RED-S: What’s that? (and what you should know and why you should care)

Posted on 13-03-2022 , by: Nancy Clark , in , , , 0 Comments

RED-S stands for Relative Energy Deficiency in Sport. It happens when athletes eat insufficient food relative to the number of calories they burn. Athletes who enjoy the See Food Diet (they see food and eat it) are less likely to experience RED-S compared to those who eat restrictively because they are fearful of weight gain. Athletes who eat only “healthy” foods can also slide into RED-S when they unknowingly consume too few calories to support optimal physiological functions.

Athletes most at risk for RED-S tend to be in sports that
1) emphasize appearance (figure skating, dancing),
2) have weight categories (wrestling, rowing). and
3) require endurance (running, cycling).
But any athlete can suffer from RED-S—even those who have not lost weight. Take note: under-eating is not always accompanied by weight loss! When the body perceives a “famine” (too little fuel), it does an amazing job of preserving itself from wasting away.

I get concerned about RED-S when I hear athletes say things like:
“My friends tell me I eat like a bird…”
“I’m not losing weight, despite all my exercise. Am I eating too much—or too little?”
“I stopped getting my period last year. My doctor said that’s normal for female athletes.”

As mentioned above, RED-S is common in weight-class sports. Case in point: A survey of male and female competitive lightweight rowers indicates that many of the rowers had RED-S. They ate an inadequate amount of food relative to what their bodies deserved to be fed. They prioritized weight over health to qualify to row. As a result, the under-eaters experienced excessive fatigue, muscle loss, poor recovery between training sessions, stress fractures, and reoccurring injuries.

Interviews with the rowers indicate they knew very little about RED-S. Most of the rowers—as well as their health care providers—thought RED-S affected only women who had stopped having regular menstrual periods. Wrong. RED-S applies to both male and female athletes!!! Because lack of RED-S education can easily contribute to long-term health issues, this article educates all athletes, males and females alike, about the adverse effects of being under-fueled. Please share this with your partners, teammates, and others whom you may notice “eating like a bird.”

• A tell-tale sign of RED-S in males is loss of libido/sex drive, and in females, irregular or no monthly menstrual period. Other health issues related to RED-S include weight loss (bot not always), reduced bone health that shows up as stress fractures today and osteoporosis in the future, chronic fatigue due to poorly fueled muscles, nagging injuries, moodiness, and depression. Performance issues include the inability to gain or build muscle or strength, reduced agility and coordination, poor recovery from hard workouts, impaired judgment, loss of mental sharpness, and reduced ability to focus. An athlete’s plan to lose weight to enhance performance commonly backfires in the long run, if not the short term.

• As mentioned above, RED-S appears in not only athletes who consciously restrict their food intake, but also in those who unknowingly consume inadequate fuel to support their bodies’ energy needs. This can happen with athletes who juggle school, work, family, friends, and training demands—and have “no time” to eat. RED-S can also happen with others whose “healthy diet” includes a lot of high fiber foods such as beans, nuts, and whole grains that can curb one’s appetite. Or maybe the athletes think they are eating enough because they eat large portions—but the foods are what I call “fluff” (rice cakes, popcorn, lettuce). Regardless of the cause, having low energy availability affects all systems of the body.

• While restricting food and prioritizing weight over health has become normalized among athletes, you need to know that under-eating is not harmless. Living with an energy deficit affects every system in the body, including the gastrointestinal system (reduced GI motility, constipation), cardiovascular system (dangerously low heart rate, unusual fatigue), slowed metabolism (energy conservation, cold hands, cold feet). An athlete should never try to maintain a “competitive weight” all year round.

• Poor knowledge of RED-S can lead to under-diagnosis, poor management, and poor health outcomes. For example, some health care providers still tell female athletes that amenorrhea is normal in women who train hard. The recommendation to “Just take a birth control pill to get your period” is outdated and does not resolve the underlying problem: an inadequate amount of fuel to support the normal functioning of the whole body.

Do you have RED-S?
Here are a few questions that could help identify if you are under-eating. Do you:
• Constantly think about your food, weight, or body image?
• Severely limit your food intake?
• Experience guilt or shame around eating “unhealthy foods”?
• Count calories or fat grams whenever you eat or drink?
• Feel fat even though others tell you that you are thin?

What’s the solution?
If you are training hard and eating very little, you could easily be experiencing RED-S. While the obvious answer is Just eat more and exercise less, doing so can be difficult. Fear of weight gain is a huge barrier. As I repeatedly hear from my doubting clients, “What makes you think I could eat more, exercise less, and not get fat? That just doesn’t make sense.”

Well, it does make sense because the body does an amazing job of conserving energy (cold hands and feet, low heart rate, loss of menses/libido). When you eat more, your metabolism perks up and you burn off the added calories (as opposed to storing them as excess flab). You’ll then be able to train better, recover better, and perform better. If you are under-eating, start by adding 100 to 300 calories to breakfast, then lunch, and then afternoon snack. Notice the benefits: feeling perkier and well-fueled!

The time is right to revolutionize the culture of sport so that athletes can focus more on performance and health, and less on weight. To initiate this change, you might want to participate in your sport at a weight that fits your genetic physique and allows you to prioritize health over weight. Excelling as a strong and powerful athlete could easily lead to a more satisfying sports career than starving yourself to be an injury-prone athlete who spends too much time sitting on the sidelines. The thinnest athlete is unlikely the best athlete. The best-fueled athlete who is genetically gifted will win the prize!

The bottom line: If you think you have RED-S, talk with a trusted sport dietitian (RD). Poorly managed RED-S can too easily end up as malnutrition, disordered eating, osteoporosis—and a disappointing future for your athletic aspirations.

References: Insufficient knowledge and inappropriate physiotherapy management of Relative Energy Deficiency in Sport (RED-S) in lightweight rowers
Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities

Nancy Clark MS RD CSSD counsels both fitness exercisers and competitive athletes in the Boston-area (Newton; 617-795-1875). Her best-selling Sports Nutrition Guidebook is a popular resource, as is her online workshop. Visit for info.

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