On-Bike Fueling: How to Eat During a Ride

Bonking is the endurance athlete's nightmare: your legs turn to concrete, your brain fogs, and every pedal stroke feels like moving through wet sand. The cause is almost always the same — you ran out of fuel. On-bike fueling is not a nice-to-have accessory for long rides. It is a core performance skill that separates riders who finish strong from those who crawl home. Get it right and you unlock hours of sustainable power. Get it wrong and no amount of fitness will save you.

Why Your Body Needs Fuel on the Bike

Your body stores carbohydrate as glycogen in your muscles and liver. The total reservoir is approximately 1,600–2,000 kcal — enough to sustain hard riding for roughly 60–90 minutes at threshold intensity, or 2–3 hours at a moderate zone 2 pace. Once those stores run low, performance drops precipitously. This is the bonk.

Your body can also burn fat for fuel, and fat stores are effectively unlimited (even a lean athlete carries 40,000+ kcal of body fat). But fat oxidation has a rate ceiling. Even highly trained, fat-adapted athletes can oxidize fat at only about 1.0–1.5 g/min, which yields roughly 540–810 kcal/hour. At moderate-to-high intensities — anything above about 65% of FTP — your energy demand exceeds what fat alone can supply. The gap must be filled by carbohydrate.

This is the fundamental energy problem of endurance cycling: you burn carbohydrate faster than your body can replace it from fat. The only solution is to eat carbohydrate during the ride to supplement your glycogen stores and delay or prevent their depletion.

How Many Carbs Per Hour — The Definitive Guide

The amount of carbohydrate you need depends on ride duration and intensity. Sports nutrition research has converged on clear, evidence-based tiers. These recommendations come from the work of Asker Jeukendrup and the International Olympic Committee consensus statements on sports nutrition.

These are targets, not starting points. If you have never fueled deliberately on the bike, start at the lower end and build up over weeks. Your gut is trainable — more on that below.

Glucose + Fructose: The Dual Transporter Advantage

For decades, the maximum recommended carbohydrate intake during exercise was 60 g/hour. This ceiling exists because of a single bottleneck: the SGLT1 transporter in your small intestine, which absorbs glucose (and maltodextrin, which is just a glucose polymer). SGLT1 maxes out at approximately 60 g of glucose per hour. Consuming more glucose beyond this point does not increase absorption — it just sits in your gut, draws in water, and causes bloating and GI distress.

The breakthrough came from Asker Jeukendrup's research showing that fructose uses a completely different transporter: GLUT5. Because GLUT5 operates independently of SGLT1, adding fructose on top of glucose allows an additional 30–60 g/hour of carbohydrate absorption. Combined, these two pathways can deliver 90–120 g of total carbohydrate per hour.

The latest research from Jeukendrup's group recommends a glucose-to-fructose ratio of 1:0.8, which maximizes absorption from both transporters. Many commercial products now use this ratio. If you are using gels or drink mixes that contain only glucose or maltodextrin, you are capping your absorption at 60 g/hour regardless of how much you consume.

This is why ingredient labels matter. Look for products that list both maltodextrin (or glucose) and fructose. Avoid products with only a single sugar source if you plan to fuel above 60 g/hour.

What to Eat on the Bike

There is no single “best” on-bike food. The best fueling strategy uses a mix of sources matched to your intensity, duration, and personal tolerance. Here is how the main options compare.

Homemade Options That Work

You do not need to buy expensive commercial products to fuel well. Maple syrup diluted with water and a pinch of salt makes a simple, effective carb drink (about 52g carbs per 60ml of syrup). Rice cakes made with sushi rice, a thin layer of jam, and a pinch of salt are what many WorldTour teams use. Dates stuffed with a small amount of nut butter deliver roughly 18g of carbs each. The key is testing these options in training so you know exactly what your stomach can handle.

A practical race-day approach for a 4-hour sportive might look like: one concentrated drink mix bottle (80g carbs), topped up with gels every 20–25 minutes (25g each), plus a bar in the first hour. That gets you comfortably above 90g/hour.

When to Start Fueling

One of the most persistent mistakes in endurance nutrition is waiting too long to eat. By the time you feel hungry on the bike, your glycogen stores are already significantly depleted and your blood glucose is dropping. Catching up from this deficit is extremely difficult because intestinal absorption has an upper limit — you simply cannot shovel carbs in fast enough once you are behind.

The rule is simple: start fueling within the first 20–30 minutes of any ride that will last longer than 75 minutes. Take your first gel, your first sips of drink mix, or your first bites of a bar before you feel any need for it. Then set a repeating timer on your bike computer or watch for every 20 minutes. Every time it goes off, eat or drink something. This mechanical, non-negotiable rhythm removes decision-making from the equation and ensures steady carbohydrate delivery throughout the ride.

Think of it like stoking a fire. Small, frequent additions of fuel keep the fire burning steadily. Dumping a huge amount of wood on a dying fire produces smoke and chaos. Your digestive system works the same way — small, regular feeds are absorbed far more efficiently than large, infrequent boluses.

How to Train Your Gut

If you have never consumed 90g of carbohydrate per hour on the bike, your gut is not ready for it. Gastrointestinal tolerance is trainable, and this is one of the most under-appreciated aspects of endurance performance. Research shows that the intestinal transporters SGLT1 and GLUT5 are upregulated in response to regular high-carbohydrate intake — meaning the more you practice eating on the bike, the more efficiently your gut absorbs carbs.

Start at 40g per hour during training rides. If that is comfortable after two weeks, increase to 50g. Then 60g. Continue adding 10g per hour every 1–2 weeks until you reach your target race-day intake. This progressive overload mirrors how you would increase training volume — gradually and systematically.

Some practical tips for gut training: practice during training rides at the intensity you expect on race day (fueling at zone 2 is much easier than fueling at tempo or threshold). Include high-carbohydrate meals in your daily diet on hard training days, as this also helps upregulate intestinal transporters. Avoid high-fiber and high-fat foods in the 2–3 hours before a training session where you plan to practice fueling — fiber and fat slow gastric emptying and increase GI distress risk.

And the cardinal rule: never try a new fueling strategy on race day. Everything you consume during a race should have been tested multiple times during training.

Hydration During Rides

Fueling and hydration are intertwined but distinct problems. You can nail your carbohydrate intake and still perform poorly if you are dehydrated. Conversely, drinking too much plain water without electrolytes can cause hyponatremia — a dangerous drop in blood sodium concentration that can lead to confusion, seizures, and in extreme cases, death.

Aim for 500–750 ml of fluid per hour, adjusting upward in hot or humid conditions. Your sweat rate is individual — you can estimate it by weighing yourself before and after a ride (each kg lost equals roughly one liter of sweat). Most athletes underestimate their sweat rate, especially in the heat.

Sodium is the critical electrolyte. 500–1,000 mg of sodium per hour is a good starting range, with heavier sweaters and hot-weather riding at the upper end. If you notice white salt stains on your jersey or helmet straps after a ride, you are a salty sweater and should target the higher end of this range. Sodium maintains plasma volume, supports nerve function, and aids glucose absorption through the SGLT1 transporter — sodium and glucose are co-transported, so adequate sodium actually improves carbohydrate uptake.

Use electrolyte tablets or sodium-containing drink mixes rather than plain water. If you use a concentrated carb drink in one bottle, carry a second bottle with an electrolyte solution or plain water to manage thirst independently of your carb intake.

Race Day Fueling Strategy

Race nutrition starts 48 hours before the gun goes off. Here is the complete timeline:

48 Hours Before: Carb Loading

Increase carbohydrate intake to 10–12 g/kg of body weight per day for two days before your event. For a 75 kg rider, that is 750–900g of carbohydrate per day. This saturates your glycogen stores to their maximum capacity. Focus on easily digestible, low-fiber carb sources: white rice, pasta, bread, potatoes, pancakes, fruit juice. This is not the time for whole grains and vegetables.

3 Hours Before: Pre-Race Meal

Consume 2–3 g/kg of carbohydrate in your final pre-race meal, roughly 3 hours before the start. Keep fat and fiber low to ensure gastric emptying is complete before you start riding. A classic pre-race meal: white rice with a small amount of chicken, or oatmeal with banana and honey. Avoid anything you have not eaten before a hard ride previously.

During the Race: Execute Your Plan

Start fueling immediately — within the first 15–20 minutes. Target 90–120g of carbohydrate per hour using the dual-fuel (glucose + fructose) sources you have practiced in training. Set a timer. Eat mechanically, on schedule, whether you feel hungry or not. Front-load your solid food in the first half of the race when intensity is typically lower and your stomach handles solid food better. Shift to gels and drink mix in the second half when intensity climbs.

One final rule that cannot be overstated: nothing new on race day. Not a new gel brand, not a friend's drink mix, not the nutrition provided at aid stations (unless you have tested it). Race day is execution, not experimentation.

Common Fueling Mistakes

These are the errors that derail otherwise well-prepared riders. Almost all of them are avoidable with planning and practice.

The under-fueling mistake deserves special attention. Many cyclists, particularly those trying to lose weight, deliberately restrict calories during rides. This is counterproductive. Training in a glycogen-depleted state impairs workout quality, blunts adaptation, increases muscle protein breakdown, and raises cortisol. If fat loss is a goal, manage your caloric deficit in the hours you are not training. On the bike, fuel the work.

The other mistake worth emphasizing is source diversity. At 90+ g/hour, consuming everything as gels is a recipe for nausea. Splitting your intake across drink mix, gels, and solid food distributes the osmotic load across your gut and reduces the risk of any single source overwhelming your stomach. A practical split: 40–50% from drink mix, 30–40% from gels, and 10–20% from solid food in the early hours.

Putting It All Together

On-bike fueling is a trainable skill, not an innate talent. The athletes who fuel best are not the ones with the strongest stomachs — they are the ones who have practiced systematically, tested their products, and built their gut tolerance over months. Start with the basics: know your target carbohydrate intake for the ride duration, use dual-fuel sources (glucose + fructose) for anything above 60g/hour, begin eating within the first 20 minutes, and set a timer to eat every 20 minutes after that.

Nail these fundamentals and you will ride longer, harder, and more consistently than you ever have before. Ignore them and no amount of interval training, threshold work, or aerobic base will compensate for the hole in your tank.