Menstrual Period: Relative Energy Deficiency in Sports

Most girls who play sports have regular menstrual periods, and girls who are very active may skip a few periods. However, some girls who train really hard and don’t get enough nutrition may skip many menstrual periods, or they may get their period at a later age than usual, especially if they’ve lost weight, are not taking in adequate nutrition, or if they’ve developed an eating disorder.

Who is at risk for the Relative Energy Deficiency in Sports (RED-S)?

Athletes who do a lot of physical activity are at risk for low energy availability due to under eating, over exercising or both. Athletes who are very competitive or focus a large part of their lives on their sport are considered to be at a higher risk. Certain activities that involve a lot of endurance (such as long distance running) may put you at more risk for RED-S. There is also a higher risk among girls involved in activities that demand a thin physical appearance, such as gymnastics or dancing. Being aware of these demands or pressures on your body is a good first step towards keeping yourself healthy. It’s important to remember to balance your sports activities and nutrition. The right balance will keep you healthy.

What is the Relative Energy Deficiency in Sports and what causes it?

Relative Energy Deficiency in Sports (RED-S) is a syndrome (collection of signs and symptoms) that links health problems including: low energy availability with or without disordered eating, menstrual dysfunction, low bone density, cardiovascular and psychological health. The definition was recently expanded to include all athletes, not just those who have periods, though you may still hear the term “Female Athlete Triad” describing this syndrome. However, girls may begin to skip periods if they are not getting adequate nutrition for the amount of exercise they do (energy availability). Periods also may be irregular. Stress lowers estrogen levels, which may cause skipped periods. Low estrogen levels and a lack of menstrual periods can lead to low bone mass (low bone mineral density) and stress fractures (small cracks) in their bones.

Health care providers, athletes, and coaches may continue to use the term “Female Athlete Triad” (triad means three) or the more recent “Relative Energy Deficiency” to refer to athletic girls who have the following:

1. Insufficient nutrition for the level of activity, termed “Low energy availability” (with or without disordered eating):Healthy female athletes get enough calories through the food they eat to provide their body with energy. Unhealthy female athletes do not get enough nutrition (calories/energy). The result can lead to low body weight, irregular menstrual cycles and low bone density that may or may not happen all at the same time. Even eating regular amounts of food may not be enough for a very active person to maintain a normal weight. Healthy nutrition is needed to have regular periods and normal estrogen levels. If you lose weight, you are especially likely to skip periods. Some girls also have an eating disorder such as anorexia nervosa or bulimia. When a young woman with anorexia nervosa or bulimia exercises too much, she is putting an extreme strain on her body.
2. Menstrual Dysfunction: This is defined as the irregular, infrequent, or amenorrhea (no menstrual periods) for longer than 90 days. This lack of menstrual periods can happen when there is significant weight loss, disordered eating, or intense training or exercise. A certain percentage of body fat is needed to maintain a healthy weight and strong bones. Girls will stop having their periods if their weight drops to an unhealthy level for their body, or their nutrition is not balanced. Having your period every 2 to 3 months or very light periods may be a sign that you are not taking in enough nutrients, particularly if you are very active. A healthy weight is especially important for your body to make enough of the female hormone, “estrogen.” Normal levels of estrogen are important for your body to absorb calcium (a mineral your body needs to build strong bones). Low levels of estrogen can cause low bone mass.
3. Low Bone Density: This is when your bones are weaker than they should be. Although physical activity helps to build a healthy skeleton and strong bones, too much exercise can cause problems if you don’t have regular periods and normal estrogen levels. Everyone (teen girls especially) needs the right balance of adequate nutrition, exercise, body weight, calcium intake, vitamin D, and estrogen levels to have healthy bones.

What health problems can RED-S cause in the future?

Each of the above conditions (low energy availability, menstrual dysfunction, and low bone density) are serious conditions that can cause health problems in the future and the need for special medical care. Even if you only have one or two of the conditions, it’s important to talk about them with your health care provider. For example, athletes may eat a healthy diet yet still skip menstrual periods and be at risk of low bone mass.

Disordered eating can cause heart problems such as an irregular heartbeat, muscle weakness or fatigue, fainting, and loss of concentration with school work and athletics.

Menstrual Dysfunction- Irregular/infrequent or no periods are signs that your body is not functioning properly. The biggest concern is that low estrogen levels may result in low bone mass.

The teen years are the most important time in a girl’s life for developing healthy and strong bones for the future.  Most healthy young women will gain most of their bone mass (bone strength) by the time they are 18 years old; however, the peak time for developing healthy bones is between 11 and 14 years of age. This means that by the time you are 20 years old, your bones will likely be the strongest they will be.

During your teen years, low bone mass and intense exercise can make it easier for you to get stress fractures. A stress fracture is a very small crack that can occur in bones when you do the same activity over and over for too long. For example, a runner may get a stress fracture in her lower leg or foot, and a gymnast may get a stress fracture in her spine. If you continue to do the activity in spite of the pain, the bone may break.

How will I know if I have low bone mass?

If you are skipping periods and your health care provider is worried about low bone mass, he/she may suggest that you have a test that can tell whether your bones have lost thickness or strength. One of these tests is called a DXA (Dual Energy X-Ray Absorptiometry) scan. It’s a painless test that uses low radiation waves (multiple x-rays) to take a picture of your bones. The test results allow your health care provider to assess whether you have more or less bone mass compared to other girls your age.

What should I do if I’m a female athlete?

• Give your body enough energy to fuel your performance. During sports seasons, make sure you eat a healthy diet with enough calories to make up for all of your training. Ask your health care provider: What is a healthy weight for you? Try not to lose weight if you are already at a healthy weight. Eat a balance of fats, protein, and carbohydrates. Make sure you get 1300 mg of calcium and at least 600 international units of vitamin D every day (through eating a healthy diet and taking vitamins) to keep your bones strong. Over-the-counter multi-vitamin tablets contain different amounts of vitamin D.
• Keep a menstrual calendar. Use a calendar or phone app to keep track of when your periods start and how long they last. If you’re skipping periods, see your health care provider. It may be a sign that your body is under too much stress, or that you’re not taking in enough nutrients (calories).
• Don’t ignore injuries. If you develop the same pain in your leg or foot every time you run, the same pain in your back whenever you do gymnastics, or the same pain in any part of your body whenever you do the same activity, you may have a stress fracture. Be sure to get it checked out.
• Talk with your health care provider. If you are bingeing, purging, not letting yourself eat, avoiding fats in your meals, or worried about your weight a lot of the time, get help from coaches, trainers, and health care providers. While some problems may be hard to talk about, the earlier they are treated, the better.

Our health guides are developed through a systematic, rigorous process to ensure accuracy, reliability, and trustworthiness. Written and reviewed by experienced healthcare clinicians from Boston Children's Hospital, a Harvard Medical School teaching hospital and consistently ranked as a top hospital by Newsweek and U.S. News & World Report, these guides combine clinical expertise, specialized knowledge, and evidence-based medicine. We also incorporate research and best practices from authoritative sources such as the CDC, NIH, PubMed, top medical journals, and UpToDate.com. Clinical specialists and subject matter experts review and edit each guide, reinforcing our commitment to high-quality, factual, scientifically accurate health information for young people.