What role does Insulin play in Sport?

Insulin plays a central but nuanced role in sport. As an anabolic hormone, it promotes glucose uptake into muscle cells and glycogen synthesis, which is critical for post-exercise recovery. At the same time, insulin inhibits fat oxidation, which can be disadvantageous for endurance athletes during prolonged exertion. Insulin sensitivity—the ability of cells to respond to insulin—is improved by regular training, especially resistance and high-intensity interval training. A well-trained muscle requires less insulin to take up glucose. Consumer DNA or biomarker tests that claim to measure insulin resistance or genetic variants (e.g., in IRS1) often provide weak associations and are not diagnostic. The evidence is largely mechanistic, based on physiological principles rather than large intervention trials. For athletes, maintaining stable blood glucose is more important than isolated insulin values. Supplements like chromium or berberine are sometimes marketed to enhance insulin sensitivity, but the data are mixed. Safety note: extreme manipulation of insulin levels (e.g., through severe carbohydrate restriction or exogenous insulin) is dangerous without medical supervision. In summary, insulin is a key hormone for recovery and muscle growth, but its impact on performance is context-dependent and modulated by training and nutrition.