The dominant message in cycling nutrition for the last few years has been simple: eat more. Train your gut, push the carbs per hour, chase the pro numbers. It's mostly been a useful correction, because most amateurs under-fuel. But Uri Carlson, a registered dietitian who fuels endurance athletes for a living, came on the podcast to add the other half of the sentence. There's such a thing as too much, and over-fuelling has consequences most riders don't understand.
Her framing — under, over, optimal — is the right way to think about it. Fuelling isn't a dial you turn as high as your stomach will allow. It's a range you're trying to land inside, and missing it in either direction costs you.
What over-fuelling actually does
Most riders can describe the feeling of over-fuelling even if they can't explain it: the sloshing stomach, the bloated heaviness, the sense that the last gel is just sitting there. Carlson explained the mechanism, and it’s useful to picture.
"If you have too much carbohydrate in your gut that your body is not utilising, because it's too much and it doesn't need it," she said, "your gut can actually pull water from circulation into your stomach to water down that concentration of carbohydrate — because it wants to have equal concentration on both sides. So you might get a little bit of GI upset, you might get that kind of sloshy stomach feeling, or that over-full feeling."
This is osmosis doing exactly what it always does. A very concentrated slug of carbohydrate sitting in your stomach pulls water across the gut wall to dilute it toward balance. That water comes from your circulation — the very blood volume you need out at your working muscles and skin. So over-fuelling doesn't just make you uncomfortable; it can actively work against you, drawing fluid into your gut and leaving it sloshing there instead of doing its job. It's a big part of the GI distress that wrecks so many long rides, and it explains why piling in more carbohydrate when you already feel full makes everything worse, not better.
It also reframes the gut-training arms race. Yes, you can train your gut to absorb more, and for racing that's worth doing. But there's a real ceiling on any given day, and blowing past it doesn't bank extra energy — it parks undigested fuel in your stomach and pulls water in after it. More is only better up to the point your body can actually use it.
Finding your optimal range
So if maximum isn't the target, what is? Carlson offered a concrete way to find your personal starting point, built around your own ride data rather than a generic number.
"We can take maybe three of those and average out the calorie burn over three of those," she said, "to get a low-end range and a high-end range. And then we want to aim to replace around 50% of those calories burned per hour. And that's a great baseline to start with, to kind of create a starting point in the first place."
Break that down, because it’s a method you can actually use. Take a few similar rides — three is plenty — and look at the calories your computer estimates you burned. Averaging across them gives you a realistic range rather than relying on one possibly-fluky number. Then aim to replace roughly half of that burn, per hour, with fuel on the bike. You're not trying to match your expenditure calorie-for-calorie — that's neither possible nor necessary, because your body carries substantial stored fuel. You're topping up enough to protect your glycogen and keep the work sustainable, which lands at around half for most riders. From there, our carbohydrate-per-hour guide and in-ride nutrition guide help you translate the calories into actual grams of carbohydrate and real food.
The beauty of the 50%-of-burn baseline is that it's personal by construction. A big rider grinding out a hilly four hours burns far more than a light rider spinning an easy two, and this method scales to each of them automatically. It starts you from your own physiology rather than a number copied off a pro.
Then make it yours
Carlson is emphatic that the 50% figure is a starting point, not a prescription, and this is where the under/over/optimal framing pays off. Once you have a baseline, you adjust based on the two things that actually matter: how your gut tolerates it, and how you perform.
If you're fuelling at your baseline and finishing rides hollow, fading badly in the final hour, or never quite recovering, you're probably under — nudge the intake up. If you're getting the sloshy stomach, the bloat, the GI grumbling Carlson described, you're over — back it off, or pair it better with your fluid and electrolyte intake so the concentration in your gut stays manageable. Optimal is the zone in between, where you arrive at the end with fuel still in the tank and a stomach that never became the story of the ride.
That zone is individual, and it shifts with intensity, heat, and how trained your gut is. The point isn't to find one magic number and defend it forever. It's to know your own range, recognise the signals of being under or over, and steer toward the middle. The rider who masters that will out-fuel the rider chasing the biggest possible number every single time — because they'll actually absorb what they take in, instead of carrying it around as ballast.
Carbs and fluid are the same problem
One reason the over-fuelling mechanism matters so much is that it ties carbohydrate and hydration together in a way most riders treat as separate. Because the gut pulls water to dilute an over-concentrated slug of carbohydrate, your carb rate and your fluid intake aren't two independent dials — they interact. Take in a lot of concentrated carbohydrate without enough fluid and you intensify the water-into-gut problem; the carbohydrate has nothing to dissolve into and sits there pulling fluid from your blood.
The practical upshot is to think about concentration, not just totals. If you're pushing your carbohydrate rate up — for a long event, say — your fluid and electrolyte intake usually needs to rise with it, so the mixture reaching your stomach stays dilute enough to absorb. Riders who get the sloshy, queasy feeling are often not simply eating too much; they're eating too much relative to what they're drinking. Matching the two is frequently the fix, and it's why drink mixes are formulated at particular concentrations rather than left to chance.
A worked example
To make the 50% method concrete, picture a rider whose computer says they burn roughly 700 calories an hour on their typical hard three-hour ride, averaged across a few of them. Half of that is 350 calories an hour to aim for on the bike. Since carbohydrate carries about 4 calories a gram, that's in the region of 80 grams of carbohydrate an hour — which, conveniently, lands right in the sensible range for a long, hard ride and roughly two-thirds of the way toward race-level fuelling.
From there it's a feel-and-adjust loop. Ride at that rate for a few sessions. Finishing strong with a settled stomach? You've found your range. Fading late and hollow? Edge it up toward 60% of burn. Getting the sloshy gut Carlson described? Back toward 40%, or drink more alongside it. The number isn't sacred — it’s a starting line you refine into something that’s actually yours, which is the whole point of fuelling by your own data rather than someone else's headline figure.
The takeaway
Carlson's message is a healthy corrective to "more is better." Under-fuelling empties you; over-fuelling pulls water into your gut and leaves you sloshing and queasy; optimal is a personal range you find and refine. Start by replacing about half the calories you burn per hour, estimated from a few real rides, then listen to your gut and your legs and adjust. Fuelling well isn't about eating the most. It's about hitting the range your body can actually use — and that number has your name on it, not a pro's.
Hear the full conversation with Uri Carlson on the Roadman podcast. For the practical detail, read our in-ride nutrition guide, and bring your fuelling questions to the community on Skool.