Under-fuelling in athletes (REDs): injuries and warning signs
Some athletes train hard, eat 'clean', and still keep getting injured, sick or flat. Often the missing piece is simply not eating enough to match the training. The International Olympic Committee calls the resulting syndrome Relative Energy Deficiency in Sport, or REDs.
This is general information, not individual dietary advice. Steven is an osteopath, not a dietitian. For a plan tailored to you, particularly if you have a medical condition, see your GP or an Accredited Practising Dietitian or sports dietitian.
What is REDs?
REDs is a syndrome of impaired health and performance caused by low energy availability: when the energy you eat, minus the energy used in training, leaves too little for the body's normal functions over a prolonged period. The IOC's 2023 consensus statement describes effects on many body systems, including hormones, bone, metabolism, immunity, the gut, mood and performance (Mountjoy et al., British Journal of Sports Medicine, 2023).
Who gets REDs?
It can affect any athlete, female or male, at any level. Risk is higher in endurance sports such as running, cycling and triathlon, weight-category sports such as boxing, judo and BJJ competition, and sports that emphasise leanness, such as dance and gymnastics. It also happens unintentionally, when training increases and eating doesn't.
What are the warning signs?
Common signs include missed, irregular or lighter periods in women, low libido in men, repeated injuries (especially bone stress injuries), frequent illness, persistent fatigue, poor sleep, low mood or irritability, feeling cold, gut problems, and a plateau or drop in performance despite hard training. Not everyone loses weight; body weight can be stable.
How does under-fuelling affect bones?
Low energy availability suppresses the hormones that maintain bone, including oestrogen and testosterone. Over time bone density can fall and the risk of bone stress injuries rises. This matters most in teenagers and young adults, when peak bone mass is still being built.
See our post on vitamin D, calcium and stress fractures.
Is losing your period normal for athletes?
No. It's common, but it isn't a normal or harmless sign of being fit. A missed period for three months or more, or periods that haven't started by age 15, should be assessed by a GP. Being on the contraceptive pill can mask this sign.
Does REDs affect men?
Yes. In men it tends to show up as low libido, fatigue, reduced morning erections, recurrent injuries, low testosterone and poor recovery.
How is REDs different from an eating disorder?
REDs is about the energy mismatch, whatever the cause. It can occur without any disordered eating, for example in a busy athlete who simply doesn't eat enough. It can also occur alongside disordered eating or an eating disorder, which needs specialist support.
How is REDs diagnosed and treated?
Diagnosis is made by a doctor, ideally a sports physician, using history, examination, blood tests and sometimes a bone density scan. Treatment centres on increasing energy intake, sometimes with a temporary reduction in training, guided by a sports dietitian, with psychological support where needed. Bone stress injuries are managed alongside.
How can I make sure I'm eating enough for my training?
Eat regular meals and snacks, including carbohydrate around training. Increase food on heavier training days rather than keeping it constant. Avoid long gaps without eating, and avoid training fasted for long or hard sessions. If you're trying to lose weight for sport, do it slowly, out of season, and with a dietitian's guidance.
What about weight cutting for combat sports?
Rapid weight cuts and long periods of restriction are a known risk in BJJ, judo, boxing and Muay Thai. Competing closer to your natural weight, and planning any weight change well ahead with professional help, protects both health and performance.
What should parents and coaches look for?
A young athlete who is repeatedly injured, always tired, losing weight or not growing as expected, has stopped having periods, or has become rigid or anxious about food deserves a conversation and a GP visit. Avoid comments about weight and body shape.
How can an osteopath help?
We often see the injuries first: a second or third stress fracture, or tendons that won't settle. Part of our job is to ask about training, recovery and periods, recognise the pattern, and refer you to a GP, sports physician or sports dietitian, while managing the injury and your return to training.
When should I see a doctor?
See your GP for missed periods, repeated bone stress injuries, ongoing fatigue or dizziness, fainting, a very low heart rate with symptoms, or if eating and body image are causing distress. The Butterfly Foundation helpline (1800 33 4673) offers support for eating and body image concerns.
See our training hub and our post on training load errors. Book an assessment at our Berwick clinic. A 60-minute initial consultation is $149, with no referral needed and HICAPS on-site.
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Book an initial consultation at RISE Sports & Spinal in Berwick. Clear diagnosis, hands-on treatment, and a plan that actually gets you better.
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