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Energy Availability and the Female Athlete

By USA Hockey, 04/21/17, 8:30AM MDT


RED-S and athlete health and wellness

Meeting energy requirements for female athletes is often challenging, especially teen athletes who are still growing. Athletes, parents, coaches, and health-care practitioners should be aware of the health implications that can arise when calorie intake does not meet the energy needs of training, competition, and normal growth.

Energy Availability (EA) is the term that describes the amount of calories remaining for body functions after deducting for calories used during exercise. When an athlete has low EA, performance can suffer, injuries can increase, and most importantly – normal health can be adversely affected.    

The International Olympic Committee (IOC) has combined these factors into the Relative Energy Deficiency in Sports (RED-S) – an evolution from the Female Athlete Triad. Although RED-S affects both genders, it has a higher prevalence in females.

The Female Athlete Triad consists of three inter-related components:  energy availability, menstrual function, and bone health. RED-S adds these three components to several physiological impairments, including metabolic rate, immunity, protein synthesis, and cardiovascular health. In simple terms, RED-S results when caloric intake is insufficient to support daily activity, healing, and health.

Bone health is a major concern in female athletes, specifically growing teens, because the ability to build bone mass is at its highest during teenage years. Insufficient EA can decrease bone mass, and a diet focused on intentionally restricting calories can be low in calcium and vitamin D, two nutrients essential to bone health.

When EA is low, estrogen levels can fall, leading to irregular or missed menstrual cycles and hormonal changes. Athletes should be aware of changes in their EA caused by such factors as training load, performance goals, in-season versus off-season needs, intentional or unintentional decreases in caloric intakes, and response to injury or illness.

Athletes often notice a change in performance before they recognize a health-related issue. The IOC position statement on RED-S identifies multiple negative effects:

  • Decreased muscle strength
  • Decreased glycogen stores
  • Decreased endurance performance
  • Decreased training response
  • Increased injury risk
  • Decreases in coordination
  • Decreased concentration
  • Depression and irritability

RED-S puts every athlete at risk. While most of the research is on female athletes, low EA can impact testosterone levels in men. Unlike missed menstrual cycles in female athletes, hormonal changes in male athletes can go unnoticed.

The IOC identifies the following factors to help ensure low-risk participation in sports:

  • Healthy eating habits with appropriate EA
  • Normal hormonal and metabolic function
  • Healthy bone density
  • Healthy musculoskeletal system

Moderate-risk factors in sports participation include:

  • Prolonged low percent body fat
  • Weight loss between 5-10 percent in one month
  • Changes in expected growth and development in adolescent athletes
  • Abnormal menstrual cycle in females
  • Abnormal hormone profile in males
  • Reduction in bone density
  • History of one or more stress fractures associated with hormonal dysfunction and/or low EA
  • Physical/psychological complications related to low EA/disordered eating
  • Prolonged relative energy deficiency
  • Disordered eating behaviors negatively affecting team members
  • Lack of progress in treatment and/or non-compliance

Athletes and their parents should work with their coaches and health-care practitioners to assess the demands of their sport and its training, and adapt caloric intakes to best meet the performance and health needs of the athlete.


The IOC Consensus Statement: Beyond the Female Athlete Triad – Relative Energy Deficiency in Sport (RED-S). National Center for Biotechnology Information, U.S. National Library of Medicine,

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