Relative energy deficiency in sport (REDS) is the term used for a collection of symptoms caused by an energy deficit. When individuals fail to get enough nutrition for the exercise they do, the body starts to shut down “non-essential” body systems to conserve energy.
This is an approach the human body has developed over thousands of years and would have previously allowed humans to survive through times of limited food availability.
Relative Energy Deficiency in Sport (RED-S) happens when your body isn’t getting enough energy to meet the demands of training and daily life.
RED-S can result from:
Often, it’s a mix of both. You might start eating less to improve performance, but then find it hard to return to normal eating—even when you want to.
Exercise can also lower hunger cues, making it harder to eat when your body needs fuel most.
Symptoms of REDS are incredibly varied as the body can shut down several different systems depending on the severity of the energy deficit.
Common symptoms include:
Here's a complete list of body systems affected by REDs.
We know that around 48% of athletes are likely to struggle with symptoms of REDS, although some of the research suggests this could be much higher. We know now these symptoms present in male athletes too.
If you are worried about any symptoms you are experiencing, visit the Project REDs website to find out more and access the right support and resources for you.
Watch this video to learn about how REDs impacted international 1500m runner, Bobby Clay.
If you haven’t already, consider talking to a GP. You can use our RED-S GP letter to help start that conversation.
If you're not ready for medical help yet:
RED-S symptoms come from under-fuelling. So, to feel better, it’s important to look at your eating patterns and energy intake.
Try increasing your energy intake over the next 6 months. This can help restore your menstrual cycle (if relevant) and reduce other symptoms.
To recover fully—and prevent RED-S from returning—try to understand why you’re under-fuelling.
Talking to someone (like a coach, doctor, friend, or nutritionist) can help. It might feel tough, but it gives you space to work things through and get the support you need.
Early intervention is essential to prevent long-term health effects of REDS such as reduced bone density, severe injuries, or poor mental health.
To prevent symptoms from occurring or worsening, athletes are encouraged to focus on their overall energy intake to ensure they are getting enough. RED-S isn’t just about eating more—it’s about eating smart. More specifically, we now know that athletes must ensure they are getting enough carbohydrates before, during and after any exercise they take part in to compensate for the amount needed. Three key takeaways are:
Include carbohydrates with all three meals, especially the meal before you exercise. Foods like pasta, rice, potato, bread, noodles, cereals, couscous, oats.
Add a carbohydrate snack in 1-2 hours before any exercise. Good options would be a banana, slice of toast, crackers, cereal bar, pretzels, flapjack.
Carbohydrate snacks or drinks between matches or during long periods of exercise will keep your energy stores topped up. Things like fruit juice, jelly sweets, banana, malt loaf, cereal bar.
If you have more than an hour before your next meal, bring some snacks to help you recover. Chocolate milk, babybel and crackers, or a handful of mixed fruit & nuts will give you an energy and protein boost post exercise.
The protein, carbohydrates and vegetables within your first meal after exercise will help you replace energy, repair your muscles and prepare your body for the next day.
Milk before bed can support sleep and help you recover from any exercise you have done that day. A hot chocolate can be a great way to finish the day!
Trying to change your weight or body shape? That might have led to under-fuelling.
If increasing your food intake feels scary or uncomfortable, talk it through with someone you trust.
There’s a lot of misinformation out there, especially online. Visit our webpage to find out more on body image.
