Your gut is trainable — glucose alone saturates at ~60g/hour, so dual-source carbs plus adaptation are what unlock 90g.
Build over 4–6 weeks: 30–40g/hour, then 60g/hour, then 80–90g/hour on two or three long sessions.
You can carry 90g of carbohydrate an hour in your pocket. Whether your stomach will actually accept it is a different question — and the answer depends on training. The gut is an adaptable, trainable organ. Ask it to handle a high carb load cold on race day and it may well rebel. Train it patiently over a few weeks and it learns to absorb more, faster, with less fuss. Here's how to do it.
Why 90g an hour needs a trained gut
High carb intake only works if your body can actually absorb what you swallow. Glucose is absorbed via one transporter that saturates at around 60g an hour. Push past that with glucose alone and the excess sits in your gut, drawing in water and causing the bloating, cramps and nausea runners dread.
The unlock is dual-source carbohydrate — glucose plus fructose. Fructose uses a separate transporter, so a blend can be absorbed at up to 90g an hour. But even with the right fuel, those transporters respond to training. The more regularly you fuel at high rates, the more of them your gut expresses — and the more comfortably it copes.
A step-by-step gut training plan
Treat gut training like any other adaptation: progressive, consistent, and specific to race day. Over four to six weeks:
Weeks 1–2: Establish the habit. On long sessions, fuel at 30–40g/hour using dual-source carbs. Get used to eating on the move at a set schedule rather than by feel.
Weeks 3–4: Build the load. Increase to 60g/hour on your key long runs or rides. Notice what your stomach tolerates and keep hydration steady alongside.
Weeks 5–6: Reach race pace and race load. Push to 80–90g/hour on at least two or three long sessions at goal effort. This rehearses both the amount and the intensity you'll face on the day.
Always practise at the effort level you'll race at. A gut that copes at an easy jog can still complain at threshold, because blood is diverted away from digestion when you push hard.
Make the maths easy with Rosso
Gut training is far simpler when your fuel is consistent and easy to count. Rosso, our new 30g dual-source energy gel, is built for exactly this. Each gel delivers 30g of natural glucose and fructose from real fruit juice plus 150mg of sodium, so hitting your target is a matter of counting gels: two an hour is 60g, three an hour is 90g.
That consistency matters when you're building tolerance — you want to know precisely how much you're taking on at each stage. And because Rosso uses real fruit rather than a high concentration of synthetic sugars, it's designed to sit lighter on the stomach through the process. It's Informed Sport certified, vegan and free from artificial sweeteners and colours — real fuel your gut can learn to use.
Tips to make gut training work
Pair carbs with fluid. Carbohydrate needs water to be absorbed. Sip consistently alongside your gels.
Don't skip electrolytes. Sodium supports fluid absorption and helps prevent the nausea that can derail high-carb fuelling.
Be consistent. Occasional high-carb sessions won't drive adaptation. Regular exposure will.
Keep a simple log. Note what you took, when, and how your stomach felt. Patterns emerge quickly.
Progress gradually. If a jump in intake causes trouble, hold at the previous level for another session before building again.
Be patient — it works
Gut training isn't glamorous, but it's one of the highest-return things an endurance athlete can do. Master it and you unlock the top of the carbs-per-hour range that separates a strong finish from a fade. Start early, build steadily, and by race day your stomach will be as race-ready as your legs.
Can you really train your gut to absorb more carbs?
Yes. The gut adapts to regular high-carb fuelling by increasing the transporters that absorb carbohydrate. With consistent training over 4–6 weeks, most athletes can build comfortably toward 90g per hour.
How long does it take to train your gut?
Most athletes see meaningful adaptation within four to six weeks of consistent practice, building intake gradually from around 30g/hour up to 80–90g/hour.
Why can't I just eat 90g of glucose per hour?
Glucose is absorbed by a single transporter that saturates around 60g per hour. Beyond that, the excess draws water into the gut and causes bloating and nausea. Adding fructose — a dual-source blend — uses a second pathway so you can absorb up to 90g/hour.
How does Rosso help with gut training?
Rosso delivers a consistent 30g of dual-source carbs per gel, so it's easy to count your intake precisely as you build tolerance — two gels for 60g/hour, three for 90g/hour. Its real-fruit recipe is designed to sit light on the stomach.
Should I train my gut at race pace?
Yes. Digestion is affected by intensity, so practise your high-carb fuelling at the effort level you'll race at, not just on easy sessions.
