A fitness term almost nobody could spell five years ago is now showing up in locker rooms across every sport, from distance running to volleyball to weightlifting.
Quick Take
- Relative Energy Deficiency in Sport, or RED-S, happens when athletes burn more calories than they eat relative to their body needs.
- The International Olympic Committee (IOC) says RED-S can damage metabolism, bones, immunity, and heart health, not just menstrual cycles.
- Large reviews of existing studies put low energy availability in roughly 45 percent of athletes tested, with some sports far higher.
- Doctors link rising awareness to extreme training culture, but no study yet proves that culture alone is driving more cases.
What RED-S Actually Means For An Athlete’s Body
The IOC first separated RED-S from the older “female athlete triad” model in 2014, then expanded the science in its 2018 consensus statement. That document describes RED-S as impaired body function caused by eating too little fuel for the amount of exercise an athlete does. The damage is not limited to one gender or one symptom. It can hit metabolism, bone strength, immune defenses, protein repair, and heart function all at once.
Sports medicine specialists describe the math in plain terms. Energy availability equals what an athlete eats, minus what they burn exercising, divided by their lean body mass. When that number stays too low for too long, the body starts shutting down “non-essential” functions to survive, including reproductive hormones and bone rebuilding. Physicians interviewed in recent clinical discussions, including sports medicine and nutrition specialists, describe this as the body protecting itself at a steep long-term cost.
How Common Is This Across Different Sports
Numbers from recent research reviews are striking. A 2024 systematic review and meta-analysis covering 59 studies found low energy availability in 2,737 of 6,118 athletes, or 44.7 percent overall, split almost evenly between men at 49.4 percent and women at 44.2 percent. Another review found RED-S risk reached 63 percent among 730 athletes across eight separate studies, with especially high rates in weight-class and endurance sports.
A separate survey of 192 national-level athletes found that 67.2 percent fell into the medium or high RED-S risk category, with weight-class and intermittent sports showing the steepest numbers. These are not fringe findings buried in one lab. They come from reviews pulling together decades of data across male and female athletes, youth and elite competitors, and sports as different as rowing, wrestling, and figure skating.
Why “Hustle Culture” Is Getting Blamed
Public conversation has started pointing fingers at modern fitness culture, the “no days off” mindset that treats rest as weakness and punishes any day without a workout. Coverage has also raised GLP-1 (glucagon-like peptide-1) weight-loss drugs as a possible factor, since appetite suppression can quietly push athletes into calorie deficits they never intended to create. That link makes intuitive sense, but no published study has yet measured whether hustle culture or these drugs are actually causing more RED-S cases. The timing lines up. Proof of cause does not exist yet.
Screening Tools Are Catching Up To The Problem
The IOC has pushed past simply naming the syndrome. Its REDs Clinical Assessment Tool, now in its second version, sorts athletes into a traffic-light system using objective markers like bone density alongside self-reported symptoms. That gives coaches and doctors a structured way to flag risk before an injury forces the issue, rather than waiting for a stress fracture to show up on an X-ray.
Adoption of that screening tool still varies widely from one team, school, or national federation to the next, which means plenty of at-risk athletes are not being screened at all. For parents of teen athletes and weekend warriors chasing personal bests, the takeaway is simple. Fueling the body properly is not optional, and treating hunger or fatigue as a sign of weakness is exactly the mindset that put this condition on the map.
Sources:
menshealth.com, olympics.com, ssns.ch, link.springer.com
