This article explores how underfueling in endurance athletes can lead to altered cholesterol levels and negatively impact overall health. Endurance sports such as running, cycling, and triathlons demand high caloric intake to maintain energy balance. However, many athletes under consume calories, which can lead to Relative Energy Deficiency in Sport (RED-S). This condition affects multiple physiological systems, including hormone regulation, metabolism, and cholesterol balance.

When caloric intake is insufficient, the body's metabolism changes, resulting in higher levels of LDL cholesterol ("bad cholesterol") and lower levels of HDL cholesterol ("good cholesterol"). This altered lipid profile increases the risk of cardiovascular disease, even in athletes who "eat healthy" and maintain active lifestyles. Proper nutrition, balanced macronutrient intake, and regular health monitoring are essential to prevent RED-S and its effects on cholesterol and long-term health.