AI quick summary
- Carb intake by duration: rides under 2 hours need ~30 g/hr, 2–3 hours need 60 g/hr, 4+ hours need 90 g/hr, and ultra-endurance can push to 120 g/hr with the 2:1 glucose:fructose ratio
- The 2:1 ratio matters for high intake (90+ g/hr): glucose uses one gut transporter, fructose uses another. Combining them lets you absorb more total carbohydrate without gastric distress
- Drink to thirst, not to a schedule — modern sports science says thirst-guided hydration beats the old 'drink before you're thirsty' advice for most riders
- Practice your fueling: race-day nutrition should be tested on training rides. Your gut adapts to high carb intake — don't try 90 g/hr for the first time on event day
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Carbs per hour by duration
Target carbohydrate intake by ride duration. Start conservatively and build up — your gut adapts.
| Ride duration | Target carbs | What's happening | Example |
|---|---|---|---|
| <2 hours | 30 g/hr | Tapping glycogen stores; light fueling | One gel or half a bar + a bottle with carb drink |
| 2–3 hours | 60 g/hr | Depleting glycogen; need steady carb input | Two gels or one gel + one bar + carb drink |
| 3–4 hours | 90 g/hr | Max single-source glucose absorption | Two gels + carb drink + on-bike snacks (banana, rice cakes) |
| 4+ hours / ultra | 90–120 g/hr (2:1 ratio) | Requires dual-source fueling | Carb drink (maltodextrin+fructose) + gels + real food |
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The 2:1 glucose:fructose ratio
Your gut has two separate transporters for carbohydrate: one for glucose (and glucose polymers like maltodextrin) and one for fructose. Each can absorb ~60 g/hr. By combining glucose and fructose in a 2:1 ratio, you can absorb ~90 g/hr total — more than either alone. Push to 1:1 and you can hit ~120 g/hr, but many riders find that ratio causes gastric distress; 2:1 is the sweet spot for most.
Modern carb drinks (Maurten, SiS Beta, Skratch Superfuel) use this 2:1 ratio. Homemade option: 60 g maltodextrin + 30 g fructose per bottle. This is cheaper than branded products and equally effective if you mix it correctly. Add a pinch of sodium (500–750 mg per bottle) to aid absorption.
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Real food vs gels vs carb drink
Carb drink is the foundation: it combines fueling and hydration in one, and you're drinking throughout the ride anyway. Make every bottle count — have a carb drink (not just water) on any ride over 90 minutes. For a 3-hour ride, two bottles with 60 g carbs each = 120 g total = 40 g/hr — almost hitting the 60 g target without any gels or food.
Gels are the supplemental fuel: one gel (~25 g carbs) every 45–60 minutes on top of the carb drink for higher intensity or longer rides. Real food (banana, rice cakes, flapjack, date bars, a sandwich on a stop) is for long, steady rides where you can digest slowly. The mix: carb drink as the base, gels for intensity, real food for comfort and variety on long days.
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Practice and gut adaptation
Your gut CAN adapt to higher carb intake, but you need to train it. Start with 60 g/hr on training rides, progressively increase to 80–90 g/hr over several weeks, and watch for gastric distress (nausea, bloating, cramping). These are signs you've exceeded your current absorption rate — dial back and build gradually.
The golden rule: never race an untested fueling plan. The gel you've never tried, the carb drink at race concentration, the pre-race breakfast you've never eaten before a ride — these are how bonks and porta-potty stops happen. Every variable should be tested on a training ride first.
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