The Concept and Physiological Consequences of Energy Deficiency in Sports Nutrition

Abstract

Recently, many studies on energy deficiency in athletes have been conducted worldwide. Energy deficiency in athletes does not present as negative energy balance; it presents as low energy availability (EA).EA is defined as energy intake minus exercise energy expenditure, divided by fat-free mass. Exposure of athletes to low EA has been reported causing a variety of signs and symptoms described in the international consensus on relative energy deficiency in sport (REDs). Chronic low EA affects many physiological functions. For example, the endocrine system is disturbed, resulting in such issues as reduced thyroid and sex hormones and elevated cortisol levels. Subsequently, energy metabolism is suppressed, and resting energy expenditure is reduced. In female athletes, low EA causes menstrual disorders including amenorrhea, and in male athletes, a decrease in gonadal function, leading to impaired reproductive function in both sexes. In addition, decreased bone formation and increased bone resorption lead to low bone mineral density, increasing the risk of stress fractures. For the early detection and prevention of energy deficiency, monitoring the markers related to the results of nutritional assessment, including changes in surrogate markers of EA, is crucial and highlights the important role of sports/registered dietitians.