What low energy availability means
Energy availability is the energy left for the body's basic functions after exercise has taken its share. When that residue is too small - because intake is low, training is high, or both, the body starts prioritising.
In a growing adolescent, growth itself is one of the competing demands, which is why the same shortfall matters more at 14 than at 24.
Early, easy-to-miss signs
- Tiredness that does not improve with a lighter week.
- Low mood, irritability or anxiety around training.
- Recurring small injuries and niggles that move around.
- Feeling cold much of the time.
- Poor sleep despite being exhausted.
- Reduced enthusiasm for sport she previously loved.
Harder signals
- Periods becoming irregular, lighter, or stopping.
- Delayed onset of periods in a heavily training athlete.
- A bone stress injury, particularly a second one.
- Measurable performance decline over a season.
- Frequent illness or infections that linger.
Why it happens in ordinary families
This is not primarily a story about eating disorders, though they do occur and need specialist help. Far more often it is a busy schedule: training four or five times a week, long gaps between meals, a growth spurt raising requirements, and nobody adjusting the food.
Sport culture can contribute too - comments about physique, weight-focused coaching, and comparison in fitted kit all raise the risk of restriction in adolescent girls.
What to do first
- Add food rather than removing training: an extra snack before and after every session.
- Make carbohydrate at every meal the default for a training athlete.
- Review the weekly training load and remove any low-value duplicated volume.
- Protect sleep, 8–10 hours.
- Re-check in four to six weeks: energy, mood, performance and cycle.
When to involve a professional
See a GP if periods are absent or have stopped for three months, if there has been a bone stress injury, if weight is falling, or if there is any sign of disordered eating. Ask specifically about bone health and iron status.
Addressed early, low energy availability usually resolves with straightforward changes to eating and scheduling. Left for a year, it can cost bone density that is difficult to recover.