Low energy availability in athletes: why fuelling “enough” isn’t always enough
August 20, 2026
If you’re training hard and still hitting a wall, plateauing for no clear reason, getting injured more than you used to, or just not recovering the way you did last season, there’s a concept worth knowing about that doesn’t get nearly enough airtime in performance conversations. It’s called low energy availability, or LEA, and it’s quietly behind a lot of the frustrating patterns athletes experience.
What low energy availability actually means
Your body only has so much energy to go around each day. When you subtract what you use in training from what you take in through food, what’s left over is what your body has available to run everything else: hormones, immune function, bone repair, mood, cognition, recovery.
That remainder is your energy availability.
When it drops too low, not because you’re lazy or undisciplined but because the maths simply doesn’t add up, your body starts making decisions you didn’t authorise. It downregulates systems that aren’t immediately essential to survival. Reproductive hormones dip. Bone turnover shifts. Immune function weakens. Your body prioritises staying alive over performing well, because as far as it’s concerned, energy is scarce and something has to give.
This is physiology, not a willpower problem. It’s the same underlying process described in the research on Relative Energy Deficiency in Sport, or RED-S, a term used to describe the wide-ranging effects of underfuelling relative to training demands [1].
What LEA actually looks like
LEA doesn’t always look like restriction, and it doesn’t require a dramatic story. It can develop gradually in athletes who are eating “plenty” by most people’s standards, simply because training load has crept up without fuel keeping pace. It can also happen in athletes with a genuine history of disordered eating, and in athletes who have never restricted intentionally in their life. Both are common, and both deserve the same careful attention.
Some of the patterns we see most often in clinic:
- Training feels heavier than it should for the effort you’re putting in
- Recovery is slower and soreness lingers, you never quite feel fresh
- You’re relying on caffeine just to feel functional
- Performance at the pointy end disappears and the top gear isn’t there
- You’re thinking about food a lot, or feeling preoccupied with eating
- Mood feels flat or irritable and focus is harder to hold
- Injuries and niggles that won’t resolve, or keep recurring
- Periods becoming irregular or disappearing
- Libido dropping, or noticeably lower testosterone in male athletes
- Getting sick more often than teammates on the same program
None of these are dramatic on their own. Which is exactly why they get normalised. “I’m just tired from training.” “This is what hard training feels like.” “I need to push through.” That internal narrative makes sense, especially in sporting culture where discomfort is often worn as a badge of commitment. But if the underlying cause is low energy availability, pushing through doesn’t fix it. It tends to deepen it.
If any of this sounds familiar and you’re not sure whether it’s normal training fatigue or something more, that’s exactly the kind of question worth bringing to an appointment rather than trying to work out alone.
Why “just eat more” is more complicated than it sounds
For some athletes, adjusting intake is relatively straightforward once they understand what’s happening and why it matters. For others, it genuinely isn’t, and that deserves acknowledgment rather than a quick fix.
Appetite cues can become dysregulated with LEA. Some athletes don’t feel hungry, even when significantly underfuelling. Others feel caught between knowing they need to eat more and finding it hard to act on that in practice, whether because of time pressure, gut symptoms during training, body image concerns, or a more complicated relationship with food and control. The link between food, body, and performance can become tangled in ways that aren’t resolved by information alone.
This is one of the reasons we approach this work from both a performance lens and a clinical one. Understanding why fuelling feels hard is just as important as knowing what to eat, particularly for athletes who are neurodivergent, who have a current or past eating disorder, or who are navigating this alongside conditions like POTS where appetite and energy regulation are already affected.
The number that matters, and why it’s a guide, not a target
Research on energy availability gives us a useful reference point. Optimal energy availability for most athletes sits at or above 45 kilocalories per kilogram of fat-free mass per day. Below 30 kcal/kg of fat-free mass per day is where significant physiological consequences reliably begin to appear, including disruption to reproductive hormones [2][3]. Many athletes are operating closer to this lower range than they realise, without any intention of restricting.
It’s worth being upfront here: this isn’t a number to calculate at home and use to judge yourself against. Energy availability is a clinical measure, it requires an accurate picture of training energy expenditure and body composition to mean anything useful, and self-calculating it can easily tip into the kind of number-focused thinking that causes more harm than it prevents, especially for anyone with a history of disordered eating. You don’t need to do the maths precisely to start paying attention to what your body is telling you. Knowing the concept exists is often enough to change how you interpret the signs above, and from there, a proper assessment is something to do with support rather than alone.
If you’re training seriously and some of this is resonating, it’s worth reading more broadly about fuelling for your specific sport and event demands. Our post on nutrition for multiple day events and tournaments covers some of the practical side of matching intake to load during competition blocks, which is often where the gap between training and fuelling widens the most.
Where this leaves you
If you recognise yourself in this, the goal isn’t to panic or to start eating differently overnight based on a blog post. It’s to take the pattern seriously instead of normalising it, and to get an assessment from someone who can look at the full picture, your training history, your relationship with food, your symptoms, and your goals, rather than a single number.
Low energy availability is common, it’s treatable, and it’s not a reflection of discipline or character. The athletes we see with LEA are, almost without exception, working hard and doing their best with the information they had at the time.
Getting support
If low energy availability sounds like it might be part of what you’re experiencing, you don’t have to work it out on your own. We work with athletes across sports and levels, both in person in East Brisbane and via telehealth wherever you’re based, to understand what’s actually going on and build a fuelling approach that supports both performance and health. If that’s something you’d find useful, you’re welcome to book a discovery call and we can talk through where to start.
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References
[1] Mountjoy M, Sundgot-Borgen J, Burke L, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. Br J Sports Med. 2018;52(11):687-697.
[2] Loucks AB, Thuma JR. Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. J Clin Endocrinol Metab. 2003;88(1):297-311.
[3] Loucks AB. Low energy availability in the marathon and other endurance sports. Sports Med. 2007;37(4-5):348-352.
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