Learn · Fueling
How many carbs per hour on a gran fondo?
The short answer: on a ride of two to three hours, aim for about 60 grams of carbohydrate per hour. On longer rides, which is most gran fondos, aim for about 90 grams per hour from a mix of glucose and fructose. More than 90 is possible for trained riders with a trained gut, but there is little evidence yet that it makes you faster.
Why 60 and 90?
Your gut absorbs glucose through one transporter, SGLT1, and that transporter is saturated at around 60 grams per hour. Eat more glucose than that and it is not absorbed any faster; on a single sugar, your muscles burn at most about 1 gram of carbohydrate from food per minute 1.
Fructose is absorbed through a different transporter. Take glucose and fructose together, typically two parts glucose to one part fructose, and riders in lab studies burned about 1.26 grams per minute instead 1. That second door is what makes 90 grams an hour work.
Ride length matters, body weight does not
The guidelines scale with how long you ride, not with how much you weigh or how fit you are 1:
| Ride length | Carbs per hour | What kind |
|---|---|---|
| About 1 hour | Little or none; a mouth rinse can help | Anything |
| 2 to 3 hours | Up to about 60 g | A single sugar is enough |
| Longer | About 90 g | Glucose and fructose, about 2:1 |
What about 120 grams an hour?
You may have heard of riders taking 120 grams an hour. In one lab study, 11 highly trained male cyclists rode for three hours taking either 120 g/h, with nearly equal parts fructose and glucose, or 90 g/h at the usual 2:1 2. At 120 g/h they burned more of the carbohydrate they took in, and they reported no more stomach trouble. But it did not spare their own glycogen stores, and the study did not test whether they rode faster.
So 120 grams an hour can be absorbed by a trained rider with a trained gut. Whether it helps you is still an open question, and race day is not the place to find out.
Train your gut
The gut adapts. In one study, a high-carbohydrate diet for four weeks increased how much carbohydrate from drinks riders could burn during exercise 1. If you want to race at 90 grams an hour, practise it on your long training rides first, with the same products you will use on the day.
Putting it into a plan
Grams per hour only help if they turn into gels, bars and bottles at the right feed stations. The FondoLab fueling planner takes your target and your feed points and works out what to take on at each stop, and warns you when your target needs glucose and fructose together.
References
- Jeukendrup A (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine 44(Suppl 1):25–33. doi:10.1007/s40279-014-0148-z
- Podlogar T, Bokal Š, Cirnski S, Wallis GA (2022). Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h−1 versus 90 g h−1 at different ratios. European Journal of Applied Physiology 122(11):2393–2401. doi:10.1007/s00421-022-05019-w