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RED-S and the Female Athlete Triad

Exercise in general is very beneficial. It helps improve cardiovascular health, reduces stress, and enhances our overall quality of life.

And yet if we aren't fueling our body appropriately for the amount of work we are asking it to perform, it can result in RED-S: Relative Energy Deficiency in Sport.

RED-S is when an athlete is not getting enough calories to support the extra energy needs required for their training and daily living, resulting in impaired physiological functioning, poor health, and declining athletic performance. This syndrome has been linked to impairments in bone health, metabolic rate, menstrual cycle, cardiovascular health, protein synthesis, immunity, and endocrine functioning, just to name a few.

RED-S can affect athletes of any gender and ability level.

Energy Deficiency

With enough fueling, rest, and recovery meals, most athletes will overcome the energy deficit created during training. However, if the body is not being restored appropriately, the deficit grows over time and eventually begins to affect physiological function and performance.

Low energy availability, or not getting enough calories, may often be accidental. This may occur because a newer athlete may not know how to fuel their workouts appropriately and understand how many calories they need to support good health and optimal performance.

On the other hand, the pressure of having a certain physique may cause the athlete to control their intake, often restricting specific food groups and total calories. This controlled eating may be anywhere on the disturbed eating spectrum, from disordered eating to a full-blown eating disorder.

Some sports – such as gymnastics, ice skating, diving, weight category sports, and endurance running or cycling – emphasize a smaller, or more controlled, physique, putting remarkable pressure on an athlete to restrict their food intake. RED-S can be more common among these groups of athletes.

The Female Athlete Triad

The Female Athlete Triad is a subset of RED-S.

This syndrome, which includes disordered eating, menstrual dysfunction, and reduced bone mineral density, can be present in female athletes of all levels; from high school girls just joining the gym or a team, to elite adult athletes. As with RED-S, the crux of the triad is low energy intake. This is particularly dangerous in adolescents when the body has a heightened need for growth and maturation, and when bone development and mineralization is at its peak.

Menstrual dysfunction is when menstruation does not happen on a consistent cycle. It may be too short, too long, or may stop altogether. Some athletes think missing their period means they are training well, but in reality, this should not be happening at all. Both training and weight fluctuations affect the hypothalamus, which in turn affects estrogen. Reduced estrogen then impacts the menstrual cycle.

Reduced bone mineral density is when the bone is not as strong as it should be, and is a stepping stone to osteoporosis. Causes include low estrogen (if the female has irregular or nonexistent periods), low body weight, or insufficient nutrient intake; particularly of protein, calcium, and vitamin D. Bone mineral density reaches its peak during adolescence and young adulthood, and if there are problems accruing enough bone during this time, a girl may never reach her full bone mineral density, leaving her more prone to fractures, breaks, and osteoporosis as an adult.

Symptoms of RED-S

Symptoms of RED-S include:

  • Rapid weight loss

  • Fatigue

  • Low libido (male athletes)

  • Delayed puberty or missed menstrual cycles (female athletes)

  • Hair loss

  • Frequent illness

  • Trouble staying warm

  • Difficulty focusing

  • Irritability or depression

Performance indicators of RED-S:

  • Impaired endurance

  • Decreased muscle strength

  • Decreased training response

  • Increased risk for injury

  • Decreased coordination

  • Decrease judgment and concentration

Prevention, Screening, and Treatment

Prevention of RED-S and Female Athlete Triad is key. Athletes, coaches, and parents should be educated on healthy eating habits and caloric needs for their sports, as well as appropriate fueling and recovery techniques for before, during, and after training.

Athlete Risk Categories

High Risk: Athletes with eating disorders, medical conditions related to low energy availability, or who have lost a significant amount of weight in a short period using extreme methods are at the highest risk for RED-S.

Moderate Risk: Athletes who have lost a significant amount of weight within the past month (5-10% of their body weight) or who have had a prolonged abnormally low body fat percentage, have irregular menstrual cycles, or a history of stress fractures or low bone mineral density are considered at moderate risk for RED-S.

Low Risk: Athletes who have an appropriate body composition that is maintained without stress or an unhealthy diet or exercise strategies; who have a healthy functioning endocrine system, and who have healthy bone mineral density for their age and sport are considered low risk for RED-S.


Athletes categorized in the Red or Yellow risk zones should receive a medical and nutrition evaluation and ensuing treatment. Treatment should include a team approach that may include a sports medicine physician, sports dietitian, exercise physiologist, athletic trainer, and sports psychologist. Of course, coaches and parents should be involved in management as well.

Treatment should focus on correcting energy balance by either increasing calories or decreasing output (training volume). Some athletes may need a focus on specific nutrients to help correct deficiencies.

Ongoing treatment and check-ins should be conducted by the team to ensure the athlete continues to improve, and eligibility to participate in athletic activities should be determined on an individual basis. If improvements are not made, the athlete may need to be taken out of training completely.

Physical activity is an important part of health and wellness, but as more people engage in training, it’s important to be aware of the potential health risks that are present and to screen for them.


Mountjoy M. Sundgot-Borgen J, Burke L, et al. RED-S CAT. Br J Sports Med 2015;49:421–423. doi:10.1136/bjsports-2014-094559.

Cabre HE, Moore SR, Smith-Ryan AE, Hackney AC. Relative Energy Deficiency in Sport (RED-S): Scientific, Clinical, and Practical Implications for the Female Athlete. Dtsch Z Sportmed. 2022;73(7):225-234. doi:10.5960/dzsm.2022.546.


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