Most cyclists know they should eat on the bike. Far fewer know how much, how often, or why their stomach rebels halfway through a long ride. The gap between knowing "fuel matters" and actually executing a fueling strategy is where most amateur riders lose performance — not from a lack of fitness, but from a lack of calories arriving at the right time in the right form.
On-the-bike nutrition has changed considerably in the last five years. Professional teams now routinely push intake above 90 grams of carbohydrate per hour, and some riders hit 120 grams in Grand Tour stages. That doesn't mean you need to chase those numbers tomorrow. But the science behind those practices filters down to every level of the sport, and understanding the principles helps you ride longer, recover faster, and avoid the dreaded bonk without turning your stomach into a war zone.
Why your body runs out of fuel faster than you think
Your muscles store glycogen — the body's quick-access energy currency — in limited quantities. A well-fed cyclist starts a ride with roughly 400 to 500 grams of stored glycogen spread across muscles and liver, which translates to about 90 to 120 minutes of moderate-to-hard riding before those stores deplete significantly. Once glycogen runs low, power output drops, perceived effort spikes, and concentration fades. That's the bonk: not a gradual decline, but a sharp wall where everything suddenly costs twice as much effort.
Fat oxidation picks up some of the slack at lower intensities, and a well-trained aerobic system is better at burning fat. But fat cannot fuel high-intensity efforts the way carbohydrate can. Even at moderate endurance pace, carbohydrate still contributes a substantial share of the energy mix. The practical takeaway is simple: if your ride is longer than about 90 minutes or includes any real intensity, eating on the bike isn't optional. It's the difference between finishing strong and limping home.
How many carbs per hour you actually need
Current sports science recommends a sliding scale based on ride duration and intensity. For rides between one and two hours at moderate effort, 30 to 60 grams of carbohydrate per hour is enough to top up glycogen stores and maintain blood sugar. Once you cross the two-hour mark — or if the intensity is high from the start — the target shifts to 60 to 90 grams per hour. That higher range requires a mix of glucose and fructose, because the gut has separate transport mechanisms for each sugar and a single transporter maxes out around 60 grams per hour on its own. Combining glucose and fructose at roughly a 1-to-0.8 ratio has been shown to increase exogenous carbohydrate oxidation rates by up to 65 percent compared to glucose alone, reaching peak oxidation of about 1.75 grams per minute instead of the old ceiling of 1 gram per minute.
For most amateur cyclists doing rides of two to four hours, aiming for 60 to 80 grams per hour is a sensible target. You don't need to hit 90 or 120 grams unless you're racing at threshold for extended periods. More important than the exact number is consistency: eating small amounts every 20 to 30 minutes is far better than cramming a big feed at the hour mark and hoping your gut cooperates. Think of it as drip-feeding energy rather than bolus dosing it. A gel every 25 minutes or a few swigs of a concentrated drink mix at regular intervals keeps blood sugar stable and avoids the spike-and-crash pattern that leads to both nausea and energy dips.
Why your stomach fights back (and how to fix it)
Gastrointestinal distress during exercise is remarkably common — studies report that 30 to 90 percent of endurance athletes experience some form of stomach trouble during hard or prolonged efforts. Symptoms range from mild bloating and fullness to nausea, cramping, and worse. Most of it comes down to two factors: blood flow redistribution and carbohydrate malabsorption. When you're riding hard, blood shifts away from the gut toward working muscles, which slows digestion. Meanwhile, dumping a large bolus of carbohydrate into a sluggish gut overwhelms the intestinal transporters and draws water into the intestine by osmosis, producing that familiar sloshing discomfort.
The fix is gut training, and the evidence supports it clearly. A 2023 systematic review found that repeated exposure to carbohydrate intake during exercise — practised over two to four weeks — reduces symptoms and increases tolerance to higher intake rates. The protocol is straightforward: during your regular training rides, practise consuming the same foods and drinks you plan to use on longer rides or event days. Start at a comfortable intake, say 40 grams per hour, and increase by 10 grams per hour every week or two until you reach your target. Your gut adapts by upregulating transporter expression and improving gastric emptying, much like any other training stimulus. Race day is not the time to try a new gel brand, a higher intake rate, or a different drink concentration. Practise everything in training, and your gut will thank you when it counts.
A few practical habits reduce GI risk further. Avoid high-fibre and high-fat foods in the two to three hours before a ride, because both slow gastric emptying. Choose carbohydrate sources you've tested — gels, drink mix, rice cakes, dates, or whatever agrees with you — and rotate them to avoid flavour fatigue on long rides. Keep sipping rather than gulping. And if you feel the early signs of stomach distress, back off the intensity slightly for five minutes. Even a small reduction in exercise intensity redirects blood back to the gut and can settle things quickly.
Hydration and sodium: the other half of the equation
Fueling and hydration are two sides of the same coin, and neglecting either one undermines the other. Dehydration above about two percent of body mass impairs endurance performance measurably, and most cyclists sweat between 0.5 and 2.0 litres per hour depending on intensity, temperature, and individual physiology. The goal isn't to replace every drop of sweat — that's impractical and can actually cause problems — but to limit fluid loss enough that performance doesn't slide. A good starting point is 400 to 800 millilitres per hour, adjusted upward in heat and downward in cool conditions or on easy rides.
Sodium deserves more attention than most riders give it. Sweat contains sodium, and losing it without replacement can contribute to cramping, fatigue, and reduced fluid absorption in the gut. Current recommendations for endurance exercise beyond two hours suggest 250 to 500 milligrams of sodium per hour from a combination of sports drink and food. Athletes with particularly salty sweat — you'll recognise it by the white residue on your kit after a hot ride — may need more. Adding a sodium-containing electrolyte mix to your bottles serves double duty: it replaces what you lose in sweat and it improves the palatability and voluntary intake of fluid, which means you actually drink more. Plain water is fine for short, easy rides, but once duration or intensity rises, electrolytes earn their place.
Integrating hydration into your fueling plan simplifies everything. A concentrated carbohydrate drink mix in one bottle and plain water or a lighter electrolyte mix in the second bottle gives you flexibility to adjust carbohydrate and fluid intake independently. On hot days you drink more of the water bottle; on cooler days you lean on the concentrated bottle. That two-bottle system works for most rides up to three hours. Beyond that, you need a plan for refills — either a cafe stop, a carried bidon, or a support car if you're lucky enough to have one.
Getting your fueling and hydration dialled in is one of the highest-return investments you can make as a cyclist, because it costs no extra fitness. You already have the engine; on-the-bike nutrition just makes sure it has fuel. If you want a plan that factors your ride duration, intensity, and weekly schedule into a coherent structure — including when and how hard to ride — LeCoach builds your week around your real availability and goals. And if you're already eating on the bike but wondering how to structure the rides themselves, the post on time-crunched cycling training covers the training side of the equation.
Sources
Jentjens RL, et al. "High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise." British Journal of Nutrition, 2005.
Hearris MA, et al. "A Narrative Review of the High-Carbohydrate Fueling Revolution (≥ 100 g/h) in the Professional Peloton." Sports Medicine, 2025.
Gaskell SK, et al. "The Effect of Gut-Training and Feeding-Challenge on Markers of Gastrointestinal Status in Response to Endurance Exercise: A Systematic Literature Review." Sports Medicine, 2023.
Jeukendrup AE. "Multiple Transportable Carbohydrates and Their Benefits." Gatorade Sports Science Institute, Sports Science Exchange.