Avoid Under Fueling for Your Sport - RED-S

Relative Energy Deficiency in Sport: Food is Fuel

What is relative energy deficiency in sport?

Imagine trying to drive your car on an empty tank of gas. There’s no fuel for your car so it begins to lose function and it eventually breaks down. This is similar to what happens to the bodies of athletes when they do not eat enough food to support their level of physical activity. This is called relative energy deficiency in sport or RED-S. Relative energy deficiency in sport is a syndrome that occurs when an athlete does not consume enough food to replenish their energy stores. It is often accompanied with declining athletic performance and poor health.1

Just like how a car with no gas begins to break down, so does the body of an individual with RED-S. Some areas of the body that begin to suffer from this energy deficit include the reproductive, immune, endocrine, nervous and skeletal systems. Some symptoms of RED-S include irregular periods, low libido, decreased bone density, irregular heart rhythms, depression, anxiety, and a weakened immune system.1

Now imagine trying to play an entire soccer game or volleyball tournament with all those symptoms. Not only would an individual's athletic performance be in jeopardy, but so would their long term health. The consequences of RED-S can cause long term side effects if not taken seriously and addressed appropriately. Luckily, athletes have the ability to prevent and reverse RED-S through proper nutrition. 

Is it the same thing as the female athlete triad?

RED-S may seem similar to what has been referred to in the past as The Female Athlete Triad. The female athlete triad is a combination of an energy imbalance with or without the presence of an eating disorder, irregular menstruation, and osteopenia or osteoporosis in females. However, in 2014, the International Olympic Committee replaced the term female athlete triad with RED-S to be more inclusive of all genders.1 Although women are thought of to be more likely to struggle with disordered eating or underfueling, male athletes are just as susceptible to developing RED-S. According to a study published by Nutrients, approximately 26% of male athletes are at a medium to high risk of developing RED-S.2

Furthermore, male athletes often fall between the cracks when it comes to assessing underfueling, RED-S, or eating disorders because the general stereotype for these issues is female. However, it is important for coaches, parents, and practitioners to acknowledge these gender biases and counteract them so that their athletes and patients can receive the best care possible. One of the most critical parts of treating and preventing RED-S is improving nutrition and this is where registered dietitians can become an integral part of the care team.

Combatting RED-S through Nutrition 

Because RED-S is caused by an insufficient intake of calories, it can be prevented and treated by increasing an athlete’s intake of food. One way that an athlete can increase their intake is by adding pre-workout and post-workout snacks. Not only does this positively affect their health, but it also positively affects their performance. 

A pre-workout snack should contain carbohydrates and should be eaten approximately thirty minutes before the athletic event. Carbohydrates provide the body with glucose, which the body uses as energy or fuel during athletic performance. Some great pre-workout snacks include fruit such as an orange, applesauce, honey stinger waffles, cheese sticks, pretzels, and smoothies.

A post-workout snack should contain a combination of protein and carbohydrates. Protein is needed to repair muscles that have been used and exhausted during an athletic event. Carbohydrates are needed to replenish glucose stores. These glucose stores help stabilize energy levels and prevent fatigue. A post-workout snack is most effective when eaten approximately within thirty minutes of finishing exercise. Some examples of post workout snacks include chocolate milk, apple slices with a cheese stick, yogurt and granola, a protein shake, or a ham and cheese sandwich. 

Lastly, athletes should be consuming meals and other snacks consistently throughout the day. Meals should contain a balance of carbohydrates, proteins, and fats. Oftentimes athletes must eat more food than they think they need to properly fuel their energy needs. Additionally, it can be difficult for athletes to find time in their busy schedules to sit down and eat a meal. This is where the registered dietitian can assist with making sure the athlete is getting enough food, properly timing out meals and snacks, and they can give an overall evaluation of the athlete’s relationship with food. 

RED-S Conclusion

Just like how a car without gas can not properly function, neither can an athlete who is not eating enough food. RED-S is a syndrome caused by an energy deficiency in athletes and it negatively affects athletic performance and health. Some symptoms of RED-S include issues with the reproductive, immune, endocrine, cardiovascular, nervous and skeletal systems. The best way to treat and prevent RED-S is by making sure the athlete is consuming enough calories. This can be done by eating consistent meals and snacks throughout the day, and adding in pre and post-workout snacks as needed. 

The thought of consuming more food may seem scary or overwhelming to some individuals. Registered dietitians serve as food and nutrition experts that can guide athletes in the right direction when it comes to properly fueling their body and creating a healing relationship with food. Just like it takes a team to win games, it takes a team to build a healthy athlete.

References

Relative energy deficiency in sport (reds). Boston Children’s Hospital. 2025. Accessed February 8, 2025. https://www.childrenshospital.org/conditions/reds. 

Marzuki MIH, Mohamad MI, Chai WJ, et al. Prevalence of Relative Energy Deficiency in Sport (RED-S) among National Athletes in Malaysia. Nutrients. 2023;15(7):1697. Published 2023 Mar 30. doi:10.3390/nu15071697

If you are an athlete looking to learn more about fueling properly for your sport schedule a session with our sports dietitian McKayla Mazziotti MS, RD, LD by clicking the link below.