How Much Carbohydrate Do Athletes Need Per Hour?

Carbohydrate is the primary fuel source for high-intensity endurance exercise. But ask most athletes how many grams per hour they should be taking in, and you'll get a vague answer — or none at all.

This is the most important question in race nutrition. Here's what the science actually says.

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Why Amount Matters More Than Source

Sports nutrition marketing has spent decades focusing on what kind of carbohydrate is in a product — hydrogel technology, cluster dextrin, dual-source blends — rather than helping athletes understand how much they need. The source matters, but it's secondary. Get the amount wrong and no formulation will save your race.

Think of it like Maslow's hierarchy of needs: the foundational question is quantity. Type and source sit further up the pyramid, only relevant once the basics are dialled in.

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Why You Need Carbohydrates During Exercise

Your glycogen stores – the carbohydrate stored in your muscles and liver – are finite. Roughly 90–120 minutes of hard effort is enough to deplete them to a level that significantly compromises performance. Beyond that point, relying on fat as a primary fuel source doesn't support the output required to race hard.

Consuming carbohydrates during exercise provides what's known as exogenous fuel — energy from outside your body's stores, delivered in real time.

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How Much Carbohydrate Per Hour?

Note: these recommendations assume you start exercise with full glycogen stores and are working at genuine race intensity.

Less than 1 hour

In most cases, no carbohydrate intake is needed. Your glycogen stores will see you through. For very high-intensity efforts of 45–60 minutes, a small amount of carbohydrate or even a carb mouth rinse may marginally help performance.

1–2 hours

Aim for 30–60g of carbohydrate per hour. The harder the effort and the longer the duration within this bracket, the more benefit you'll get from pushing towards 60g.

2+ hours

Athletes working hard beyond the 2-hour mark can benefit from 60–90g per hour. At this level, using a mix of glucose and fructose (multiple transportable carbohydrates) becomes important — different sugars use different absorption pathways in the gut, allowing higher total uptake.

Ultra distance (6+ hours)

Beyond pure carbohydrate strategy, ultra-distance fuelling introduces additional considerations: fat and protein from real foods, taste fatigue from single-source fuels, and the practical reality of eating while moving for many hours. The per-hour carb model remains useful but is not the complete picture.

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Does Body Size Change Your Needs?

Less than you'd expect. Carbohydrate absorption is primarily limited by gut transport rate, which is similar across athletes regardless of body mass. A 55kg athlete and a 90kg athlete absorb carbohydrate at roughly the same rate per hour. As a result, the gram-per-hour recommendations apply broadly regardless of size.

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What 30, 60, and 90g Per Hour Looks Like

To hit 90g/hour, you're combining multiple sources. This is a real skill that takes gut training over several weeks — don't attempt it for the first time on race day.

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Training Your Gut

Most amateur athletes undereat during races. If the numbers above are higher than your current intake, that's good news — there's performance to be unlocked. Start by nudging your intake upward during one or two hard sessions per week, increasing gradually over 4–6 weeks until your gut adapts.

GI distress at high carbohydrate intakes is common initially but typically improves with consistent exposure.

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Key Takeaways

• Under 1 hour: No carbohydrate needed in most cases
• 1–2 hours: 30–60g per hour
• 2+ hours: 60–90g per hour, using mixed carbohydrate sources
• Body size is not a major factor in setting carb intake
• Most athletes undereat — there is likely performance available by increasing intake
• Gut training is required before racing at high carbohydrate volumes