Reviewed for accuracy: This article references the published carbohydrate-oxidation research of Prof. Asker Jeukendrup, the 28-day adaptation study by Cox and colleagues (J Appl Physiol, 2010), and the high-intake fuelling work of Tim Podlogar. The intake bands described are training and performance targets, not medical recommendations. Riders with diabetes, gut conditions or other clinical concerns should consult a sports dietitian.
Here's what nobody tells you about hitting 120g of carbohydrate per hour: your legs were ready years ago. The thing holding you at 60g is your gut. It's the bottleneck — and like every other system in cycling, it adapts to the load you put on it.
The good news is that this is the most fixable problem in nutrition. You don't need a different metabolism or a pro contract. You need a few weeks of deliberate practice, the right products, and the discipline to ramp slowly instead of force-feeding yourself on race morning and wondering why your stomach quit at 80km.
Let me break down how the gut actually adapts, the protocol that gets you to 90-120g per hour, and the mistakes that keep most amateurs stuck.
The short answer
The gut is a trainable organ. Repeated exposure to high carbohydrate intake during exercise increases the number of transporters lining your intestine, speeds up how fast your stomach empties, and quietens the symptoms that make high intake miserable. A rider who tops out at 60g per hour can usually build to 90g per hour, and often the full 100-120g, over 6 to 12 weeks. You ramp the dose by about 10g per hour every two to three weeks, you do it on real long rides at race effort, and you do it with the exact gels and drink mix you plan to race on. That's the whole game.
Why your gut is the limiter, not your legs
When you ride hard for hours, your muscles can oxidise carbohydrate at rates well above what most amateurs ever feed them. The ceiling on performance in a long event is rarely "my muscles can't use the fuel." It's "I can't get the fuel in and absorbed fast enough."
The absorption step is the wall. Carbohydrate you swallow has to empty from the stomach, then cross the intestinal wall into the blood before a single gram reaches a working muscle. That crossing happens through specific transporter proteins. Glucose uses one called SGLT1. Fructose uses a different one called GLUT5. This is the basis of Asker Jeukendrup's decades of work on multiple transportable carbohydrates — and it's why every serious gel and drink mix above 60g per hour is built on a roughly 2:1 glucose-to-fructose ratio. Glucose alone saturates SGLT1 at about 60g per hour. Add fructose and you open a second lane, lifting the practical ceiling to around 90g per hour, and beyond with training.
The key word is training. The density of those transporters is not fixed. That's the entire reason gut training works.
What the science actually shows
The landmark study is Cox and colleagues, published in the Journal of Applied Physiology in 2010. They took endurance cyclists, put one group on 28 days of high daily carbohydrate intake during training, and measured how much ingested carbohydrate the body actually burned during a ride afterwards. The high-carb group raised their exogenous carbohydrate oxidation — they got measurably better at using the fuel they swallowed. Same legs, same fitness, but the gut had learned to get more fuel through to the muscle.
The mechanism research that followed points in the same direction. Repeated high carbohydrate exposure upregulates SGLT1 expression in the gut, improves gastric emptying, and reduces the gastrointestinal symptoms — the bloating, the cramping, the urgency — that wreck high-intake fuelling in an untrained gut. Ricardo Costa's group at Monash University has built much of the practical "train the gut" framework on exactly this, showing that the symptoms themselves are trainable: the same dose that floors you in week one is tolerable by week six.
Tim Podlogar, whose work sits right at the top end of this — studying intakes of 120g per hour and beyond — has shown the body can handle and use far more than the old textbooks claimed, provided the gut is prepared for it. The pros eating 120g per hour in a Grand Tour aren't freaks of nature. They're the product of years of progressive exposure.
The protocol that works
This is straightforward progressive overload. The same principle that builds your aerobic fitness builds your gut.
Weeks 1-2 — find your floor. On a long ride at genuine race effort, fuel at the intake you currently tolerate without distress. For most amateurs who haven't trained this deliberately, that's 50-60g per hour. Don't guess it — ride it and feel it. This is your starting line.
Weeks 3-4 — add 10g per hour. Bump to 60-70g per hour. Use the actual products you intend to race with, at a 2:1 glucose-to-fructose ratio. Hit this dose on two to three long rides across the fortnight, not once.
Weeks 5-6 — add another 10. You're at 70-80g per hour now. If symptoms appear, adjust the format before you adjust the dose — a more dilute drink, a switch from gel-and-drink to bar-and-drink, more fluid alongside the carbohydrate. The gut often tolerates the same grams delivered differently.
Weeks 7+ — keep ramping to target. Most amateurs reach 90g per hour reliably across a 6-12 week block. Riders building toward a long, hard event — a hilly sportive, a stage race, an ultra — keep going toward 100-120g if the event demands it.
The non-negotiables: real long rides, not five-minute kitchen experiments. Race effort, because intensity shunts blood away from the gut and changes everything — a dose that's fine at Zone 2 can fail at threshold. The exact products you'll race on. And enough fluid, because carbohydrate needs water to move. A concentrated gel with no drink behind it sits in your stomach like a stone, which is why gut training and your electrolyte and sweat-rate plan are really two halves of the same bottle — the sodium that drives fluid absorption is part of getting the carbohydrate moving too.
The in-ride fuelling calculator will set your per-hour carbohydrate, fluid and sodium targets for a given ride so you've got a number to ramp toward instead of guessing.
The mistakes that keep amateurs stuck
Only practising on race day. This is the big one. You read that pros eat 120g per hour, you buy a box of gels, you cram them in on event morning, and your gut — which has been fed 40g per hour all winter — revolts at 60km. The gut was never trained. Race day is for executing a rehearsed plan, not auditioning a new one.
Ramping too fast. Jumping from 60 to 100g per hour in one ride doesn't accelerate the adaptation. It just makes you ill and teaches you to fear fuelling. Ten grams every two to three weeks feels slow. It's the pace that sticks.
Training on one product, racing on another. Different brands use different osmolalities, ratios and flavourings. A gut rehearsed on one gel can still rebel against another. Pick your race products early and train the gut on those specifically.
Forgetting fluid. Carbohydrate concentration in the gut drives a lot of the distress. Adequate fluid dilutes it and helps it move. Most "my stomach can't handle gels" problems are really "my stomach can't handle gels without water."
Trying to train the gut in a deficit. If you're eating in a calorie deficit to lose weight, you're fighting two adaptations at once and winning neither. Gut training is a fuelling adaptation — it wants carbohydrate available. Do your gut work in a fuelled phase, not in the middle of a cut. This is the same fuel-for-the-work-required logic that underpins the rest of the nutrition cluster.
How this fits the bigger picture
Gut training is the natural sequel to the carbohydrate-per-hour question. Once you've worked out the number you should be eating for an event, gut training is how you make that number tolerable. The two go together: the target tells you where to aim, the gut work gets you there. And tolerating that number is precisely what keeps you off the rocks — a gut that can absorb 90g an hour is your best insurance against bonking late in a long ride, because the fuel actually reaches the blood instead of sitting in your stomach.
It also changes how you read the headline pro numbers. When Ben Healy's fuelling strategy or a World Tour rider's 120g-per-hour plan gets quoted, the right response isn't "I should do that tomorrow." It's "that's a trained capacity, and here's the eight-week ramp that earns it." Dr. David Dunne and the nutritionists we've had on the podcast make the same point repeatedly — the dose is the easy part to copy and the hardest part to actually tolerate.
This is all part of the broader cycling nutrition system: set the target, train the gut, fuel the work, recover properly. None of it is complicated. It just takes a few weeks of doing the unglamorous thing — eating on the bike, on purpose, slightly more than was comfortable last week — until the gut catches up to the legs that were ready all along.
If you've got a specific question — your own ramp for a target event, what to do when one product keeps upsetting you, or how to rebuild tolerance after the off-season — join the community and talk it through with riders working on exactly the same thing, drawing on everything we've learned from Tim Podlogar, Dr. David Dunne and the rest of the nutrition guests.