Why Am I Not Recovering From Workouts? The Under-Fuelling Checklist
- Shrey Aggarwal
- Jul 17
- 6 min read
A long-distance runner came to me last year and asked, "Why am I not recovering from workouts?". She was convinced she had a thyroid problem. She was training well, eating what she called clean, and getting slower. Her bloodwork was normal. What she actually had was months of eating less than her training demanded, and her body had quietly started switching things off to cope.
She isn't unusual. Under-fuelling is one of the most common problems I see in committed amateur athletes, and it's almost always missed, because the person doing it looks disciplined, not unwell. They're training hard and eating carefully. The gap between the two is the problem.
Quick Overview
What under-fuelling actually is
Your body has a fixed amount of energy to work with each day. Training takes a share of it. Whatever's left has to run everything else: your heart, your hormones, your immune system, tissue repair, brain function, the lot. When you don't eat enough to cover both the training and the living, something has to give, and it isn't the training you already did. It's the maintenance work you can't see.
Sports scientists call this low energy availability, and it sits at the centre of a condition the International Olympic Committee calls Relative Energy Deficiency in Sport, or REDs (Mountjoy et al., Br J Sports Med, 2023). The idea is straightforward even if the name isn't: when energy runs short, the body downregulates functions to survive, and health and performance both suffer for it.
Long-standing shortfalls have been linked to menstrual and hormonal disruption, gut and cardiovascular problems, and weakened bones, all of which drag on performance (Logue et al., Nutrients, 2020).
It's more common than most amateurs assume. The IOC's 2023 review put the estimated prevalence among elite athletes across a wide band, anywhere from 15 to 80 per cent depending on the sport and how it's measured (Mountjoy et al., Br J Sports Med, 2023). Endurance athletes, weight-category athletes, and anyone chasing a leaner physique are most exposed, but it turns up in team-sport and recreational athletes too.
The checklist for "why am I not recovering from workouts?"
No single symptom confirms under-fuelling, and every symptom below has other possible causes, which is exactly why it gets missed (Jeukendrup et al., Sports Medicine, 2024). What matters is the pattern. If several of these are true at once, and they've crept in as your training load has gone up, under-fuelling is worth taking seriously:
You're tired in a way that sleep doesn't fix, and the tiredness is worse than your training alone should explain.
Your performance has stalled or gone backwards despite consistent training, and you're recovering slower between sessions.
You're picking up frequent minor illnesses or niggling injuries that don't settle.
You feel cold often, especially in your hands and feet, more than the people around you.
Your sleep has got worse, or you're waking unrefreshed.
Your mood, motivation, or drive to train has flattened.
For women, your menstrual cycle has become irregular, lighter, or stopped. This is one of the clearest warning signs the body is conserving energy, and it should never be dismissed as a normal part of hard training.
For men, a drop in sex drive can signal the same underlying energy shortfall.
Your digestion has become unreliable, with bloating or discomfort that wasn't there before.
None of these is proof on its own. Together, they're a signal that your intake and your output have drifted apart.
Why it hides in plain sight
Under-fuelling rarely looks like a problem from the outside, and often not from the inside either. The athlete is usually doing everything that gets praised: training consistently, eating whole foods, keeping lean, and showing discipline. Nothing about that reads as a warning.
Sometimes it's deliberate, driven by a belief that lighter always means faster. Often it's accidental. Appetite doesn't reliably rise to match a jump in training, so an athlete adds two hard sessions a week without adding any food and never notices the shortfall. Busy days make it worse when training goes up but eating stays squeezed around work.
The tricky part is that the early payoff can look like success. Losing a little weight while training hard often brings a short-term bump in performance, which reinforces the behaviour right before the decline sets in. By the time the fatigue and the stalled results arrive, the cause is months behind and hard to connect.
Why supplements won't fix it
This is where a lot of money gets wasted. When an athlete feels flat and stops recovering, the instinct is to reach for something: an iron supplement, a magnesium tablet, a recovery powder, an adaptogen. None of it addresses the actual problem, because the problem is a shortage of energy, and no pill contains energy in the sense the body needs here.
Under-fuelling is resolved by eating more, structured sensibly around training, and nothing else resolves it (Mountjoy et al., Br J Sports Med, 2023). A supplement can correct a specific measured deficiency once you've found one, but it can't refill the tank.
An iron supplement won't fix fatigue that's caused by not eating enough, and for a vegetarian athlete who does turn out to be iron-deficient, the iron works far better paired with a source of vitamin C than taken alone. The supplement is a tool for a narrow job, not a substitute for food.
How to turn it around
The fix is more food, but the way you add it matters more than the amount you obsess over. Adding energy back gradually and consistently works better than a dramatic overhaul, and it's easier to sustain.
Start by fuelling around your training rather than eating the same thing regardless of what the day holds. On heavy days, eat more, and put carbohydrates before and after the hard sessions so the work is actually supported. Carbohydrate is the fuel most often cut and most needed, and it's usually the first thing to restore. Stop treating every session as something to be done depleted; chronic fasted training is a common route to this problem.
Spread food across the day instead of banking it all into one evening meal, so you're not running on empty through your training and recovery windows. And give it time. The symptoms of under-fuelling took months to appear, and they take weeks of consistent eating to lift, not days. If your cycle has stopped, its return is one of the better signs that things are genuinely back on track.
If any of this feels harder than it should, if eating more brings up real anxiety, or if the under-fuelling is tied to a difficult relationship with food, that's worth taking to a professional rather than pushing through alone. Under-fuelling and disordered eating overlap often enough that good practitioners always keep the connection in mind (Mountjoy et al., Br J Sports Med, 2023).
Fueletics Perspective
The athletes who plateau are rarely the ones training too little. More often they're the ones eating too little for the training they're already doing, and no amount of extra effort digs them out, because effort isn't the missing ingredient. Energy is.
If you're tired in a way rest won't fix, recovering slowly, and stalled despite doing everything right, the first question isn't what to add to your training or your supplement shelf. It's whether you're eating enough to support the athlete you're asking your body to be. That's an unglamorous answer, and it's the one that works.
If you want to know whether your intake actually matches your training, rather than guessing, that's what the Fueletics sports nutrition assessment is built to show you.
This is a topic that shades into disordered eating for some people. If that's you, or someone you're reading this for, a qualified sports dietitian or your doctor is the right place to start, and reaching out is a strength, not a failure.
Research References
Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 2023;57(17):1073-1097. https://doi.org/10.1136/bjsports-2023-106994
Jeukendrup AE, Areta JL, Van Genechten L, et al. Does Relative Energy Deficiency in Sport (REDs) Syndrome Exist? Sports Medicine, 2024;54(11):2793-2816. https://doi.org/10.1007/s40279-024-02108-y
Logue DM, Madigan SM, Melin A, Delahunt E, Heinen M, Mc Donnell S-J, Corish CA. Low Energy Availability in Athletes 2020: An Updated Narrative Review. Nutrients, 2020;12(3):835. https://doi.org/10.3390/nu12030835
