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What To Know About Relative Energy Deficiency in Sport


As a division 1 cross-country and track runner at the University of Michigan, Erin Finn became an NCAA All-American and Big Ten Champion. But multiple injuries slowed her down, and at a certain point, her body stopped responding well to training. By the time she learned it was because she wasn’t eating or resting enough, which had led to a syndrome called Relative Energy Deficiency in Sport (REDs, and formerly RED-S), it was too late. Looking back, she wonders what more she could have achieved as a runner if she had been fueling properly.

“My career might have looked very different if I had been able to internalize these concepts earlier,” she says. “I suffered many injuries, and probably have lifelong consequences with bone density that I’m working on fixing.” Now a medical resident, Finn started an educational resource and virtual community called Out of the RED-S to help other athletes avoid the same fate.

What is REDs?

REDs happens when athletes don’t eat enough to fuel their bodies. At the center of this syndrome is low energy availability1: Essentially, if you’re not taking in enough food, your body will use up your calories on exercise, leaving you without enough left in the tank to support your day-to-day bodily functions—and leading to a cascade of health problems.

It doesn’t take much of a deficit to happen. REDs-related dysfunction can start to set in when the body has 250 calories less than what it needs daily, over a five-day period, says sports dietitian Rebecca McConville, RD, LD, CSSD, CEDS, who wrote the book Finding Your Sweet Spot: How to Avoid RED-S by Optimizing Your Energy Balance. “That can kind of start a cascade—if we don’t put the brakes on early, then we start to see long-term consequences of REDs,” she says.

This problem was once considered the “female athlete triad2”—low energy availability, menstrual dysfunction, and low bone mass. But in 2014, the International Olympic Committee (IOC) recognized it as a broader syndrome that can affect people of any gender, and can cause many additional effects: impaired gastrointestinal, cardiovascular, and neurocognitive function, as well as reduced immunity, increased injury risk, and mental health issues, among other problems.

It can also backfire on athletes’ performance through decreased muscle strength, endurance, power, training response, recovery, and motivation, according to a new consensus statement3 released by the IOC last month. Ironically, athletes may respond to this downturn by training even harder, which can deplete even more of the energy they need to function.

Healthcare providers look at several criteria to diagnose REDs, though the IOC statement points out diagnosing it has been inconsistent. “As a dietitian, we can assess where their energy status is. A medical provider can assess their physiological functioning. If dysfunction is noted and they are in a low energy availability, they are generally diagnosed with REDs,” McConville says.

Despite growing awareness, misconceptions persist

In the last several years, awareness of REDs has grown significantly among athletes at all levels, says McConville. This is likely thanks to the fact that several high-profile athletes have spoken out about their struggles with REDs, and created networks and campaigns to raise recognition and provide resources.

But the overall population remains unfamiliar with the syndrome, and some misperceptions persist, like that REDs affects only elite athletes, underweight athletes, or those with disordered eating. In reality, McConville says REDs is likely to be pretty common among recreational athletes—and maybe even more prevalent than in professional sports since everyday people don’t have the same coaching or medical support available. Because it’s not always intentional: We may not even realize how much energy we’re burning up in our workouts, creating a deficit without being aware of it.

Estimates of REDs prevalence vary widely, from 23 to 79.5 percent in female athletes and from 15 to 70 percent for male athletes, according to the IOC statement, which drew from studies that mostly (but not exclusively) focused on elite athletes. McConville says it’s probably on the higher end of that range, more like 65 to 80 percent, because so many cases of REDs are overlooked.

“Some of my most underfueled athletes have been ones that were [at a healthy weight], and so they were overlooked for years,” she says. Sometimes athletes with REDs don’t lose weight at all—instead, the primary symptoms have to do with missed menstrual cycles, or their digestion, or their sleep is a mess, McConville says.

This influence of diet culture

When Finn decided to start Out of the RED-S, she says, “I saw a problem that was unaddressed, that was very, very common.” One major contributing factor is clearly diet culture, and how much of the messaging around fitness and healthy eating is focused on weight loss. “The dialogue and the culture around fueling to perform, versus even fueling for general health, is so radically different than fueling for weight loss,” Finn says.

McConville agrees, noting that “our weight-focused, diet-centered culture” has gotten in the way of more widespread understanding of REDs. “It’s a little bit too normalized, especially in some of these boutique-type gyms that really promote constantly being in a caloric deficit,” she says.

When athletes prioritize losing weight—believing that lighter is faster or that they need to look like the stereotypical star in their sport—they may put their health at risk. REDs is most common in endurance sports, like running and cycling, that require athletes to expend a lot of energy in workouts; sports that idealize thin body types, like figure skating and gymnastics; and sports with weight categories, like lightweight rowing and wrestling.

“Many sports have engrained cultures where coaches and members of the athlete health and performance team exert subtle to extreme pressure on athletes to regulate body weight and composition,” the IOC statement says. Yet many of these people lack knowledge about how to go about doing that safely, it adds.

“A well-fed body is a resilient body.” —Rebecca McConville, RD

Even in healthcare, REDs may not be fully appreciated. “Because healthcare is under so much time constraint, they tend to not put puzzle pieces together,” McConville says. For example, if a patient comes in with GI issues, the healthcare provider may focus only on that, “and they don’t really have enough time to assess energy availability, carbohydrate availability, sleep”—things that indicate REDs may be the cause, she says.

Also, Finn says, “the majority of the healthcare world is focused on obesity, inactivity, and metabolic/insulin resistance,” and these patients’ needs are completely different from those of athletes with REDs.

“Another issue is that medicine is swept up in that same diet culture as the exercise world, [which] sees being thin and eating less and exercising more as being healthier,” Finn says. It’s well-documented that doctors all too often focus on weight when they’re caring for patients in larger bodies. And on the flip side, if a patient comes in with REDs symptoms but is otherwise healthy and thin, their symptoms may not seem like cause for concern.

The path forward

So what can be done? Treatment for REDs involves eating more food. But sometimes that’s more complicated than it sounds. “It’s like an interest on a credit card, when you’ve been in that energy deficit, so you have to make that up first—then you work on figuring out where they’re at that place of proper energy availability,” McConville says. Depending on how long the person has had REDs, the body can be “pretty volatile for about a year,” she says.

Healing can also require a mindset shift. Finn points out that a well-informed coach and team are essential in building accountability “about regularly getting enough fuel or regularly eating breakfast before you work out, or regularly taking a rest day.” And enjoying it.

McConville says, “We really have to start having some institutional culture changes.” This includes the language used on teams, such as body-positive communication that focuses more on what the athlete’s body can do than what it looks like, she says.

Athletes shouldn’t accept these REDs symptoms as normal. “When I think about the athletes sitting across from me, it’s like they settle for dysfunction,” McConville says. “A well-fed body is a resilient body that won’t have all these issues when it’s taken care of.”

Well+Good articles reference scientific, reliable, recent, robust studies to back up the information we share. You can trust us along your wellness journey.

  1. Wasserfurth, Paulina et al. “Reasons for and Consequences of Low Energy Availability in Female and Male Athletes: Social Environment, Adaptations, and Prevention.” Sports medicine – open vol. 6,1 44. 10 Sep. 2020, doi:10.1186/s40798-020-00275-6
  2. Nazem, Taraneh Gharib, and Kathryn E Ackerman. “The female athlete triad.” Sports health vol. 4,4 (2012): 302-11. doi:10.1177/1941738112439685
  3. Mountjoy, M., et al. ‘Et Al2023 International Olympic Committee’s (IOC) Consensus Statement on Relative Energy Deficiency in Sport’. REDs)British Journal of Sports Medicine, vol. 57, 2023, pp. 1073–1097.

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