One of our primary goals as physical therapists is to help athletes perform at their highest level while protecting their long-term health.
Relative Energy Deficiency in Sport (RED-S) occurs when an athlete does not consume enough energy to meet the physical demands of training and competition. This state of low energy availability can be intentional, such as purposeful dietary restriction, or unintentional, when fuel intake simply doesn’t match activity level.
When left unaddressed, RED-S can significantly affect health and performance.
How RED-S Impacts the Body and Performance
Low energy availability disrupts multiple systems in the body and may lead to:
Impaired metabolism
Disrupted menstrual function
Decreased bone density, increasing fracture and injury risk
Weakened immune function
Reduced protein synthesis and tissue recovery
Impaired cardiovascular health
From a performance standpoint, athletes may experience:
Decreased endurance and strength
Poor concentration and coordination
Slower reaction time
Impaired judgment during competition
RED-S affects female athletes more frequently, but male athletes can also be at risk. Studies report prevalence rates ranging from 22–58% across different sports.
Identifying Risk: RED-S Flag System
Early detection plays a critical role in preventing long-term complications and protecting athletic performance.
Red Flags
Diagnosed eating disorders, including anorexia nervosa
Extreme or unsafe weight-loss practices
Significant psychological or physiological effects related to low energy availability
Management:
No competition
Supervised training only after clearance from medical specialists
Yellow Flags
Low body fat percentage
Significant weight loss or poor growth patterns
Hormonal irregularities
Reduced bone density
Inconsistent or inadequate nutrition habits
Management:
May compete once medically cleared
Training permitted if aligned with a structured treatment plan
Green Flags
Consistent, healthy eating patterns
Normal hormonal and metabolic function
Bone density appropriate for age, sport, and ethnicity
No ongoing musculoskeletal concerns
Management:
Full sport participation
Strategies to Reduce the Risk of RED-S
Optimize Nutrition
Encourage consistent, balanced fueling
Recognize how under-fueling impacts both health and performance
Adjust calorie intake as training volume or intensity increases
Promote Body Positivity
Shift focus away from weight and toward health and performance
Set realistic, health-centered goals for body composition
Avoid negative or critical comments about body shape or size—both toward athletes and yourself
Monitor Health Regularly
Encourage annual wellness visits with a physician
Watch for red flags and follow up early with a therapist or healthcare provider
Learning to recognize the signs of RED-S, prioritizing proper fueling, and addressing concerns early can protect athlete health and support long-term performance.
If you have questions or concerns about RED-S, injury risk, or fueling for sport, reach out to a qualified healthcare provider or physical therapist for guidance.
REFERENCES:
Burke LM, Lundy B, Fahrenholtz IL, Melin AK. Pitfalls of conducting and interpreting estimates of energy availability in free-living athletes. Int J Sport Nutr Exerc Metab. 2018;28(4):350-363.
Coelho AR, Cardoso G, Brito ME, Gomes IN, Cascais MJ. The female athlete triad/relative energy deficiency in sports(Red-s). Rev Bras Ginecol Obstet. 2021;43(5):395-402.
Johnston K. Sports medicine: relative energy deficiency in sport. FP Essent. 2022;518:18-22.
Logue DM, Madigan SM, Melin A, et al. Low energy availability in athletes 2020: an updated narrative review of prevalence, risk, within-day energy balance, knowledge, and impact on sports performance. Nutrients. 2020;12(3):835.
Mountjoy M, Sundgot-Borgen J, Burke L, et al. The ioc consensus statement: beyond the female athlete triad–relative energy deficiency in sport(Red-s). Br J Sports Med. 2014;48(7):491-497.
Mountjoy M, Sundgot-Borgen JK, Burke LM, et al. IOC consensus statement on relative energy deficiency in sport (Red-s): 2018 update. Br J Sports Med. 2018;52(11):687-697.
