Most riders know they should eat during races. They take a few gels, grab a bottle at the feed zone, and hope for the best. But hoping and planning are different things, and the difference usually shows up somewhere around hour three when the legs go hollow and the pace collapses. If you want to race well, you need to approach race fueling systematically — not as an afterthought, but as something you build and practise like any other part of your training.
What your body is actually doing when you race
Muscle glycogen is the limiting resource in most endurance races. Your body stores roughly 400–600 grams of carbohydrate across working muscles, plus another 90–120 grams in the liver — enough, at race intensity, to last somewhere between 90 minutes and two and a half hours before depletion starts to bite. Once glycogen drops below a threshold, your body is forced to slow down and lean more heavily on fat, which oxidises too slowly to maintain the power output you need at race pace. This is the physiological reality behind the bonk, and it is entirely preventable with a proper plan.
The other piece of the puzzle is that your gut has its own absorption ceiling. Glucose is transported across the intestinal wall via SGLT1 transporters, which max out at roughly 60 grams per hour. Add fructose — which uses a different transporter, GLUT5 — and you raise the ceiling to around 90 grams per hour in most trained riders. This glucose-to-fructose combination, typically in a 2:1 ratio, is why modern race products almost always blend the two sugars rather than relying on glucose alone. For context, the scientific literature supports 60–90 g/hr as the well-established target for endurance events longer than two hours, with higher intakes of 100–120 g/hr possible only after deliberate gut training.
Understanding the fundamentals of cycling fueling and hydration makes this easier to apply. Carbohydrate is your fuel, water and sodium maintain plasma volume and performance under heat, and the two interact — concentrated carbohydrate solutions slow gastric emptying, which is why drinking plain water alongside gels or bars can help absorption. None of this needs to be complicated, but it does need to be thought through before the race start.
Building the numbers for your specific race
A useful way to structure your fueling plan is to work backwards from race duration and intensity. For a race under 90 minutes at high intensity, glycogen will be stressed but you can probably get away with 30–40 g/hr, mostly as a liquid. For anything between 90 minutes and three hours, you want to be closer to 60–80 g/hr with a mix of liquids and solids. For races lasting more than three hours — gran fondos, sportives, long road races — target 80–90 g/hr and practise this number in training before you commit to it in competition.
The translation into products is where most riders make it overly complicated. One 40-gram energy gel every 30 minutes gives you 80 g/hr. A 500ml bottle of standard isotonic drink plus a bar in the first half gives you roughly 60–75 g/hr depending on the products. Real food — rice cakes, banana, dates — can work just as well for lower-intensity events and tends to sit better in the stomach than a stack of gels. What matters is not the form of the carbohydrate but that you are hitting the target consistently, not sporadically.
One number that is often overlooked is the pre-race meal. A meal two to three hours before the start, built around easy-to-digest carbohydrates (rice, oats, white bread, banana), topped off with a small carbohydrate snack 15–20 minutes before the gun, gives you full glycogen stores and a stable blood glucose going into the effort. This meal is part of the plan — it is not a substitute for in-race fueling.
The execution: timing, form, and what goes wrong
The single biggest fueling error is starting too late. Riders feel fine for the first 45 minutes, assume they can wait, and then play catch-up in the second half of the race. The gut can only absorb so much at once, and you cannot compensate for two hours of under-eating with a handful of gels in the final 30 kilometres. Start eating within the first 20–30 minutes, before hunger arrives, and maintain a consistent rhythm throughout. Eating every 20–30 minutes in small amounts is more effective than large, infrequent doses.
Let's be honest: racing makes eating harder. Your heart rate is elevated, your breathing is elevated, and the last thing your body is signalling is hunger. This is why practising your fueling plan in training is non-negotiable — not just to train your gut to handle the volumes, but to build the habit of reaching for food even when you do not feel like it. If you have done a six-hour ride in training eating 80 g/hr without GI issues, you know it works. Race day is not the moment to discover that a particular product sits badly in your stomach or that you cannot eat at threshold intensity.
Solid foods are easier to tolerate at lower intensities and become progressively harder above threshold. In a fast criterium or a hard road race with a constant high pace, gels and liquid carbohydrate are more practical than bars or real food. In a long sportive with varying terrain, mixing formats gives you more flexibility and generally sits better over four-plus hours. Match the form to the likely intensity profile of the event.
Practising the plan before race day
Gut training is not a phrase reserved for professional cyclists doing 120 g/hr in a Grand Tour. It applies to any rider trying to increase their in-race carbohydrate intake beyond what their gut currently tolerates. If you currently manage 40–50 g/hr without problems and want to move to 70–80 g/hr, add 10 grams per hour every two to three weeks of long training rides. The intestinal transporters adapt over weeks of consistent stimulus — the research is clear on this, and the adaptation is genuinely available to amateur riders, not just elites.
Build your plan on paper first. Write down the start time, feed zones if applicable, and what you will eat and drink at each 20–30 minute mark. Then execute it in training on a ride that mimics race conditions as closely as possible — similar duration, similar intensity profile, similar heat if you can manage it. Adjust based on what you learn. This is the part most riders skip, and it is the part that separates a fueling plan that survives contact with the race from one that falls apart at the first hard climb.
One practical tip: carry more than you think you will need. A spare gel in your jersey pocket is insurance against a longer neutral rollout, a longer race than expected, or simply missing a feed. The cost of carrying an extra 50 grams is negligible. The cost of running out of carbohydrate in the final hour is enormous.
Related reads
Sources
- Hearris MA et al. (2022). A step towards personalised sports nutrition: carbohydrate intake during exercise. Frontiers in Nutrition.
- Podlogar T, Wallis GA (2022). New horizons in carbohydrate research and application for endurance sports. Sports Medicine. link.springer.com
- Jeukendrup AE (2014). A step towards personalised sports nutrition: carbohydrate intake during exercise. Sports Medicine. PMC4008807
- Kienle A et al. (2025). A narrative review of the high-carbohydrate fueling revolution (≥100 g/h) in the professional peloton. Sports Medicine. link.springer.com
- PMC (2025). Under consumed and overestimated: discrepancies in race-day carbohydrate intake among endurance athletes. PMC12501108