How to Train Your Gut to Handle 90g of Carbs an Hour: A 6-Week Protocol

Every few years the guidance on carbohydrate intake during endurance sport creeps upwards. It used to be 30-60g an hour. Now the sports science consensus for events longer than about two and a half hours is 90g an hour, and some elite athletes go well beyond that. The catch is that most of us turn up to our first attempt at 90g, feel sloshing and bloated by hour two, and conclude that it simply isn't for us.

It usually is for us. It just needs training. Your gut adapts to carbohydrate in much the same way your legs adapt to threshold work: gradually, specifically, and only if you keep asking. This is a practical gut training 90g carbs protocol you can run over six weeks, with real numbers, so you arrive at your key event having done the rehearsal rather than the experiment.

Why 90g an Hour Is Even Possible

Your small intestine absorbs glucose through a transporter called SGLT1, and that pathway saturates at roughly 60g an hour. Push more glucose down it and the excess sits in your gut, pulling water in and causing the cramping and urgency every endurance athlete dreads. Fructose uses a different transporter, GLUT5. Combine the two and total absorption can reach 90g an hour or more.

This is why the mix matters. A glucose-to-fructose ratio of around 2:1, or closer to 1:0.8 at higher intakes, lets both pathways work in parallel. If you are fuelling with a single sugar source, 90g an hour is not a training problem, it is a plumbing problem. Sort the ratio first, then train the gut.

What Gut Training Actually Changes

Research on athletes who repeatedly consume carbohydrate during training shows several adaptations. Transporter expression in the intestinal lining appears to increase, gastric emptying becomes quicker and more tolerant of volume, and the symptoms you notice, nausea, bloating and cramps, reduce noticeably. Studies where participants trained with high carbohydrate intakes for a couple of weeks reported fewer GI symptoms and better absorption than controls who stayed on their usual intake.

It is also partly psychological. Once you have eaten 80g an hour for a few sessions without incident, your brain stops treating the feeling of a full stomach as an emergency. That alone makes a surprising difference on race day.

The 6-Week Gut Training 90g Carbs Protocol

The rule is simple: two sessions a week carry the load, everything else stays normal. Pick sessions of at least 90 minutes, ideally your long ride or long run plus one steady endurance session. Your intensity should be at or below tempo. Do not attempt this in a threshold session, where blood is diverted from your gut and tolerance is lowest.

• Week 1: 60g an hour in both sessions. This is your baseline. If you already do this comfortably, great. If not, stay here until you can.
• Week 2: 70g an hour. Take small amounts every 10 to 15 minutes rather than big hits every 30.
• Week 3: 75g an hour. Note any symptoms in a training log, even minor ones. Patterns show up quickly.
• Week 4: 80g an hour. This is typically where the first rough patch appears. Drop back 5g if you need to and repeat the week.
• Week 5: 85g an hour. Practise with the exact products and drink mix you plan to race with.
• Week 6: 90g an hour in your longest session, at your planned race intensity for the first hour. Then taper.

If a week goes badly, repeat it rather than pushing on. The goal is not to rush the schedule. Most people need seven or eight weeks to finish the full progression, and that is perfectly fine.

Making 90g Practical

Ninety grams an hour sounds enormous until you break it down. If your chews or pastilles deliver around 6g of carbohydrate each, 90g is fifteen pieces an hour, or one every four minutes. That is manageable if you set a repeating timer and treat it as part of the ride rather than an interruption.

Spread your intake between solids, chews and a carbohydrate drink mix. Fluid is not just a carrier; drinking around 500-750ml an hour alongside your carbs helps keep gastric emptying going. Very concentrated drinks above roughly 10% carbohydrate can slow it down, so keep your bottle mixes sensible and take your chews with water.

Finally, avoid adding fibre, fat and protein-heavy foods in the hours around your sessions. They slow gastric emptying, which is helpful on a rest day and unhelpful when you are trying to absorb 90g of sugar.

Common Mistakes

The biggest one is jumping straight to the target. Going from 40g to 90g in a single session is the fastest way to make gut training feel like a failure. The second is training with different products to those you race with. Your gut learns what you feed it, including the specific sugar ratio and the volume of fluid. The third is ignoring heat. Warm conditions reduce gut blood flow and tolerance, so if your race will be hot, do some of your gut training in similar conditions.

Also resist the urge to compensate by eating less the night before. Arrive well fuelled, because a depleted athlete starting a session has less physiological reserve to tolerate anything.

What We Use at FTP Endurance Fuel

We built our pastilles around exactly this problem. They use a glucose and fructose blend at a 1:1 ratio, are small enough to take a piece every few minutes without breaking your rhythm, and the gummy texture means you are not wrestling with a sticky gel at 40km an hour. For the tart cherry version, you also pick up anthocyanins, which are a handy bonus on those back-to-back training days.

If you are starting your gut training block, the Taster Pack is a low-risk way to confirm you get on with the flavours. Once you have settled on your favourite, the Mixed Fruit Pastilles 1kg bag gives you enough to get through the whole six weeks without running out halfway through your Week 4 session.

Race Day

By the time you reach your event, 90g an hour should feel dull. Set your timer, take small frequent doses, and keep it identical to what you rehearsed. Anything new on race day, a different product, a different flavour, an extra gel because you feel good, is a variable you haven't tested.

Gut training is one of the cheapest performance gains available to an endurance athlete. Six weeks, two sessions a week, and a plan. Start with the FTP bundles and get your first session in this weekend.