Low energy availability in athletes

Also called: RED-S; relative energy deficiency in sport; the female athlete triad

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Not eating enough for the training being done, which suppresses hormones, bone density, immunity and recovery. The cruel part is that the instinctive response - training harder - makes it worse rather than better.

How common: Up to 45% of female athletes and a substantial minority of male athletes in lean sports

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What it is

Relative energy deficiency in sport is a state where energy intake is insufficient to support both training and normal physiological function. The body responds by downregulating the systems it can live without in the short term: reproductive hormones, bone formation, immune function, metabolic rate and growth.

It affects both sexes, though the female athlete triad - low energy availability, menstrual disturbance and low bone density - was recognised first and remains the clearest presentation. Absent or irregular periods in a training athlete is not a sign of fitness; it is a signal that the system is being run at a deficit.

What it feels like

Performance plateauing or declining despite training harder
Constant fatigue and slow recovery between sessions
Irregular or absent periods in women; reduced libido in both sexes
Frequent illness and repeated injuries, particularly bone stress injuries
Feeling cold, and low mood or irritability

What causes it

Most people have more than one of these at once, and they feed each other. Read the list looking for the two or three that sound like your week rather than for the one true answer — the ones that describe you are the ones worth acting on.

Intake insufficient for the training load: The core mechanism. It may be deliberate restriction, it may be an appetite that has not kept pace with a rising load, or it may simply be not knowing how much is required.
Increasing training without increasing intake: The most common inadvertent route. Volume rises through a season and eating does not, producing a gradually deepening deficit that nobody notices happening.
Deliberate restriction for body composition: Pressure to be lighter is intense in endurance, aesthetic and weight-category sports. It is frequently coached rather than self-imposed, which matters when addressing it.
Disordered eating and eating disorders: Present in a substantial proportion of cases, particularly in aesthetic and endurance sports. It needs specialist help rather than a nutrition plan.
Suppression of reproductive hormones: The body downregulates reproduction first when energy is short. In women this produces menstrual disturbance; in men, lowered testosterone. Both then affect bone.
Impaired bone formation: Low energy availability suppresses bone-building directly and, through lowered sex hormones, indirectly. Bone stress injuries are the most visible consequence and are often the presenting problem.
Reduced metabolic rate: The body lowers resting energy expenditure to defend against the deficit, which makes further weight loss harder and creates the impression that even less food is needed.
Impaired immunity and recovery: Repeated illness and slow recovery between sessions are early and easily dismissed signs, usually attributed to training hard rather than to under-fuelling.
Training harder in response: The instinctive reaction to declining performance is to train more, which deepens the deficit. It is the single most damaging feature of the condition.
Nobody asking: Menstrual disturbance in athletes is routinely normalised by athletes, coaches and clinicians. Asking the question directly is the most useful thing anyone in the environment can do.

Who tends to get it

Endurance athletes - distance running, cycling, triathlon
Aesthetic sports - gymnastics, dance, diving, figure skating
Weight-category sports - combat sports, lightweight rowing, jockeys
Anyone with menstrual disturbance while training
Athletes with repeated bone stress injuries or frequent illness

What makes it worse, and what settles it

Makes it worse

Training harder in response to declining performance
Further restricting intake to change body composition
Normalising absent periods as a sign of being fit
Continuing to train through repeated bone stress injuries
Coaching cultures that emphasise weight over performance and health

Settles it

Increasing energy intake to match the training load - this is the treatment
Reducing training volume temporarily while intake is restored
Working with a sports dietitian, and where disordered eating is present, with a specialist team
Getting bone density and hormonal status assessed
Resistance training, which supports bone once energy availability is restored

What actually helps

The short version: Insufficient energy intake for training load, suppressing hormones, bone density, immunity and recovery. More training makes it worse, not better

Strength work: MORE EXERCISE IS THE WRONG PRESCRIPTION. Resistance training only once energy intake is corrected

Stretching: Not the issue

Massage: Not the issue

Also worth doing: Increase energy intake; reduce training volume; medical and dietetic support

What the evidence says: A negative entry by design. A fitness app that only encourages more training is actively dangerous to this group. Missed periods plus a stress fracture should trigger a caution, not a new program.

The names above are the Targets qFIT tracks — the Muscle Guide explains what each one does, and Quick Add switches on the Exercises you already have.

No ready-made routine for this one yet

249 of the 267 problems here have a routine already built, and this is not one of them — usually because the work that helps is covered by a general routine rather than needing its own. What actually helps above names the muscles and the work involved, which is enough to put it together yourself.

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Get it checked if…

Missed or lost periods, repeated stress fractures, persistent fatigue and frequent illness in someone training hard is RED-S until proven otherwise - refer

And whatever the body part: chest pain or unusual breathlessness on exertion; a fever alongside the pain; unexplained weight loss; pain that is constant and unrelated to how you move; new numbness, weakness or loss of bladder or bowel control; or one calf that is swollen, warm and painful. Any of those, stop and get assessed.

How it usually goes

Menstrual function typically returns within months of restoring energy availability, and performance follows. Bone density recovers more slowly and, where the deficit was long-standing during adolescence, may never fully recover - which is why early recognition matters so much. The most important shift is understanding that the answer is more food and less training, which is the opposite of every instinct an athlete has. Where disordered eating is involved, this needs a specialist team rather than a nutrition plan.

Prevalence basis: Sports medicine screening studies

This is general information, not a diagnosis, and it cannot examine you. If it matches you, use it to ask better questions of a clinician rather than to replace one.

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