive literature search was carried out on various databases, including PubMed, ScienceDirect, and Google Scholar. The search was conducted using English keywords such as acute-exercise, transient-exercise, exercise, chronic-exercise, training, physical-activity, physical-training, exercise training, and total-ghrelin, ghrelin, appetite-related-peptides, gastrointestinal-peptides, gastrointestinal-hormones, and appetite-regulating-hormone. Initially, 2104 studies were identified. After evaluating study quality, data from 61 relevant studies were extracted for inclusion in this review. Most studies indicated that short-term acute aerobic exercise did not affect total ghrelin levels regardless of exercise intensity, characteristics, or growth hormone (GH) secretion. However, long and very-long aerobic/chronic exercise increased total ghrelin levels, mainly in overweight/obese individuals. Acute/chronic exercise may differentially influence total ghrelin secretion. Short-term acute aerobic exercise induces stable plasma ghrelin concentrations, independent of GH secretion. Long-term aerobic training increased its levels mainly in overweight/obese individuals through body composition and oxidative stress reduction. Additionally, total ghrelin secretion is more sensitive to exercise/training duration than exercise/training intensity.