Background

Relative energy deficiency in sport (RED-S) is the result of insufficient caloric intake and/or excessive energy expenditure. Consequences of this low-energy condition can alter many physiological systems, including metabolism, menstrual function, bone health, immunity, protein synthesis, and cardiovascular and psychological health1 (figure 1).

The RED-S concept has been adapted from a previously identified syndrome, the female athlete triad, which affects active women with low-energy availability, menstrual dysfunction and low bone mineral density.2 Emerging data suggest there may be a parallel syndrome in undernourished male athletes with resulting hypogonadotropic hypogonadism and impairment of bone health.3 RED-S is a comprehensive model depicting a low-energy status in physically active women or men.

Case

A 29-year-old male runner presents for evaluation with concerns of fatigue and poor athletic performance. Over the past year, he has focused on his training, running approximately 72 miles per week and performing yoga 3 days per week. He also has revised his diet to eat ‘healthy’ and avoid alcohol, and subsequently lost 21 lbs. The …