RED-S: Signs, Symptoms & Nutrition Support for Athletes
Athletes are often encouraged to push harder, train longer, and pay close attention to what they eat. But when an athlete isn't getting enough energy to support both their training and their body's everyday needs, performance isn't the only thing that can suffer.
Relative Energy Deficiency in Sport, commonly called RED-S or “REDs”, is a condition that can develop when the body doesn't have enough available energy to adequately support exercise, recovery, and normal physiological functioning. And despite some common misconceptions, RED-S doesn't have a "look." It can affect athletes of different genders, body sizes, ages, abilities, and levels of competition.
At CV Wellbeing, we work with athletes experiencing RED-S, low energy availability, disordered eating, eating disorders, and challenges with adequately fueling for sport. Our goal isn't simply to get someone "back to performance,” but to help athletes build a way of fueling that supports their health, their sport, and their relationship with food.
What is RED-S?
Relative Energy Deficiency in Sport results from chronically low energy availability. Energy availability refers to the energy your body has left to carry out its normal functions after accounting for the energy used during exercise and training.
Your body needs energy for far more than simply movement. Energy is also required to:
Maintain bone health
Produce hormones
Support immune function
Regulate body temperature
Maintain cardiovascular health
Repair and build muscle
Support digestion
Concentrate, think, and learn
Recover between training sessions
Support growth and development
When there isn't enough energy available to meet all of those demands over time, the body may begin conserving energy and changing how certain systems function.
The International Olympic Committee defines RED-S as a syndrome involving impaired physiological and/or psychological functioning caused by prolonged or severe low energy availability. RED-S can affect reproductive function, musculoskeletal health, metabolism, immunity, cardiovascular health, blood health, and athletic performance.
In other words, underfueling doesn't just affect your workout, but your whole body.
What Causes Low Energy Availability?
Sometimes people assume RED-S only occurs when an athlete has an eating disorder or is intentionally restricting food. But that's not always the case. Low energy availability can develop intentionally or unintentionally.
An athlete might not be eating enough because they are:
Trying to lose weight or change their body composition
Following restrictive nutrition advice
Cutting out foods or entire food groups
Experiencing an eating disorder or disordered eating
Afraid that eating more will negatively affect performance
But it can also happen when an athlete has no intention of restricting food.
For example, an athlete might:
Increase their training volume without increasing their food intake
Have a packed school, work, or practice schedule that makes eating consistently difficult
Have limited hunger cues
Take medication that decreases appetite
Have gastrointestinal symptoms that make eating uncomfortable
Have sensory differences that limit available foods
Underestimate how much energy their sport requires
Have limited access to food
Have difficulty eating before or after practices
Believe that feeling hungry, exhausted, or sore all the time is simply part of being an athlete
This is one reason RED-S can be difficult to recognize. An athlete can genuinely feel like they're eating "a lot" and still not be meeting their body's needs.
What Are the Signs and Symptoms of RED-S?
RED-S doesn't always show up dramatically. Sometimes the first signs look like things athletes have been taught to accept as normal: feeling tired all the time, getting injured frequently, struggling to recover, or watching performance unexpectedly decline.
Possible signs of low energy availability and RED-S can include:
Persistent fatigue
Declining athletic performance
Difficulty recovering between workouts
Recurrent injuries
Bone stress injuries or stress fractures
Frequent illness
Changes in menstrual cycles, including irregular or missing periods
Changes in libido or reproductive hormones
Difficulty concentrating
Feeling cold frequently
Changes in mood
Sleep disturbances
Gastrointestinal symptoms
Decreased strength or endurance
Difficulty building or maintaining muscle
Increased preoccupation with food, weight, or exercise
Anxiety about rest days or changes in training
Feeling unusually hungry or experiencing episodes of intense hunger
Not every athlete with RED-S will experience every symptom. The effects can also vary based on factors including age, sex, training demands, duration of low energy availability, genetics, and the degree of the energy mismatch. The current RED-S model recognizes that low energy availability exists along a spectrum rather than as one universal cutoff that affects everyone identically.
RED-S Can Affect Athletes of Any Gender
RED-S evolved from earlier conversations about the Female Athlete Triad, which focused primarily on low energy availability, menstrual dysfunction, and impaired bone health. Those issues remain extremely important, but our understanding has expanded. We now know that inadequate energy availability can affect many systems throughout the body and can occur in athletes of any gender.
For athletes who menstruate, changes in the menstrual cycle can be an important warning sign. Losing a period because of training or inadequate nutrition should not automatically be considered a normal consequence of being an athlete.
For athletes who don't menstruate, RED-S may show up through other changes, including fatigue, decreased performance, bone injuries, impaired recovery, changes in hormones or libido, mood changes, or frequent illness.
You Don't Have to Be an Elite Athlete to Develop RED-S
The word "sport" can make RED-S sound like something that only happens to professional, collegiate, or Olympic athletes.
It isn't. RED-S can occur in anyone whose activity demands consistently exceed the energy available to support them.
That might include:
High school and collegiate athletes
Recreational runners
Dancers
Gymnasts
Cyclists
Swimmers
Endurance athletes
Weight-class athletes
Team sport athletes
Competitive lifters
People training for races or other athletic events
People exercising intensely without identifying themselves as "athletes"
You don't need a coach or a professional contract for your body to need adequate fuel.
RED-S and Eating Disorders
RED-S and eating disorders can overlap, but they aren't the same thing. An athlete can experience RED-S without having an eating disorder. At the same time, athletes with eating disorders or disordered eating may be at increased risk of developing low energy availability.
Sports environments can sometimes make it harder to recognize disordered behaviors because restriction, rigid eating, compulsive exercise, or pursuing a lower body weight may be praised as "discipline."
An athlete may hear messages like:
"You just need to be leaner."
"Don't undo your workout."
"You have to earn your food."
"Lighter is faster."
"Everyone on the team watches what they eat."
These messages can make harmful behaviors feel normal, particularly in sports where appearance, weight, endurance, or body composition receive a lot of attention. Supporting an athlete with RED-S means looking beyond nutrient calculations.
Can You Have RED-S in a Larger Body?
Yes. Body size alone cannot tell us whether someone is adequately fueled.
An athlete does not have to appear thin or lose a significant amount of weight to experience low energy availability.
Assuming that larger-bodied athletes are automatically eating enough not only delays recognition and treatment, but it also leads to recommendations for intentional weight loss when an athlete may already be inadequately fueled.
Weight-inclusive RED-S care focuses on whether the athlete is receiving enough nutrition to meet their individual needs rather than using appearance or body size as a shortcut for determining health.
How is RED-S Treated?
There isn't one universal RED-S meal plan. Treatment depends on the athlete's symptoms, medical status, training demands, eating patterns, sport, relationship with food, and whether an eating disorder or other medical condition is also present.
Nutrition treatment will often involve increasing energy availability.
That may include working on:
Eating consistently throughout the day
Increasing overall food intake
Fueling before training
Replenishing energy after training
Eating enough carbohydrates to support activity
Getting adequate protein throughout the day
Including sufficient dietary fat
Increasing snacks around practices or competitions
Developing portable fueling options
Managing GI discomfort while maintaining adequate nutrition
Challenging restrictive food rules
Supporting adequate hydration
Making fueling realistic within school, work, travel, and practice schedules
Treatment may also involve adjusting training while the body recovers.
Because RED-S can affect multiple systems of the body, care is often most effective when provided by a multidisciplinary team. Depending on the athlete's needs, that team may include a physician, sports medicine provider, registered dietitian, therapist, athletic trainer, physical therapist, coach, or other healthcare professionals. The IOC has also developed a clinical assessment framework called the REDs CAT2 to help qualified healthcare professionals evaluate possible RED-S and consider participation and treatment recommendations.
What Does a RED-S Dietitian Do?
A dietitian who understands RED-S can help determine whether an athlete's current fueling pattern is keeping up with what their body and sport require.
At CV Wellbeing, nutrition counseling may include exploring questions like:
Are you eating often enough to support your training?
What happens to your appetite on practice or competition days?
Are there long gaps between meals and snacks?
Do you have enough foods available before and after training?
Are food rules making it harder to meet your needs?
Are GI symptoms interfering with your ability to fuel?
Do you experience guilt or anxiety around eating or resting?
Does your training schedule leave enough time for eating and recovery?
Are sensory needs, executive functioning, or a busy schedule making consistent nutrition more difficult?
Are messages from coaches, teammates, social media, or sports culture affecting your relationship with food or your body?
The goal is to create a fueling approach that is adequate, flexible, sustainable, and realistic for the athlete in front of us.
Nutrition Support for RED-S at CV Wellbeing
CV Wellbeing is excited to have Jane Pfeufer, MS, RDN, LD and Josh Palomera, MS, RDN, LD, CSN on our dietitian team, bringing additional expertise in sports nutrition, RED-S, eating disorders, and helping athletes adequately fuel for both performance and long-term health.
Our approach to sports nutrition is weight-inclusive and grounded in the belief that athletes deserve support without fear-based food rules, pressure to shrink their bodies, or the assumption that performance should come at the expense of health.
Whether you're currently experiencing symptoms of RED-S, recovering from an eating disorder, struggling to fuel consistently, navigating collegiate athletics, dealing with repeated injuries, or simply wondering whether you're eating enough for your activity level, nutrition counseling can give you a place to sort through what's happening.
You don't have to wait until your performance falls apart or your symptoms become severe to ask for help. Your body deserves enough energy for your sport and enough energy for everything outside of it, too.
Looking for RED-S or Sports Nutrition Support?
Our dietitians can help athletes build practical fueling strategies, navigate low energy availability and RED-S, recover from disordered eating, and develop a relationship with food that supports both athletic participation and life outside of sport.