Athletes are sometimes told (or may believe) that losing weight and achieving a certain body composition will help improve their performance, but this is not necessarily true. Restricting our intake below what our body needs to function can lead to a sense of guilt around food, a feeling of shame about one’s body, and a negative impact on overall health and performance.

What is RED-S?

Relative Energy Deficiency in Sport (RED-S), formerly known as the Female Athlete Triad, is a syndrome in which low energy availability negatively affects several components of an individual’s health and performance. It includes both males and females of all age groups. Low energy availability is defined as a mismatch between the energy expended during exercise and energy taken in through food. When this energy deficiency occurs, the body cannot support its normal physiological processes. As a result, it tries to conserve energy by slowing down the resting metabolic rate, drawing on its own reserves for energy and eventually breaking down.


An athlete does not necessarily have to lose weight or be under-weight to have RED-S. Also, an eating disorder (or disordered eating) is not always present. Some people develop RED-S by simply being unaware of how many calories they need to eat, or they find it difficult to cook or eat regularly with their busy schedule. Low energy availability can also occur due to:

  • An unbalanced diet. A diet that is too high in fibre, low in fat and/or high in protein may prevent the athlete from consuming enough calories to meet his or her training demands. A diet too low in carbohydrates and fat can also impair hormone levels (such as estrogen, progesterone and testosterone), which play important roles in bone health and maintaining muscle mass.
  • Reduced appetite from increased exercise intensity.
  • Intentionally restricting food to lose weight. Excessive concern about eating and body weight can also be a source of stress that can affect both heath and performance. High stress levels increase a hormone called cortisol, which can lead to menstrual dysfunction and poor bone health.
  • The belief that decreased body weight and fat will improve performance. An initial weight loss may lead to better performance, but after a while, drastic weight loss can lead to overtraining, injuries and increased susceptibility to illness.
  • Societal pressure to eat a certain way or achieve an unrealistic body shape.

Effects on Health 

Low energy availability and inadequate nutrient intake can negatively affect a number of health parameters. Over time, this can lead to osteoporosis, stress fractures, chronic injuries, atherosclerosis, nutrient deficiencies and fertility issues. In the worst-case scenario, such as with an ongoing eating disorder, low energy availability can result in death if an athlete is severely underweight and malnourished.

A serious complication of RED-S is menstrual dysfunction, in the form of amenorrhea (absence of a menstrual period for more than three months) or oligomenorrhea (irregular cycles of more than 35 days). Simply put, it is not normal to miss your period while training. Sometimes, life stressors can disrupt a menstrual cycle, but any long-term disruption is a red flag that should be discussed with a medical doctor. It is important to note that exercise alone does not affect hormone levels or menstrual function, but low energy availability does.
Other effects of RED-S include:

  • Decreased testosterone levels
  • Increased stress fractures due to poor bone health
  • Increased episodes of illness (colds, sinus infections, sore throats, body aches)
  • Gastrointestinal symptoms such as constipation, bloating and cramps
  • Fatigue and poor sleep
  • Increased anxiety, depression, unstable mood, irritability, an inability to manage stress, fear of weight gain

Effects on Performance

Weight loss does not always help performance—in fact, it can be detrimental. When people drastically restrict calories, they are losing both fat and muscle mass. Poor nutrition can cause fatigue, illnesses and injuries that in turn will affect how well an athlete performs and adapts to training.
Other performance-related drawbacks of RED-S include:

  • Decreased performance
  • No improvement from training
  • Inability to run as fast or train as hard
  • Decreased coordination and concentration
  • Poor recovery
  • Decreased glycogen stores



The treatment of RED-S can include a full health care team: a doctor, dietitian and psychologist, if needed. The first line of treatment should be to optimize energy availability. Drugs will not correct the metabolic or endocrine changes associated with RED-S. Oral contraceptives are not recommended, because while they may mask the return of the menstrual cycle, bone loss and other health issues can still be ongoing.


Try to meet your daily energy needs. If appetite is decreased, a structured meal plan may help in understanding the amount of calories needed per day. Ensure you speak to a qualified Registered Sports Dietitian who can help you in this area. Many online diets underestimate calorie and nutrient needs.

Here are some basic nutrition guidelines to keep in mind:

  • Limit fibre intake to approximately 25 to 35 grams per day.
  • Ensure you are consuming enough carbohydrates and fat during the day. This will help replenish liver glycogen stores, ensure the brain receives enough glucose, and maintain normal hormone levels.
  • Eat frequently during the day.
  • Plan meals for the week and have some “ready to go” snacks and meals.
  • Do not skip meals or snacks.
  • Refuel post-exercise (carbohydrates and protein are both important). Smoothies are a great choice if your appetite is decreased after a workout.
  • Ensure you are meeting recommended intake levels of vitamin D (600 to 800 IU daily) and calcium (around 1000 mg daily for adults 19 to 50 years of age who are not in RED-S).
  • If safe to do so, incorporate strength training to optimize bone health.
  • Avoid excluding food groups unless necessary.


There is no ideal body weight or body composition to optimize performance. Instead, focus on optimizing energy and nutrient intake to support training and health. Start by building a healthy relationship with food and your body. Remember that health and happiness should be the focus if long term performance is a goal.

Be mindful about where your nutrition advice comes from and surround yourself by people (in person and on social media) who support your goals. Read athletes’ personal stories on trusted websites (a good example is Seek help from qualified professionals specializing in sports such as Registered Dietitians, doctors and psychologists if you have specific concerns.

If you fee like you are needing more guidance and support, you can book with me online.

I hope the information presented here will help athletes and coaches recognize RED-S and realize when additional support is needed. However, this article is not meant to act as a tool for self-diagnosis or treatment. Certain symptoms mentioned above, such as menstrual disorders or fatigue, can also occur from other medical conditions. Please speak with your family physician or a sports doctor for a comprehensive assessment and diagnosis. 


Originally posted on on January 23, 2020