Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In



Why Underfueling Will Lead to Underperforming

What you should know about relative energy deficiency in sport (RED-S)

Enjoy unlimited access to Climbing’s award-winning features, in-depth interviews, and expert training advice. Subscribe here.

For years, Mina Leslie-Wujastyk was the model of a dedicated climber, pushing herself to the limit on V13 boulder problems and powerful 5.14s. When she broke her wrist in 2019, she opted for one-arm hangboard training and running instead of climbing. However, her dedication had a dark side. She says, “For years, I was treading a thin line between where my body genetically wanted to be and where I thought I needed to be for climbing … I was super tired in what I now realize was an abnormal way.”

Something was off.

Leslie-Wujastyk only discovered that she had Relative Energy Deficiency in Sport (RED-S)—a fundamental mismatch between energy (calorie) consumption and energy output—in 2019 after going off birth control, when her period failed to return. Looking back, she realizes she had probably been in RED-S for about five years. “Symptoms are easier for me [to notice] now that they are gone, actually!” she muses. They included post-pill amenorrhea, low iron levels, frequent urination (two to three times a night), getting sick more often, a lowered libido, insomnia, being “generally more emotional,” and struggling to maintain her weight and gain muscle mass.

What is RED-S?

RED-S evolved from another condition: Female Athlete Triad. This condition was originally identified in female athletes who had low bone-mineral density, menstrual disturbances, and disordered eating. Following decades of research, we now know that the Triad isn’t just a triad—it affects a number of body systems. We also know that it doesn’t just affect females.

In 2014, a landmark position paper put out by the International Olympic Committee introduced the world to the term RED-S. Some within the scientific community pushed back, arguing that there was insufficient research to support pivoting from the Triad to RED-S. However, it’s become clear from the research (see References below) that the term RED-S is warranted and supported. This diagnosis more accurately captures what occurs in the body, and is more inclusive of all genders.

You need calories to maintain body processes like respiration, heart rate, cell-tissue turnover, hormone production, and more. On top of those, you also need energy to think, move, work—and climb. However, if you aren’t eating enough to match these needs, you may create an energy deficit (also called low energy availability). If this happens chronically, such as with dieting or disordered eating, it can lead to RED-S. This can occur within months. Some research suggests that even if the person is eating enough overall calories, going too long between meals may negatively affect menstruation, recovery from training sessions, and bone health. Climbers can be particularly susceptible to RED-S. In a sport where a high strength-to-weight ratio is key and lightness is valued, chasing the next diet can leave you vulnerable, as can overtraining or failing to periodize your training properly (i.e., continuing too long in a given cycle—not integrating both training and rest phases to stay strong and healthy).

As Rebecca McConville, dietitian and author of Finding Your Sweet Spot in Sport: How to Avoid RED-S, told me about both athletes and America at large, “One of the most concerning things I have seen with RED-S is our culture’s ability to normalize underfueling. There seems to always be a fix for the dysfunction rather than preventing the dysfunction from starting.” Leslie-Wujastyk’s experience bears this out, too: “Try not to get into this situation in the first place. It is not worth it and is really hard, mentally and physically, to come back from,” she says. “I’d like to see a future where climbers have more of an array of body types and perform just as well.”

How does RED-S interface with eating disorders?

Eating disorders are a form of mental illness, but if they include a food-restriction component, they may lead to RED-S. However, not all people with RED-S have eating disorders—RED-S can also be the result of inadvertently not eating enough or deliberately dieting to lose weight. Anecdotally, I see this syndrome all the time in my practice. Athletes often are undereating and not fueling their training load. Scientifically, in my research on adolescent climbers, I found that 82 percent of those surveyed were not eating enough to match their caloric needs.

What should I do if I think I have RED-S?

Find a physician or sports physician who is informed in RED-S and athlete treatment, as well as a registered dietitian (look for a Board Certified Specialist in Sports Dietetics, meaning a CSSD credential). If your RED-S overlaps with disordered eating, find a qualified therapist—therapists are a crucial part of an eating-disorder-recovery treatment team. Meanwhile, a sports psychologist can help you cope with anxiety due to lost climbing time. To aid in your recovery, you’ll need to rest and eat more. It also helps to have self-compassion—don’t beat yourself up. Gather a support system of qualified professionals, caring coaches, and friends and family. You’ve got this.

For her part, Leslie-Wujastyk chose to stop exercising in order to recover. She says, “Food and weight gain didn’t seem to change anything alone, but when I also stopped exercise, things really began to feel like they were improving. I got my period back a few months later, and then slowly started to reintroduce exercise.” She is now symptom free and climbing strong again.

A key part of recovery from RED-S is eating enough overall calories. It’s not uncommon to temporarily refrain from exercise as well.Oatmeal Stories / Getty Images

The Damaging Effects of Red-S on the Body

Signs and symptoms

  • Decreased immunity. You may become sick more easily and more often.
  • Reproductive-hormone imbalance. Effects may be low testosterone for males, lost or irregular periods for females.
  • Gastrointestinal disturbances. Effects include food intolerances, bloating, and early satiety—feeling full “too soon” when eating.
  • Increased cardiovascular risk. Sufferers may experience heart-rate irregularities and, in severe cases, heart attacks.
  • Stunted growth and puberty may occur in children and adolescents.
  • Compromised bone health may lead to stress fractures, lost bone-mineral density.
  • Metabolic disturbances can include decreased thyroid hormone, heart rate, and ability to add muscle mass.

RED-S can result in

  • Decreased glycogen stores. Glycogen is the storage form of sugar in muscles and liver; it powers your movements and keeps blood sugar stable.
  • Decreased or plateaued performance.
  • Decreased muscle strength.
  • Decreased coordination.
  • Decreased concentration.
  • Impaired judgment.
  • Mood disturbances may include depression, irritability.
  • Increased risk for injury.
  • Increased fatigue.

Marisa Michael, MSc, RDN, CSSD, is a registered dietitian with a private practice in Portland, Oregon. She is the author of Nutrition for Climbers: Fuel for the Send and a member of the USA Climbing Medical Committee. Find her at and @realnutritiondietitian.