As an athlete, performance is your top priority. Pushing yourself to run faster, jump higher, and play harder is how you hone your skills and dominate your sport. How you nourish your body directly impacts your strength and endurance, and thus nutrition plays a large role in your training routine. Without adequate fuel, athletes are prone to the unhealthy consequences of burnout and susceptible to a syndrome called Relative Energy Deficiency in Sport, or RED-S. Learn how to lower your risk of developing RED-S with consistent, adequate, balanced nutrition.

What is RED-S?
RED-S is a syndrome that occurs when athletes don’t consume enough energy to support their activity levels. Not eating enough in the short term can cause performance dips, fatigue, muscle cramps, headaches, and moodiness. In the long term, not eating enough will lead to the more serious complications associated with RED-S, including:
- Increased risk of stress fractures
- Early onset osteoporosis
- Amenorrhea or low libido
- Compromised immunity
- Slow metabolism
- Heart damage
- Digestive dysfunction
- Dry, brittle hair, skin, and nails
- Depression, anxiety, and mood disorders
What causes RED-S?
The main cause of RED-S is low-energy availability, or LEA. We expect an athlete’s energy stores to be depleted after a demanding workout, practice, or competition, which is why we recommend they take adequate rest and consume densely nourishing meals. When an athlete doesn’t rest or eat enough, their body is forced to dip into energy and nutrient stores, like muscle, fat, and bone.
It is a myth that a calorie restricted body will burn through fat stores for energy. It’s actually more efficient for the body to break down protein for fuel, compromising the athlete’s muscles, heart and lungs. When nutrient deprived, the body will also break down bone tissue for minerals, which also opens the athlete up to increased risk of injury and fracture.
LEA happens as a result of being in a calorie deficit from either under-eating or overexercising. Sometimes this is unintentional, for example, an athlete who believes that training harder and longer without rest days will make them better at their sport. Other times, athletes might engage in intentional calorie restriction or dieting to alter their physique, for example a runner who has been told by their coach they would be faster if they were thinner, or a swimmer who is concerned about how their body looks in a bathing suit. This can lead to an athlete developing disordered eating or an eating disorder.

Who is most at risk of developing RED-S?
All athletes, regardless of age, race, or background, are at risk of RED-S. This includes everyone from amateur athletes to professionals. However, those that participate in sports that place emphasis on appearance or associate thinness with performance are at greater risk than those who do not, like swimming, gymnastics, or figure skating. Other sports that put emphasis on weigh-ins, like rowing or wrestling, can also put stress on the athlete. Marathon running and cycling are endurance sports that also have high rates of RED-S.
Team culture also plays a large role in an athlete’s RED-S risk. Athletes who are repeatedly subject to commentary about their weight or bullying about their body size are more likely to engage in unsafe eating and exercising practices to alter their body.

The “Female Athlete Triad”
The female athlete triad refers to a subset of athletes with RED-S who experience disordered eating, loss of menstrual cycle, and bone loss. Losing one’s period can have dire health implications through adolescence and adulthood and should not be taken lightly. It’s important to note that any athlete, regardless of gender, is at risk of developing RED-S and suffering from serious health complications.
Symptoms of RED-S
If you are concerned that you or a loved one might be struggling, look for these symptoms:
- Fatigue
- Weight loss
- Missing periods
- Frequent illnesses
- Increased injuries
- Hair loss
- Insomnia
- Brain fog
- Always feeling cold
- Mood swings
- Poor performance
Addressing RED-S as soon as you see potential symptoms increases your chance of a full recovery. Talk with your loved one about what you’ve observed and offer help and support. If you aren’t sure your loved one’s symptoms warrant concern or believe they may be struggling with an eating disorder, schedule a consultation with their doctor, therapist, or a registered dietitian.

Nutrition for athletes to prevent under-fueling
Athletes who do not eat enough to support their energy expenditure are at greatest risk of developing RED-S. That said, let’s take a look at the nutrients that you should include in your training diet:
Carbohydrates:
Carbohydrates are our main energy source! We store carbohydrates as glucose in our muscles and our liver for easy access during training, but these stores are quickly depleted during exercise. That’s why it’s important to include carbohydrates at every meal. Many athletes are surprised to learn that more than 50% of their diet should consist of carbohydrates! Carbohydrate foods include:
- Grain products like oats, cereal, bread, pasta, rice, tortillas, pretzels, crackers
- Starchy vegetables like potatoes, peas, corn
- Fruits like bananas, apples, grapes, berries, citrus (can be fresh, frozen, or dried)
- Fun foods like cookies, donuts, cakes, and more
Proteins:
Protein is what helps our muscles recover after exercise. Protein acts as a building block not just for skeletal muscle, but also for hair, skin, nails, cartilage, bones, and blood cells. Protein should make up 20-30% of the athlete’s diet. It’s important to note that eating more than 20-30% protein does not mean your muscles will grow stronger or faster! Protein in excess of what your body needs will either be used for energy or stored as fat for later. Protein foods include:
- Animal proteins like chicken, turkey, pork, beef, fish, and seafood
- Dairy protein like milk, cheese, Greek yogurt, and cottage cheese
- Plant protein like soy, beans, lentils, seeds, nuts, and nut butters
Fats:
Fats are an often-neglected nutrient in the athlete’s diet. Fat plays an important role in an athlete’s ability to perform endurance sports, as fat stores become an athlete’s main energy source after carbohydrate stores are depleted. In the body, fat is needed for nerve transmission and muscle contraction, as well as absorbing and transporting essential vitamins A, D, E, and K. Fats should make up 20-35% of your total intake. Foods that contain fat include:
- Oils, butter, salad dressings
- Avocados, olives
- Cheese and full fat dairy
- Nuts, nut butters, and seeds

Micronutrient-rich foods:
Fruits and vegetables provide value to the athlete as they contain a variety of vitamins and minerals. Vitamins E and C aid in recovery with their antioxidant properties. Vitamin D and calcium prevent bone degradation and maintain electrolyte balances. Iron supports oxygen transport in your blood to your heart, lungs, and muscles during exercise. Vitamin B12 is needed for healthy nerve tissue and red blood cell formation. And zinc can prevent oxidative damage to your tissues. The list goes on! Some of our favorite micronutrient-dense fruits and vegetables include:
- Kale
- Spinach
- Avocado
- Broccoli
- Brussels sprouts
- Oranges
- Berries
- Carrots
- Bell peppers
- Potatoes
- Bananas
How much does an athlete need to eat?
Every athlete is unique, as are their total energy needs. Eating to hunger may not be enough– many athletes need to eat more than they think to sustain their energy expenditure. If you aren’t sure exactly how much you need to consume, consult with one of our specialized registered dietitians to create a fully custom meal plan that contains all the macro and micro nutrients you need to perform your best.
In general, it can be helpful to think about building a balanced plate that contains carbs, protein, fats, and fruits/vegetables at each meal to ensure you’re eating enough. On training or competition days your total energy needs and total carbohydrate needs will likely increase, so filling up to half of your plate with carbohydrates will be appropriate.
In addition to eating consistent, adequate meals during the day, eating before and after exercise is key to making sure you have enough fuel to perform and recover effectively. Before exercise, consider pairing a carbohydrate with a protein for fast energy. Some of our favorite pre-workout snacks are:
- Banana and peanut butter
- Greek yogurt and granola
- Scrambled eggs and toast
- Milk and cereal
- Oatmeal and almonds
After working out, consider a snack or meal balanced with protein, carbs, and fats. Replenish with these post-workout munchies:
- Pita, hummus, and carrots
- Chicken, rice, and broccoli
- Toast, egg, and avocado
- Turkey and cheese sandwich
- Protein shake made with protein powder, milk, fruit, and nut butter

Where to find more support
Find even more support and learn how to adequately fuel yourself to perform your best by reaching out to one of our dietitians today!
Kristin Jenkins is a dietitian nutritionist based in Maryland. She has been involved in the field of eating disorders and disordered eating for over 6 years and brings both personal and professional experience to her work serving clients who struggle with their relationship with food and their bodies.