Understanding RED-S (Relative Energy Deficiency in Sport)

Distance running places significant demands on the body. Training adaptations only occur when athletes consistently provide their bodies with enough energy to support both exercise and normal growth, development, and recovery. Relative Energy Deficiency in Sport (RED-S) occurs when an athlete does not consume enough energy (food) to meet the combined demands of training and everyday life. While RED-S is sometimes associated with intentional dieting or eating disorders, it is often unintentional. Busy schedules, skipped meals, underestimating calorie needs, or increasing training volume without increasing food intake can all contribute. RED-S affects both female and male athletes and is especially common in endurance sports like distance running. 

The consequences of RED-S extend far beyond simply feeling tired. Athletes may notice declining performance, slower recovery, persistent fatigue, recurring injuries, stress fractures, frequent illness, mood changes, or difficulty adapting to training. While training volume can contribute to fatigue, athletes who are properly fueled generally tolerate training much better. Sometimes what appears to be "overtraining" is actually inadequate fueling. In adolescents, RED-S can also interfere with normal growth and healthy bone development. RED-S is one of the leading preventable risk factors for bone stress injuries in distance runners. The good news is that RED-S is both preventable and treatable. Eating enough throughout the day, fueling before and after workouts, avoiding restrictive dieting, and speaking up early when symptoms appear help athletes stay healthy and perform at their best. Our coaching staff believes that long-term health always comes before short-term performance.

Food is fuel. Eating enough is not a reward for training—it is part of the training. Athletes who consistently meet their energy needs recover faster, stay healthier, suffer fewer injuries, and ultimately perform better over the course of a season and throughout their athletic careers. We place a strong emphasis on proper fueling throughout our program. Proper fueling often requires planning and intentional effort. This might even mean eating when not hungry at times and planning ahead for pre and post run snacks. 

Fueling for a high school distance runner often looks different than what many adults think of as "healthy eating," and this is a tough concept for parents and athletes to grasp at times. Carbohydrates and sugars are NOT the enemy that they have been made out to be and can play a critical role in health and performance when consumed correctly. Please be sure to visit our nutrition page to access resources developed by sports nutrition professionals. 

Growing teenagers who run 25–50 miles per week need a tremendous amount of energy. It is normal—and healthy—for high school distance runners to eat much more than their less active peers. A large appetite is often a sign that an athlete is meeting the demands of training and growth. 

Common Warning Signs for Distance Runners

Parents and athletes are encouraged to discuss these symptoms with a healthcare provider:

• Declining performance despite consistent training

• Persistent fatigue or unusually slow recovery

• Frequent illnesses

• Recurring bone injuries or stress fractures

• Ongoing muscle soreness

• Mood changes or irritability

• Loss of menstrual periods or delayed puberty (girls)

• Significant or unintended weight loss

• Feeling cold frequently or trouble sleeping

How High School Distance Runners Can Help Prevent RED-S

The best way to prevent RED-S is to make sure your body consistently receives enough energy to support both running and normal growth. Consider these healthy habits:

• Eat three balanced meals every day. Skipping meals—even on busy school days—makes it difficult to meet your energy needs.

• Don't skip breakfast. A good breakfast helps replenish energy after an overnight fast and prepares your body for school, practice, and learning.

• Fuel before practice. If practice is after school, have a snack 1–2 hours beforehand, such as a peanut butter sandwich, yogurt and granola, fruit with string cheese, or trail mix.

• Eat within 30–60 minutes after workouts. Recovery nutrition should include both carbohydrates and protein to help muscles repair and replace energy stores.

• Don't be afraid of carbohydrates. Foods like pasta, rice, potatoes, bread, fruit, oatmeal, and cereal are essential fuel for distance runners.

• Hydrate throughout the day. Water should be your primary beverage. During long or hot workouts, sports drinks may also help replace fluids and carbohydrates.

• Avoid restrictive diets or trying to lose weight during the season. Most high school runners perform best when they focus on fueling well rather than eating less.

• Increase your food intake when your training increases. Hard workouts, long runs, training camps, and championship season all require additional fuel.

• Prioritize sleep. Aim for 8–10 hours of sleep each night. Recovery depends on both proper nutrition and adequate rest.

• Pay attention to your body's warning signs. Persistent fatigue, declining performance, frequent illness, recurring injuries, or prolonged muscle soreness are signs that you may not be recovering well.

• Girls should monitor their menstrual health. Missing periods or irregular menstrual cycles should never be considered "normal" for an athlete and should be discussed with a healthcare provider.

• Speak up early. If you're concerned about your energy level, nutrition, recovery, or health, talk with your parents, coach, athletic trainer, physician, or a registered sports dietitian. Early intervention can prevent more serious health problems.

Here are a few resources if your are interested in learning more:

REDs in Sport (International Expert Resource) – A comprehensive educational website developed by international RED-S experts with sections on causes, symptoms, health effects, performance effects, prevention, and treatment. 

For Parents: RED-S in Young Athletes (American Academy of Pediatrics) – Excellent parent-friendly introduction explaining causes, warning signs, prevention, and treatment. 

Awareness of REDs: How to identify REDs in Athletes + What to Do - Slides from a presentation by Morgan Smith (PhD CSCS) at the Wildwood Running clinic in December of 2025. Information is very detailed.

Disclaimer

This information is provided for educational purposes only and is not intended to diagnose, treat, or replace medical advice from a qualified healthcare provider. Every athlete is different. If you have concerns about your athlete's nutrition, energy level, recovery, menstrual health, growth, or overall health, please consult your physician or a registered sports dietitian familiar with working with adolescent athletes.