Relative Energy Deficiency in Sport (REDs) and Its Effect on Health and Performance in Men: A Systematic Review of Cross-Sectional Studies.

Background : Relative Energy Deficiency in Sport (REDs) poses a significant challenge to both health and performance in male athletes. This systematic review aimed to evaluate the effects of REDs on various health and performance parameters in male athletes. Methods : A comprehensive literature search was conducted up to April 2024, using four databases: PubMed, Scopus, Web of Science, and SPORTDiscus. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Cross-sectional studies investigating the relationship between energy availability (EA) and metabolic and hormonal biomarkers, as well as athletic performance in male athletes, were included. The methodological quality of the selected studies was assessed using a modified version of the McMaster scale. Results : A total of 10 studies, comprising 308 participants, were included in this systematic review. Low energy availability was associated with significant reductions in resting metabolic rate (RMR) and RMR ratio, as well as increased cortisol levels and decreased athletic performance. However, no significant changes were observed in bone mineral density or in levels of testosterone, triiodothyronine, and insulin-like growth factor 1. Conclusions : REDs impacts male and female athletes differently, highlighting the need for further studies to determine the critical EA thresholds that trigger negative effects in male athletes. Registration: This systematic review was prospectively registered with the PROSPERO International prospective register of systematic reviews (PROSPERO registration ID number: CRD42024565897).