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Uri Carlson, registered dietitian and fuelling specialist associated with Skratch Labs, set Anthony a three-ride protocol on the Roadman 100km Saturday loop: 20g carbs per hour, 60g per hour, and 120-130g per hour. The results weren't what most people expect. More fuel doesn't automatically mean better numbers.
At 20g carbs per hour on a Zone 2 ride, Uri predicted heart rate decoupling in the second half, leg heaviness, and reduced focus. Not because 20g is dramatically low in isolation, but because Anthony was already running at 45g and cutting that in half compounds fast over three hours. The fix isn't eating more for the sake of it. Sixty grams per hour is the target for that kind of effort at 80-82kg, based on replacing around 50% of hourly calorie burn. That's your starting point, not a ceiling.
Overfueling is its own problem. At 120-130g per hour on a Zone 2 ride, your gut pulls water from circulation into the stomach to dilute the excess carbohydrate concentration. You get the sloshing, the nausea, the distraction. You have enough fuel to do the work but you're compromising the systems that let you do it. Uri also flagged something most riders miss: if you're calculating daily calories as base metabolic rate plus ride calories, you're double-counting. Your metabolic rate during the ride is already in the ride number. Subtract the hours you were on the bike from your 24-hour baseline before you add the two together.
If this is making you rethink how much you're eating on the bike, the episode on losing 9kg while eating more covers the full picture of fueling for body composition. And the Tim Podlar episode on how pros get lean goes deeper on the daily calorie calculation mistake Anthony mentions here.
Anthony Walsh's three-ride fueling experiment compared 20g, 60g, and 120-130g carbohydrates per hour on his standard Saturday 100km loop at approximately 230W average — designed by registered dietitian Uri Carlson to isolate fueling effect from training stimulus.
Source: Anthony Walsh and Uri Carlson protocol design
Under-fueling during sustained Zone 2 efforts (sub-half of baseline intake) typically produces measurable heart-rate-to-power decoupling in the second half of the ride, plus subjective lightheadedness, nausea, and intrusive food preoccupation.
Source: Uri Carlson, registered dietitian and Skratch Labs fueling specialist
Recommended intra-ride carbohydrate intake varies dramatically across authoritative sources — Alex Wild and Cameron Jones (Unbound winner) cite 200-220g/hour, while Dr Tim Podlogar (Tudor Pro Cycling) caps amateur absorption at ~90g/hour — illustrating the field's lack of consensus on optimal dose.
Source: Anthony Walsh, citing competing nutritionist sources
Long-term low-carbohydrate riding may produce metabolic adaptations (improved fat oxidation rates, modified liver glycogen availability) that reduce the relative penalty of further under-fueling — a key individual variable Carlson identifies as confounding generic fueling guidance.
Source: Uri Carlson, on the Roadman Cycling Podcast
“If you have too much carbohydrate in your gut that your body is not utilizing because it's too much and it doesn't need it, 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.”
“We can take maybe three of those and average out the calorie burn over three of those 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.”
“When you are consuming a sports drink with electrolytes and sugar in it, the sugar can help to get more water molecules across your intestine.”
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