Carbs Per Hour: How Much Fuel You Need During Exercise

Most athletes who fade at hour three made the mistake before they left the house. Carbohydrate during exercise is prescribed as grams per hour, and the right number moves with how long you will be out and how hard you intend to go. Guess low and the last hour costs you twenty minutes you cannot get back. Guess high, on a gut that has never seen that much sugar at once, and you spend the back half of the session negotiating with your stomach instead of racing.

The number is grams per hour, not grams per kilo

Almost everything else in sports nutrition scales to bodyweight. Protein, daily carbohydrate, fluid replacement: all per kilo. Carbohydrate during exercise breaks the pattern because of where the bottleneck sits. Absorption happens in the small intestine, and intestinal transporter capacity does not scale with how big you are. The reference review puts it flatly: the guidelines "are expressed in grams per hour of exercise and these figures are not corrected for body weight", because "there appears to be no correlation between BW and exogenous carbohydrate oxidation" (Jeukendrup, Sports Medicine, PMC4008807).

A 58 kg runner and a 92 kg rider out for the same three hours need close to the same hourly intake. Duration sets the band you belong in. Intensity decides where inside it you land.

The carbs per hour table

Find the row that matches the session you are about to do, not the session you wish you were fit enough to do. The second column is the target. The fourth column converts it into things you can put in a pocket, and the last column tells you what physiology the number is answering to.

Those bands trace the consensus. Small amounts including a mouth rinse for roughly 30-75 minutes, 30-60 g/h from one to two and a half hours, and up to 90 g/h beyond two and a half to three hours, with the high end requiring a mix of carbohydrate types rather than a single sugar (Jeukendrup, PMC4008807). If you want the totals to pack rather than the hourly rate, the race nutrition planner turns a finishing time into carbs, fluid and sodium for the whole day.

Why 60 grams an hour is a wall

Glucose crosses the intestinal wall on a sodium-dependent transporter called SGLT1. That transporter saturates at an intake of around 60 g/h. Past the saturation point, extra glucose does not become extra energy. It sits in the gut and pulls water in with it.

The ceiling is measurable. Exogenous glucose oxidation "will not rise above 1.0-1.1 g/min when only glucose is ingested during exercise", which is 60-66 grams an hour of usable fuel no matter how much more you swallow (Trommelen et al., Nutrients, PMC5331598).

Fructose uses a different door, GLUT5, and that door is still open when SGLT1 is full. Feed both at once and the ceiling rises. In that same controlled trial, glucose alone was oxidised at 0.96 g/min while glucose plus fructose reached 1.40 g/min, roughly 46 percent more fuel delivered from the same gut. Push harder still and the numbers keep climbing: 120 g/h in a 0.8:1 fructose to maltodextrin blend produced 1.51 g/min of exogenous oxidation across the final hour of a three-hour ride, against 1.29 g/min at 90 g/h in a 1:2 ratio (Podlogar et al., European Journal of Applied Physiology, PMC9560939).

This is the single most useful thing to know about fueling. Below 60 g/h, the carbohydrate type barely matters. Above it, type is the whole game.

Intensity moves you inside the band

Carbohydrate oxidation climbs with effort. A three-hour tempo ride burns fuel far faster than a three-hour social ride, so one row can mean 60 g/h for one athlete and 90 g/h for another. The review is explicit about the downward adjustment: "when the exercise intensity is low and total carbohydrate oxidation rates are low, carbohydrate intake recommendations may have to be adjusted downwards" (Jeukendrup, PMC4008807).

Practically: a six-hour zone 2 ride does not need 90 g/h. Sixty is plenty, and some of it should be food you can chew. A three-hour race at threshold does need it, and gets it in liquid and gel form because your stomach will not accept much else at that heart rate. If you track training stress score, the sessions carrying the highest TSS per hour are the ones to fuel at the top of the band.

What the top of the range buys, and what it does not

Higher intake changes measurable outcomes, though not always the ones people expect.

Twenty elite trail runners raced a mountain marathon on 60, 90 or 120 g/h. Twenty-four hours later, the 120 g/h group had held their jump height (a 1.19 percent change against declines of 11.33 and 9.66 percent), lost almost no half-squat strength (minus 2.35 percent against minus 15.30 and minus 13.84), and preserved high-intensity run capacity while both lower-intake groups fell by about 14 percent (Urdampilleta et al., Nutrients, PMC7400827). The headline there is recovery. Fueling is what lets you train again on Tuesday.

The counterweight comes from the 120 g/h laboratory work. The higher exogenous oxidation did not come with any further drop in how much of the body's own carbohydrate was burned, so the extra fuel did not spare stored glycogen the way theory predicts (Podlogar et al., PMC9560939). More carbohydrate in means more carbohydrate burned, not a bigger reserve at the finish. Treat 120 g/h as a specialist tool for a long, hard, important day on a gut you have already trained.

Turning grams into gels, bottles and real food

Numbers on a page are easy. Hitting them at kilometre 90 with cold hands is the hard part, so do the arithmetic at the kitchen table.

• A standard gel is 22-25 g. Three gels an hour is 66-75 g, so 90 g/h needs a fourth gel or a carbohydrate drink running alongside.
• Drink mix is where the volume hides. A 500 ml bottle at 40 g is a third of a 120 g hour and goes down without a chewing effort. Two bottles plus two gels clears 120.
• Solid food works below race intensity. A banana is roughly 25 g, a rice cake 20-30 g, a handful of dried dates 40 g or more. Save them for long easy efforts, where your stomach still has blood supply.
• Watch the concentration, not only the grams. Beverages with osmolalities above 500 mOsm/L "seemed to be associated with an increased incidence of symptoms" (de Oliveira et al., Sports Medicine, PMC4008808). A gel chased with water is a different drink from a gel taken dry.
• Pick a ratio and rehearse it. Ten cyclists tested fructose to maltodextrin at 0.5, 0.8 and 1.25. Mean exogenous oxidation ran 1.04, 1.14 and 1.05 g/min, and stomach fullness, cramping and nausea rose least on the 0.8 ratio, which also gave about 3.6 percent more peak power than the 0.5 (O'Brien and Rowlands, American Journal of Physiology, 2011).
• Set a timer. Every 20 minutes, take a third of your hourly target. Waiting until you feel empty means you are already an hour behind.

Fluid and sodium ride alongside the carbohydrate and get their own numbers. Work out your hourly loss with the sweat rate calculator, then read hydration tracking for athletes for what to do with the answer.

Where the number fails

The plan rarely fails because the target was wrong. It fails in execution.

• Starting at hour two. By the time you notice the deficit, absorption cannot catch you up. Start feeding inside the first 30 minutes of anything over two hours.
• Never rehearsing it. Athletes unaccustomed to taking fluid and food during exercise carry "a twofold risk of developing gastrointestinal symptoms" (de Oliveira et al., PMC4008808). Race day is a terrible laboratory.
• Jumping straight to the top row. The gut adapts, but over weeks. Build from 60 toward 90 across a training block, one long session at a time. The protocol lives in gut training and carb tolerance.
• Not counting at all. In a survey of 1,081 endurance athletes, only 21.6 percent monitored their training intake in grams per hour, and 67.6 percent went by gut feeling (Reinhard and Galloway, Frontiers in Nutrition, 2022). Most fueling plans are vibes.
• Assuming the stomach is the problem. Gastrointestinal complaints hit 30-50 percent of endurance athletes and 30-90 percent of distance runners (de Oliveira et al., PMC4008808). Often the fix is the drink concentration or the carbohydrate ratio, not the total.

FAQ

Do I need carbs on a 45 minute easy run?

No. Stored muscle and liver glycogen cover a 45-minute effort comfortably, so water is enough. Carbohydrate during short sessions is a habit borrowed from long-course racing where it belongs. The one exception is a short hard effort in a fasted state, where a carbohydrate mouth rinse can help through a central mechanism rather than by supplying fuel.

What is the difference between a 2:1 and a 1:0.8 glucose to fructose ratio?

Both mix two sugars that use separate intestinal transporters, which is what lets total intake climb past 60 g/h. The older 2:1 ratio pairs 60 g of glucose with 30 g of fructose to reach 90 g/h. The newer 1:0.8 blends push more fructose in, which supports higher intakes near 120 g/h and, in ratio-comparison work, produced less stomach fullness and cramping.

Can I hit 90 grams an hour with real food instead of gels?

On a long easy ride, yes. A banana, a rice cake and a bottle of mix will get you near 90 g without a single gel. At race intensity it becomes hard, because blood flow shifts away from the gut and chewing while breathing hard is unpleasant. Most athletes end up with food early and liquid plus gels once the effort lifts.

Does my bodyweight change how many carbs per hour I need?

Barely. The bottleneck is intestinal absorption capacity, which does not track bodyweight, and research finds no correlation between body weight and how much ingested carbohydrate you can oxidise. A light runner and a heavy rider doing the same duration at the same relative effort land on similar hourly targets. Duration and intensity are the levers that matter.

Will more carbs per hour make me faster, or only help me recover?

Both, with different confidence. Adequate fueling clearly protects performance in efforts past two hours by preventing the late-race fade. Intakes near 120 g/h have their strongest evidence in next-day recovery, where they preserved jump height and strength in trail marathoners. The effect on finishing time is less settled, and higher intake does not appear to spare your own stored glycogen.

How do I know if my gut can handle 90 grams an hour?

Test it in training, on a session that looks like your race in duration and intensity. Take your target rate from the start, split into doses every 20 minutes, and log what happened. Bloating, cramping or urgency inside the first hour means back off 15-20 g and rebuild over a few weeks. A clean long session at the target twice in a row means you are ready.

How Movement Rebels fits

Knowing your number is the easy half. Choosing which sessions to rehearse it on is coaching. The Movement Rebels AI coach reads every Garmin and Apple Health sync, so it sees the duration, the pace splits or per-lap power, and the training effect of the long ride you did on Saturday. It also sees the strength session you logged in the calendar on Thursday, two days ahead of it. Write your fueling plan into the note on that activity, or into Notes for your coach, and it becomes part of the picture the coach works from. When your resting heart rate drifts up and your HRV trend drops across a heavy block, the coach reads that as a fueling and recovery signal and pulls the following week back instead of stacking another long effort on top.

It also works backward from a date. Give it a race with a date and a target time and it builds a periodized arc to it, so each weekly plan knows how many weeks out you are and whether the week is a deload. Rehearse your race-day rate on the long sessions in the build weeks. Let the deload weeks stay easy.

Start at 60 g/h on your next three-hour session, take it every 20 minutes, and write down what your stomach did.