In a comprehensive review, researchers have outlined new insights into Relative Energy Deficiency in Sport, a condition affecting both athletes and military personnel that stems from inadequate caloric intake relative to energy expenditure.
In the review, published in Endocrine Reviews, researchers from Harvard Medical School and international collaborators emphasized that Relative Deficiency in Sport (REDs) may encompass more than just the traditionally recognized Female Athlete Triad (menstrual dysfunction, low bone mineral density, and disordered eating). The syndrome can affect both sexes and involves multiple physiological systems.
In sports science, energy availability is defined as the difference between total daily energy intake and exercise energy expenditure divided by fat-free mass. The researchers noted that while an energy availability of at least 45 kcal/kg fat-free mass per day is typically recommended for optimal physiological function, levels below 30 kcal/kg fat-free mass per day can trigger substantial systemic disruptions.
Key findings indicated that prolonged energy deficiency disrupts several endocrine pathways. In males, studies showed testosterone levels could reach extremely low testosterone levels following prolonged ranger training courses. Female athletes showed higher rates of menstrual irregularities, with up to 50% experiencing disruptions. The highest prevalence for primary amenorrhea was reported in rhythmic gymnastics (25%), secondary amenorrhea in cycling (56%), and oligomenorrhea in boxing (55%).
Military personnel faced particularly high risks. Studies revealed stress fracture incidence of 2.05 vs 7.47 per 1,000 person-years in male and female soldiers respectively, representing over 5.2 million person-years of risk. Other reports showed incidence rates of 19.3 vs 79.9 per 1,000 recruits for general stress fractures. These injuries impose an estimated cost of $100 million annually to the U.S. military, not including lost duty time.
The researchers identified leptin, a hormone produced by fat tissue, as a potential key regulator in REDs. When energy availability is low, leptin levels drop, triggering various physiological adaptations. While leptin replacement therapy has shown potential in preliminary studies, the researchers emphasized it is not currently recommended pending further research.
The review discussed several ongoing clinical trials investigating both prevention strategies and treatments. Current recommendations focused on nutritional and behavioral modifications rather than pharmacologic interventions, including increasing daily caloric intake by 300 to 600 kcal and maintaining a minimum of 2,000 kcal/day, depending on activity level.
Recent studies demonstrated that increased energy intake 20% to 40% above baseline energy requirements was associated with improved menstrual function in exercising women with oligomenorrhea or amenorrhea. Additionally, vitamin D and calcium supplementation showed potential benefits during recovery, with optimal daily intake recommendations of 1,000 to 1,300 mg of calcium and vitamin D concentrations within 32 to 50 ng/mL.
The International Olympic Committee has incorporated these findings into its 2023 consensus statement on REDs, reflecting the evolving understanding of this condition in sports medicine and military health.
The authors declared having no competing interests.
