Under-eating in a HYROX block looks exactly like overtraining. Flat sessions, poor sleep, no progress, low mood. So people do the logical thing and train less, when the actual problem was on the plate.
Hybrid training is unusually good at causing this, because it stacks running volume and strength work in the same week, and appetite does not reliably rise to meet the two together.
Why trust this
The format is the reason this is a hybrid-specific problem. A HYROX asks for 8km of running and eight loaded stations in the same event, so a block asks for both in the same week. Runners under-eat and lifters usually do not; someone doing both often eats like a lifter on gym days and like a runner on run days, and ends the week short.
There are no statistics on this page. There is no reliable published figure for how common under-fuelling is among HYROX athletes, and inventing one would undermine the point.
The signs, and why each one is easy to misread
| Sign | What people assume | What it may actually be | |---|---|---| | Sessions harder at the same pace or load | "I need more training" | Not enough fuel to run the training you already have | | Sleep getting worse in the hardest weeks | "Stress, or too much caffeine" | Under-eating, which reliably disturbs sleep | | Constant low-grade colds | "Bad luck, busy season" | Under-recovery, of which food is half | | Mood flat, irritable, short-fused | "Work" | Same | | Progress stalled for a month | "I have plateaued, add volume" | Adding volume to this makes it worse | | Always cold, particularly hands and feet | Rarely connected to training at all | A classic and widely under-recognised sign | | Periods becoming irregular or stopping | "Normal for athletes" | Not normal, and worth medical attention |
That last row deserves emphasis. Menstrual changes in a training block are a signal that energy availability is too low, not a badge of being fit. It warrants a doctor rather than a training adjustment.
Why hybrid athletes specifically
Running suppresses appetite; lifting raises it. Do both in a week and the signals conflict.
The training does not feel like it burns much. A 40-minute easy run and two gym sessions do not feel like a big week. Across seven days, with 8km-plus of running and loaded work, the total is larger than it feels.
Fat loss and performance get pursued simultaneously. Very common in a first HYROX block, because people arrive wanting both. It is the single most reliable way to get neither.
Taper weeks make it worse, not better. Volume drops, appetite drops with it, and then race week arrives with two days of loading that lands on an already-depleted athlete.
The practical part: what to do about it
- Track for four days, honestly, including the weekend. Not forever. Four days tells you whether you are anywhere near the mark.
- Protein first: 1.6 to 2.0 g per kg per day. Most people under-eating are under here, and it is the easiest thing to correct.
- Add carbohydrate around the sessions, not across the day. Before and after training is where it does the most work.
- Eat on the day the training is hardest, not the day after. Very common error: light eating on the big day, catch-up eating the next.
- Do not run a deficit through the middle of a build. If body composition matters, do it before the block starts or after the race.
- Treat a rest day as a normal eating day. Recovery is when the building happens. Cutting food on rest days removes the materials.
- If three or more signs above are present, add food before you subtract training. It is the cheaper experiment and the faster one.
What this is not
This page is about energy availability in a training block. It is not about eating disorders, which are a serious clinical matter and outside what a training site can responsibly address.
If food, weight or training has stopped feeling like a choice, that is a conversation with a doctor, and it deserves one regardless of what any programme says. Nothing here should stand in the way of it.
Honest limitations
Every sign listed above has other explanations. Poor sleep might be a new baby; feeling flat might be work. Under-eating is a common cause, not the only one, and this page cannot diagnose you.
The macro ranges given are general guidance rather than a personalised plan, and the honest test is not a number on a tracker: it is whether your training, sleep and mood improve when you eat more.
Next step
Most under-fuelling in a HYROX block comes from a plan that asks for more than the athlete realised. The HYROX training plans show you the actual weekly load in advance, so you can eat for it rather than discover it.
The fitness assessment quiz sets a realistic starting point, which is the other half of not overreaching.
Related
- HYROX macros: the protein, carbohydrate and fat targets this page refers to.
- HYROX 12-week nutrition timeline.
- HYROX recovery: sleep, mobility and the habits that compound.
- Fat loss: what actually works, if body composition is the goal.
[ FAQ ]
Frequently asked
How do you know if you are under-eating in training?
The usual pattern is several signs at once: sessions feeling harder at the same paces, sleep getting worse rather than better in hard weeks, persistent low mood or irritability, frequent minor illness, and progress stalling despite consistent training. Any one alone means little. Three together is worth acting on.
Can you lose weight while training for a HYROX?
You can, but running a meaningful deficit through a hard twelve-week build usually costs you more in training quality than it gains you in body composition. If both matter, the deficit belongs before the block or after the race, not through the middle of it.
Why am I not improving despite training hard?
Under-recovery is the common cause, and under-eating is one of the two big drivers alongside poor sleep. Training is the stimulus; food and sleep are what turn it into adaptation. Adding more sessions to a body that cannot absorb the current ones makes it worse.
Written by
The Suth Performance teamCoaches and editors
The Suth Performance programming team, led by HYROX Elite 15 athlete Ben Sutherland. They write the training, technique and race-day guides on this site, and Ben reviews every one before it is published.
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