If you’re training consistently but feel more exhausted than you think you should, you’re not alone. Maybe your workouts feel harder than they used to, your recovery takes longer, or your performance has stalled despite doing “all the right things.” For some athletes, this also shows up as a missed period, frequent injuries, or feeling run down no matter how well they sleep.

These signs are often brushed off as part of training hard or pushing your limits. But in many cases, they’re signals that your body isn’t getting enough energy to keep up with the demands you’re placing on it. That disconnect between training, fueling, and recovery is at the core of a condition called Relative Energy Deficiency in Sport (RED-S) even if you’ve never heard that term before.

Understanding how RED-S develops and what it looks like is an important step toward feeling better, improving your performance, preserving your sanity, and protecting your long-term health.

What is RED-S?

Relative energy deficiency in sport develops from low energy availability (LEA), which means your body doesn’t have enough energy to support both exercise and everyday bodily functions. (That includes everything from keeping your organs working properly, regulating your body temperature, powering your brain, and supporting all the little movements that make up everyday life.) This can happen intentionally through dieting or food restriction, or unintentionally when your exercise level increases without a matching increase in your food intake.

Over time, inadequate energy intake leads to widespread physical and psychological consequences. Your body prioritizes its own survival over performance, recovery, and hormone health.

How relative energy deficiency in sport affects the body

RED-S is a multisystem condition. Chronic low energy availability can disrupt nearly every system in the body, including:

• Metabolic: Reduced resting metabolic rate (AKA, the amount of calories you burn just by existing)
• Reproductive: Menstrual irregularities or loss of your period; suppressed testosterone
• Bone health: Decreased bone mineral density, increased stress fracture risk, and increased risk of osteoporosis or osteopenia down the line
• Cardiovascular: Low resting heart rate and impaired cardiac function
• Gastrointestinal: Bloating, constipation, and delayed gastric emptying
• Immune: Increased illness and slower recovery
• Psychological: Anxiety, depression, irritability, and preoccupation with food
• Endocrine: Disrupted thyroid hormones and cortisol dysregulation

RED-S and athletic performance

The relationship between RED-S and performance can be misleading. Some athletes initially notice performance improvements with weight loss or restrictive eating. These changes are almost always short-lived.

Over time, relative energy deficiency in sport commonly leads to:

• Decreased endurance and strength
• Impaired coordination and focus
• Longer recovery times
• Increased injury risk
• Plateaus or declines in performance

In other words, chronic under-fueling eventually undermines the very performance goals athletes are working toward. Many athletes with RED-S feel like they’re training harder but progressing less, which can lead to even more restriction or overtraining. That cycle deepens energy deficiency and accelerates both physical and mental consequences.

Sustainable athletic performance depends on eating enough, hydrating properly, and giving your body the chance to recover between training sessions or events. Meeting energy needs isn’t a barrier to success — it’s the foundation for adaptation, resilience, and longevity in sport.

Recognizing the risks, signs, and symptoms

RED-S can affect athletes in any sport, but higher-risk groups often include:

• Endurance athletes
• Aesthetic or weight-class sports like gymnastics, dance, wrestling, or rowing
• Athletes with high training volumes
• Individuals exposed to diet culture or weight-based performance messaging
• Athletes with a history of disordered eating or eating disorders

That said, no athlete is immune. RED-S can develop any time energy intake doesn’t adequately support energy output.

Common signs of RED-S include:

• Persistent fatigue or feeling unusually drained after workouts
• Frequent injuries or stress fractures
• Cold intolerance
• Difficulty concentrating
• Mood changes
• Loss of the menstrual cycle
• GI discomfort
• Declining performance despite increased training

Many athletes experiencing these symptoms don’t realize they may be connected or assume they’re just part of training hard.

Why RED-S symptoms are often normalized

One of the biggest challenges with RED-S is that many of its warning signs are normalized, rewarded, or even praised in sport culture. Athletes are often taught that exhaustion, pain, and sacrifice signal commitment or mental toughness.

Common examples include:

• Chronic fatigue being framed as dedication
• A lost period (also called hypothalamic amenorrhea) being seen as normal or even desirable in some sports cultures
• Injuries blamed on bad luck rather than cumulative under-fueling
• GI symptoms dismissed as “just part of being an athlete”
• Mood changes or food fixation seen as discipline

In many environments, athletes learn to distrust their bodies and push through symptoms instead of responding to them. Coaches and teammates may unintentionally reinforce this mindset by prioritizing output over recovery or equating a certain body type with performance.

When RED-S symptoms are treated as normal, athletes often delay care until the condition becomes more severe. Recognizing RED-S requires not just clinical awareness, but a cultural shift that defines strength as fueling adequately, honoring recovery, and responding early when something feels off.

Treatment and recovery from RED-S

The foundation of RED-S treatment is restoring adequate energy availability. This usually means increasing overall energy intake and, when needed, reducing training volume or intensity.

Recovery also includes addressing the psychological side of under-fueling, such as fear foods, rigid food rules, diet culture beliefs, and body trust concerns. When these pieces are addressed together, athletes can support both long-term health and athletic performance.

With proper fueling, recovery, and support, it’s possible to restore hormonal health, improve energy, reduce injury risk, and return to training in a way that’s sustainable and effective.

If you’re struggling with RED-S, a lost period (AKA hypothalamic amenorrhea), or low energy levels, we can help! We’re a group of dietitians who take a non-diet, body-positive, identity-affirming approach to recovery and healing your relationship with food. Go here to learn more about nutrition counseling for kids, teenagers, and adults, in-network with most major insurance companies and offered virtually to clients in North Carolina and over a dozen other states.

Ready to book an appointment? Click here to book online.

Not ready to commit to counseling but want more information about the anti-diet approach? Subscribe to our weekly newsletter.

You might also like:

Why Are Carbohydrates Important? According to a Dietitian.

Feeling Shame About Your Body? Here’s How to Handle it.

The Problem With Fake “Empowerment” in Wellness Culture

The 75 Hard Challenge is Full of Red Flag