Losing weight shouldn't mean
running on empty.

Energy availability is what's left over for your body to run on — hormones, bones, immune function, reproductive health, recovery — after you subtract what training costs you. It's a different question to "am I in a deficit," and it's the one that actually determines whether weight loss is happening safely.

The more active you are, the bigger the gap can get between "eating less" and "leaving your body with enough to actually function." This catches capable, disciplined people more often than anyone else — the ones most likely to push through warning signs rather than listen to them.

The signs worth taking seriously

No single sign confirms anything on its own. It's the pattern and the trend that matter — especially several of these showing up together, or getting worse over weeks rather than settling down.

Physical

• Losing or missing periods, or unusually light cycles
• Getting cold easily, or resting heart rate creeping down further than usual
• Frequent illness or infections that hang around
• Stress fractures, or niggles that aren't healing as expected
• Digestive changes — constipation, bloating, or reflux that's new

Performance

• Recovery between sessions taking noticeably longer
• Strength or pace dropping despite training consistently
• Feeling flat or heavy in sessions that used to feel fine
• Increased injury frequency

Psychological

• Preoccupation with food or training that's crowding out other things
• Irritability, low mood, or anxiety that feels out of character
• Sleep that's become lighter or more disrupted
• Guilt around rest days or missed sessions

A simple self check-in

This isn't a diagnosis — it's a prompt to bring things up rather than push through them. Be honest rather than optimistic when you go through it.

• I've noticed a change in my menstrual cycle, or (for men) a drop in morning erections or libido, since starting to lose weight.
• My training performance has gone backwards over the last few weeks, not just plateaued.
• I've picked up more colds, niggles, or injuries than usual in this block.
• I think about food, my body, or "earning" meals more than I used to.
• I feel guilty or anxious about eating enough on rest days.
• I'm colder than usual, more tired than usual, or my sleep has gotten worse.

Why this matters more than people think

• It affects both sexes. This isn't just a women's issue — men experience the same underlying problem, often with less recognisable signs, which means it gets missed more often.
• Performance and body composition goals work against each other here. Chronic underfuelling tends to increase fat storage efficiency and reduce muscle retention over time — the opposite of what most people are chasing.
• Bone health impacts can take years to show up, and are not always fully reversible. This is not a "catch up later" problem.
• The fix usually isn't eating less harder. It's re-establishing enough energy availability first, then approaching any further fat loss goals more gradually and sustainably.