RED-S: The Silent Energy Crisis Destroying Young Athletes From the Inside

She was the best distance runner in her county — lean, disciplined, and relentless. Her coach praised her work ethic. Her parents marveled at her dedication. She trained six days a week, ate "clean," and shaved seconds off her personal bests every month. Then, at sixteen, she fractured her femoral neck during a routine training run. No fall. No contact. Just a bone that had been silently hollowed out from the inside because her body had been running on empty for two years, and nobody noticed because everything looked like success.

Her story is not unusual. It is, in fact, one of the most common and most preventable catastrophes in youth sport. The condition responsible has a name: Relative Energy Deficiency in Sport, or RED-S. It is not a niche diagnosis for elite athletes. It affects adolescents across every sport, every gender, and every competitive level. And the reason it destroys so many young careers is that it hides behind the very behaviors sport culture celebrates most: discipline, leanness, and a willingness to push through pain.

From the Triad to RED-S: Why the Old Framework Was Dangerously Incomplete

For decades, sports medicine recognized a condition called the Female Athlete Triad — a trio of interrelated problems: disordered eating, menstrual dysfunction, and low bone mineral density. The Triad framework, first described by the American College of Sports Medicine in 1992 and updated by De Souza et al. in a 2014 BJSM consensus , was groundbreaking at the time. But it had two critical blind spots: it only described three consequences when the damage is far more widespread, and it implied that only females were affected.

In 2014, the International Olympic Committee introduced the concept of RED-S and published its first consensus statement. The landmark 2023 IOC Consensus Statement on RED-S, led by Mountjoy et al. , represents the most comprehensive update to date. It establishes that low energy availability (LEA) — the root cause of RED-S — impairs virtually every physiological system in the body, and that male athletes are also significantly affected, though the condition often presents differently.

Low Energy Availability: The Engine of Destruction

Energy availability is not the same thing as caloric intake. It is the energy remaining after exercise expenditure is subtracted from dietary intake, relative to fat-free mass. In simple terms, it is the fuel left over for your body to run its basic biological functions — growing bones, producing hormones, fighting infections, repairing tissue, and supporting brain function.

When energy availability drops below approximately 30 kcal per kilogram of fat-free mass per day, the body enters crisis mode. It begins rationing energy by shutting down systems it deems non-essential for immediate survival. Reproductive hormones decline. Bone turnover shifts toward resorption. Metabolic rate drops. The immune system weakens. Growth slows. And critically, the athlete often feels fine — or even feels better, because the initial weight loss and the cortisol-driven alertness of a stressed body can temporarily mimic peak performance.

Low energy availability can arise intentionally — through deliberate calorie restriction or disordered eating — or unintentionally, when a growing adolescent increases training volume without adequately increasing food intake. The latter scenario is alarmingly common in youth sport. A thirteen-year-old who moves from recreational to competitive training may double their energy expenditure overnight while nobody adjusts their nutrition. They aren't trying to lose weight. They simply don't eat enough because no one told them they needed to.

The 10+ Body Systems Under Attack

The 2023 IOC consensus statement identifies the following systems impaired by RED-S. This is not a list of theoretical risks — these are documented, evidence-based consequences:

• Bone health: Reduced bone mineral density, increased bone stress injuries (stress fractures), and impaired bone development during the critical adolescent window when 90% of peak bone mass is established. Athletes with LEA have a 4.5-fold increased risk of bone stress injury.
• Endocrine/reproductive: Suppression of the hypothalamic-pituitary-gonadal axis leads to menstrual dysfunction in females (oligomenorrhea or amenorrhea) and suppressed testosterone in males, with cascading effects on bone, muscle, and mood.
• Metabolic: Reduced resting metabolic rate, impaired glucose metabolism, altered lipid profiles, and metabolic adaptations that make recovery increasingly difficult ...