Athletes Learn to Fuel Better After RED-S Awareness Rises

When top-ranked tennis player Emma Navarro shared her struggle with extreme fatigue, brain fog, and constant hunger on Instagram, she helped shine a light on a condition that's finally getting the attention it deserves.

Relative energy deficiency in sport, or RED-S, happens when athletes don't eat enough to support their training and basic body functions. It sounds simple, but the effects ripple through nearly every system in the body, from bone health to immune function to mental clarity.

The condition isn't limited to elite athletes. Anyone ramping up their gym sessions, training for a first half-marathon, or increasing activity while trying to lose weight can experience it. The key word is "relative"—it's all about not meeting your individual energy needs, whatever they are.

Here's the encouraging part: doctors and sports dietitians are getting better at spotting RED-S early. Simple signs like persistent fatigue, longer recovery times, increased hunger, or mood swings can signal that someone needs to eat more to match their activity level.

Women face higher risk than men, with a 2026 study finding that 70% of high-level female athletes are at risk. Sports that emphasize leanness like running, gymnastics, and diving see particularly high rates. But awareness is changing how coaches, trainers, and athletes approach fueling.

Sports dietitian Amy Stephens notes that while underfueling can show effects after just one day, recovery typically takes six to nine months with proper nutrition. The body is remarkably resilient when given what it needs.

Early warning signs include trouble sleeping, getting sick more often, declining performance, and hair loss. More serious symptoms like missing periods or frequent bone injuries require immediate medical attention, especially for young athletes building peak bone mass during critical growth years.

Why This Inspires

Athletes like Navarro speaking openly about RED-S are breaking down the stigma around fueling properly. Their honesty is helping others recognize symptoms earlier, before long-term damage occurs. Doctors Elizabeth Matzkin and Amy West at Brigham and Women's Hospital and Northwell Orthopedic Institute are leading efforts to educate athletes, coaches, and parents about matching food intake to activity levels—framing proper fueling as a performance advantage, not a weakness.

The message spreading through sports communities is powerful: eating enough isn't just about today's workout, it's about being able to keep doing what you love for years to come.