Relative energy deficiency in sport.

If you’re an athlete regularly experiencing fatigue, stress fractures, or decreased endurance, relative energy deficiency in sport, or RED-S, may be the culprit.

RED-S is low energy availability, or an energy imbalance created when an active person fails to meet the caloric intake required to match their level of physical activity.

Simply put, RED-S can develop when your body uses more energy than it gets through diet.

When left untreated, RED-S can negatively impact bone health, menstrual function, immunity, and cardiovascular, psychological, and gastrointestinal health. It can disrupt menstruation, increase the risk of fractures, and reduce the body’s ability to fight illness.

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Previously known as the “female athlete triad,” the condition was renamed by the International Olympic Committee in 2014 to reflect that it affects all genders.

“In some cases, we see decreased menstrual periods, stress fractures, and mental health concerns like eating disorders,” says Kelley Anderson, DO, a primary care sports medicine physician with UPMC Sports Medicine. “Although it may be a component, RED-S is not always associated with an eating disorder; it could be that people don’t have the knowledge of what their energy intake should be. It’s more often seen in athletes in appearance-based sports like gymnastics, ice skating, wrestling, ballet, or weight-category sports. We also see it in endurance sports like track and cross-country.”

Symptoms that may indicate an athlete has RED-S include:

  • Decreased endurance or muscle strength.
  • Frequent injuries, especially stress fractures.
  • Slower recovery times.
  • Menstrual cycle dysfunction, or an absence of menstruation.
  • Delayed growth and development in children, teens, and young adults.
  • Dramatic weight loss, or changes to appearance resembling vitamin or mineral deficiency.
  • Decreased training response.
  • Depression, anxiety, and irritability.
  • Decreased concentration and/or coordination.
  • Fatigue and brain fog.
  • Impaired judgment.

Every body is different, says Dr. Anderson, and the nutritional needs of athletes and other physically active people vary by activity level and body composition.

“It’s really based on the individual,” she says. “So, we recommend meeting with sports nutritionists to determine need. When we suspect RED-S — for example if someone comes to us with a stress fracture or changes to their menstrual cycle — we often order labs looking at levels of iron, vitamin B12, vitamin D, and others to take a multisystem approach.”

That approach at UPMC Sports Medicine includes a team of sports medicine physicians and nutritionists, athletic trainers, and mental health professionals, as needed.

Specialists work with patients to develop individualized meal plans, nutrition coaching, and training modifications to correct the relative energy deficit, and mental health professionals address any related conditions.

“You want to make sure you’re addressing all of those areas, because psychological health in our athletes is something we’re really zeroing in on,” says Dr. Anderson. “With RED-S, it takes a group approach.”

The length of treatment for RED-S can span months to years, she says.

“It depends on the significance of the RED-S, how long they’ve been dealing with it, and how impacted their system is,” she says. “It could be that the energy availability wasn’t too far off, you’ve met with a sports nutritionist, and you’re correcting all of these areas by adjusting your diet and moving forward.”

“Then there are treatment plans that are more longstanding and, say, menstrual cycles have been affected,” Dr. Anderson continues. “We’re following them over six months to a year or longer to make sure that function returns to normal. We may be checking labs every three months for iron levels to see those changes over time. We may even follow student athletes for the duration of their college careers.”

Relative energy deficiency doesn’t only affect traditional athletes, says Dr. Anderson. People who are very physically active, such as runners and endurance trainers, may experience it if their diet doesn’t match the intensity of their exercise regimen.

The key is knowing the signs and addressing those concerns with a health professional, she says.

“When someone realizes they’re not performing their best, they’re having stress fractures, menstrual abnormalities, or they don’t feel like they have enough energy to perform, they should say ‘hey, my system isn’t where it needs to be. I should get evaluated for energy deficiency,'” says Dr. Anderson.

Editor's Note: This article was originally published on , and was last reviewed on .

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