Why 1900 kcal is often too low for an active athlete

Most active athletes chronically undereat, hoping to lose fat faster. Usually the opposite happens: the weight stalls, energy drops, and training feels harder than it should. If you run, lift and train for Hyrox in the same week, 1900 kcal almost never matches what your body actually burns.

What "maintenance calories" really means for a hybrid athlete

Your maintenance — your TDEE, or total daily energy expenditure — is everything your body burns in a day: your resting metabolism, daily movement, and the energy cost of training. For a hybrid athlete who combines endurance work with strength training, that last part is big. A long run, a heavy lower-body session and a Hyrox-style conditioning workout in the same week each add hundreds of kilocalories on top of your baseline.

For someone who runs and lifts regularly, maintenance often sits between 2400 and 2800 kcal, not 1900. That 1900 figure comes from twenty-year-old diet logic written for a sedentary day, not from what a training body needs now. Age shifts the number a little — metabolism and recovery do change over the years — but training volume moves it far more than your birth year does.

You can estimate maintenance with the Mifflin-St Jeor formula plus an activity factor, then adjust from real-world results. That's exactly what the HybridFuelCo app does in one tap: it calculates your personal maintenance and macros from your weight, height, age and training load, free — so you start from your own numbers instead of a generic internet figure.

Why cutting too deep backfires

An extreme deficit costs you muscle, not just fat — and when you train hard, holding onto muscle is the whole game. Strength, power and the ability to repeat efforts in a Hyrox race all depend on the lean mass you're trying to protect. Cut too aggressively and you lose exactly the tissue that makes you fast.

It doesn't stop there. On a steep cut you recover worse between sessions, sleep lighter, your hormones shift, and hunger eventually wins. Within a few weeks most people quit, and the weight comes back. That's not a lack of willpower; it's biology reacting to too steep a drop in energy. The body defends itself against what it reads as starvation, and training only sharpens that signal.

The signs you're eating too little

Undereating rarely announces itself. It shows up as a cluster of smaller things: a scale that won't move despite a disciplined week, workouts that feel heavy from the first rep, a resting heart rate that creeps up, poor sleep, a short fuse, and cravings that hit hard in the evening. Women may notice cycle changes; everyone tends to notice strength stalling. If several of these line up while you're "being good" with food, the problem is usually too little fuel, not too little discipline.

Do it this way instead

• Find your maintenance first — calculate it or let the app do it, then treat it as a starting estimate you refine over two to three weeks.
• Pick a moderate deficit: roughly 300–500 kcal below maintenance, good for about 0.5–1% of bodyweight per week. Sustainable, and it protects muscle.
• Keep protein high — around 1.8–2.2 grams per kilo of bodyweight per day, spread across your meals. This is the single biggest lever for holding onto muscle in a cut.
• Don't fear carbs around training. Carbohydrate is fuel for hard sessions and a Hyrox effort, not the enemy. Put the bulk of your carbs before and after the work.
• Adjust on evidence, not emotion. If weight and performance are steady for two weeks, nudge intake; don't slash it on a bad day.

A realistic day at maintenance

To make it concrete, here's roughly what 2500 kcal with high protein can look like for a hybrid athlete on a training day: oats with Greek yoghurt, berries and honey in the morning; a lunch built around a lean protein, rice or potatoes and vegetables; a handful of fruit and nuts around training; and an evening plate of fish or lean meat with carbs and plenty of veg. Nothing exotic — just enough food, timed sensibly, to cover the work. The exact grams are what the app fills in for you.

Eat enough to fuel the work, cut moderately, and give it time. A slow, boring approach beats any crash week — and it's the only one that still leaves you strong on race day. For the timing side of this, read our guide on eating around training, and if you batch-cook, see meal prep for Hyrox.