Relative energy deficiency in sport (RED- S)

Relative Energy Deficiency in Sport (RED-S) refers to a condi-tion in which energy imbalance leads to impaired physiologi-cal function of multiple organ systems and expands on the diagnosis previously known as the Female Athlete Triad. Researchers attribute the medical complications of RED-S to low energy availability, in which energy availability is defined as dietary energy intake minus exercise energy expenditure divided by fat-free mass. This article reviews the history of this diagnosis, the changing terminology, and the reasons for the expansion. Accepted definitions of each part of the energy availability equation are considered and the difficulties that exist using these equations in practice or com-paratively in the literature are assessed. The review analyzes the broad spectrum of health consequences of RED-S, espe-cially as it relates to hypoestrogenemia and menstrual func-tion, gives guidance to those caring for athletes on the identification and management of RED-S, and sheds lights on the important role of coaches, athletic trainers, and families in recognizing this diagnosis and in helping getting patients to care.