NutritionAnswer

HOW DO I TRAIN MY GUT TO TAKE MORE CARBS?

By Anthony WalshRoadman CyclingUpdated 26 May 2026

WHO THIS IS FOR

IS THIS YOU?

The racer chasing 90g/hr or higher intake

You want to fuel at pro-level rates for racing but know your gut is not ready for it yet.

The sportive rider with stomach problems on long rides

You have tried taking more food and ended up with GI distress in the back third of rides.

THE ROADMAN VIEW

The gut is trainable. That is the single most important thing to understand about high carbohydrate fuelling, and it is what makes the pro 120g/hr number possible for them but not for an untrained amateur who walks in cold. Anthony has covered this with Dr Sam Impey on the podcast — the transporters that move glucose and fructose from your gut into your bloodstream adapt under stimulus, just like a muscle adapts to resistance training.

The process is not fast. Four to six weeks of deliberate, progressive practice on training rides is the minimum to build meaningful absorption capacity. The protocol: pick a 2:1 glucose-to-fructose product, start at whatever you can currently tolerate without issues, and add 10–15g per hour every two to three weeks. The gut gives you honest feedback — nausea, bloating, or cramping means you have jumped too far. Back off one step.

The mistake most riders make is thinking gut training happens automatically through general riding. It does not. You need to specifically practise high intake on rides long enough to matter, using products that match the glucose-fructose ratio. An easy 45-minute spin with a single gel trains nothing. A three-hour ride where you systematically hit 80g/hr every week for a month trains a great deal.

EXPERT EVIDENCE

WHAT THE EXPERTS SAY

Dr Sam ImpeyWorld Tour nutritionist
High carbohydrate absorption capacity is an adaptation, not a given. The intestinal transporters that handle glucose and fructose — SGLT1 and GLUT5 — upregulate in response to regular high-carbohydrate intake. Riders who consistently practise fuelling at target race rates for four to six weeks measurably improve their absorption ceiling.
Hear it: Why Pros' 120g Carb Rule Fails Amateurs | Roadman Cycling
Fuelling experiment — under vs optimal vs overRoadman podcast — real-world fuelling test
The contrast between under-fuelled and optimally fuelled riding shows clearly that the ceiling for most amateurs is not physiological — it is a trained gut limitation. Riders who have practised taking 90g/hr regularly can perform at that level; those who have not almost always experience GI distress before they hit that target.
Hear it: Under vs Optimal vs Overfueling on the Bike | Roadman Cycling Podcast

PRACTICAL APPLICATION

DO THIS WEEK

Establish your current baseline
On your next two-hour-plus ride, take 60g of carbohydrate per hour using a 2:1 glucose-fructose product and note any GI response. If all is comfortable, that is your starting point. If even 60g causes issues, drop to 45g and build from there.
Add 10–15g per hour every two to three weeks
Once you are consistently comfortable at a level for two to three long rides, add 10–15g/hr in the next block. At 60g → 75g → 90g, building over 6–9 weeks. Each step should feel unremarkable before you take the next one.
Use the right product ratio
Above 60g/hr, you need both glucose and fructose to use two different gut transporters. A 2:1 glucose-to-fructose ratio — found in many dedicated endurance products — is the evidence-backed standard. Using glucose-only gels at 90g/hr is a reliable way to cause GI distress regardless of your training.

COMMON MISTAKES

WHAT CYCLISTS GET WRONG

MISTAKEJumping from 60g/hr to 90g/hr in one step.
FIXIncrease by 10–15g every two to three weeks. The gut adapts at training pace, not overnight.
MISTAKEUsing glucose-only products for high intake.
FIXAbove 60g/hr, fructose is essential to access the GLUT5 transporter. Use a 2:1 glucose-fructose product for any target above that threshold.
MISTAKESaving the new intake level for race day.
FIXDebut every intake level on training rides, multiple times, before bringing it to a race. GI distress at kilometre 80 of a sportive is not the place to discover your new limit.

FAQ

FREQUENTLY ASKED QUESTIONS

How long does it take to train your gut for cycling?

Four to six weeks of consistent, progressive practice on long rides produces measurable adaptation. Building from 60g/hr to 90g/hr typically takes 8–12 weeks when done properly — two to three weeks at each step.

Why do I get stomach problems with energy gels?

Most commonly: you are taking too much too fast, using a glucose-only product at too high an intake, or dehydrating while fuelling. Try slowing your intake, switching to a glucose-fructose product, and drinking 500–750ml of water per hour alongside your carbs.

Can I train my gut with real food instead of gels?

Yes. Bananas, rice cakes, dates, and homemade rice balls all work and are often better tolerated at low-to-moderate intake levels. They are harder to use at very high intake (90g/hr+) because of the volume required, but are excellent tools for building gut tolerance progressively.

What is the best ratio of glucose to fructose for cycling?

2:1 glucose to fructose is the most studied ratio and maximises the use of two separate intestinal transporters. Some products use 1:0.8 (close to 1:1) with good results. Avoid products that are purely glucose or purely fructose for intake above 60g/hr.

Should I drink water with my gels on the bike?

Yes — plain water, not more carbohydrate drink, with concentrated gels. The osmolality of concentrated carbohydrate draws water into your gut to dilute it, which can cause bloating if you are not adequately hydrated. Roughly 500–750ml of water per hour is the range to aim for.

RELATED EPISODES

HEAR THE CONVERSATIONS

Why Pros' 120g Carb Rule Fails Amateurs | Roadman Cycling

Under vs Optimal vs Overfueling on the Bike | Roadman Cycling Podcast

Ben Healy's 140g/hr Fueling Strategy | Roadman Cycling