By: Lauren Gadek & Sigrid Wolf, MD, FAAP
Relative Energy Deficiency in Sport (RED-S) happens when an athlete does not eat enough nutritious food to meet the energy needs of their sport and their growing body.
RED-S can affect any athlete, regardless of gender, age or level of competition. If it is not recognized and treated early, RED-S can lead to poorer sports performance, more injuries and long-term health concerns. Here's what families need to know about the condition, including causes, symptoms and ways to help prevent and treat it.
Why nutrition is so important for young athletes
Food is more than just calories—it is fuel. Athletes need energy to:
When energy needs are not met, the body starts to conserve fuel by slowing down important systems. This is what leads to RED-S.
What causes RED-S?
RED-S is caused by low energy availability, meaning the athlete is burning more energy than they take in from food.
Low energy availability can happen:
Accidentally, when busy schedules, missed meals or underestimating calorie needs lead to eating too little
Intentionally, when athletes try to control weight, body shape or appearance
Athletes at higher risk for low energy availability include those in:
Weight‑class sports (wrestling, martial arts)
Appearance‑based sports (gymnastics, dance, figure skating)
Endurance sports (running, cycling, swimming)
Signs and symptoms of RED-S
RED-S can show up in many ways. Families should talk with their health care provider if they notice these possible signs and symptoms in a young athlete:
Drop in sports performance, stamina or strength
Needing more time to recover after practices or games
Feeling more tired than usual
Little improvement despite hard training
Trouble concentrating or staying focused
Low motivation or loss of interest in sport
Mood changes, irritability or sadness
Getting sick more often
Repeated injuries, stress fractures or broken bones
Poor sleep
Weight loss or poor weight gain
Irregular or missed menstrual periods
Slowed growth or delayed development
Effects of RED-S on a young athlete's body
Sports performance
Without enough fuel, the body cannot work as efficiently. Athletes may feel weaker, less coordinated or have trouble concentrating. Over time, injuries become more likely, and training results may stall or decline.
Bone health
Puberty is an important time for building strong bones. Hormones like estrogen and testosterone help bones grow and stay sturdy. Low energy availability lowers these hormone levels, which can weaken bones and increase the risk of stress fractures and broken bones—now and later in life.
Growth and development
RED-S may cause athletes to grow more slowly, have poor weight gain or even weight loss. Families should talk to their child's health care provider if they notice changes in the athlete's growth. It is important to determine if stunted growth and development is due to RED-S, disordered eating, lack of access to healthy food or other causes.
Puberty and reproductive health
During puberty, kids' bodies go through a major growth spurt. That takes a lot of energy. When a child isn't getting enough fuel from food, it can affect puberty:
- For girls, this may show up as irregular or missed periods. Some uneven timing is common in the first year or two after periods start, but gaps longer than three months (90 days) are not considered normal and should be checked by a health care provider.
- For boys, signs can include delayed puberty, little or no body or facial hair, or fewer erections. These changes can be a signal that the body doesn't have enough energy to support healthy growth and development.
How RED-S can be prevented
Prevention starts with consistent, adequate nutrition. A supportive team environment goes a long way in protecting young athletes.
Strategies to help prevent RED-S include:
Regular meals and snacks throughout the day
Eating enough to support both training and growth
Viewing food as fuel, not something to restrict
Parents and coaches can help by:
Reducing pressure around weight and appearance
Avoiding harmful messages about dieting
Promoting positive body image and confidence
Focusing on health, strength, enjoyment and performance
How RED-S is treated
Early treatment for RED-S improves both short‑term performance and long‑term health.
Treatment for RED-S focuses on restoring healthy energy balance. This may include:
Increasing calorie intake
Improving meal and snack timing
Adjusting training intensity or volume
Addressing stress, anxiety or disordered eating patterns
Care often involves a team, which may include:
Supporting bone health during recovery
Because most bone strength is built during puberty, treating RED-S early is important. Getting enough calories, as well as calcium and vitamin D, help bones recover. With improved fueling, bones can regain strength over time.
When to reach out for help
Sometimes concerns are not obvious. These questions can help parents decide when to talk with a health care provider.
You might consider reaching out if you've noticed your child thinking or talking about things like:
Body weight and pressure
Feeling unhappy with their weight
Feeling pressure from sport, peers or coaches to gain or lose weight
Worrying a lot about gaining weight during the off‑season or when injured
Food and eating habits
Following strict food rules or special diets
Feeling anxious or guilty about eating
Avoiding certain foods or food groups
Past or current struggles with disordered eating
Food allergies or intolerances that limit intake
Training and injuries
Training extra outside of team practices to lose weight
Having frequent injuries or stress fractures
Missing part or all of a season due to injury
Concerning weight‑control behaviors
Remember
RED-S can impact sports performance, injury risk, growth and long‑term health. Parents, coaches and health care providers all play a role in prevention and early care.
By encouraging healthy fueling, positive body image and balanced training, families can help young athletes stay strong, healthy and confident—both on and off the field.
If something doesn't feel right, trust your instincts and talk with your child's health care provider. Early support makes a meaningful difference.
More information
About Lauren Gadek Lauren Gadek is a medical Student at Northwestern University Feinberg School of Medicine. She is a member of AAP Section on Pediatric Trainees (SOPT), Council of Sports Medicine and Fitness (COSMF), and Section on Endocrinology (SOEn).
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About Dr. Wolf Sigrid Wolf, MD, FAAP, is a member of the AAP Executive Committee on Sports Medicine and Fitness. She is a pediatric sports medicine physician at Ann & Robert H. Lurie Children's Hospital of Chicago and is an associate professor of pediatrics at Northwestern University Feinberg School of Medicine.
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