Research · Nutrition ·
120g of carbs per hour, is more always better?
Very high carbohydrate intakes, up to 120g per hour, have become popular in endurance sport. This study tested whether going from 90g to 120g per hour actually changes what happens in the body.
What they did
Eleven highly trained male cyclists each did two 3-hour rides at a steady, moderate intensity, after an overnight fast. In one ride they took 90g of carbohydrate per hour, and in the other 120g per hour, both as a mix of fructose and maltodextrin (a carbohydrate made of chains of glucose).
The researchers measured how much of the carbohydrate they were eating was being used for energy (exogenous carbohydrate), and how much came from the body's own stores (endogenous carbohydrate).
What they found
- At 120g per hour, the body used more of the eaten carbohydrate in the final hour: 1.51g per minute, compared with 1.29g per minute at 90g per hour.
- The body's own stores were used at the same rate in both conditions. The extra carbohydrate didn't spare any more of them.
- The authors concluded that 90g per hour, in a 1:2 fructose to maltodextrin ratio, remains the recommended approach for exercise of this length.
What it means for ultra runners
More carbohydrate was absorbed and used, but there was no extra saving of your own glycogen in 3 hours. For ultra runners, 90g per hour is a well-supported target if your gut can handle it. Going higher may not bring extra benefit, and can be harder for the gut to tolerate.
Whatever you aim for, practise it in training first. Your gut can be trained to tolerate more (see our post on gut training).
Limitations
- The participants were cyclists, not runners. Running jostles the gut more, so tolerance may be lower.
- The exercise lasted 3 hours, much shorter than most ultras.
- It measured how carbohydrate was used, not race performance.
- Only 11 men took part.
This is a summary for information only, not medical or dietary advice. Read the original study for full details.