Is there a science backed ceiling for

Nutrition Q&A [Moderated]
1

NOTE: Posted without finishing my Title. Please delete to hide my shame.

Hello Docs,

I have a 12 hour endurance event planned in July this year, so I have been investigating and experimenting with strategies for eating during the event. I have found in a number of places people repeating the following: “During exercise, your body can only digest 1 gram of carbohydrate per minute so you should plan to eat about 240 calories per hour. (60g/h * 4 calories = 240 cal/h)” This statement is usually follow by saying you’ll have GI issues if you eat more. I expect that in practice what people can “digest” will vary because of factors like: the individual, temperature, exercise intensity, food type, exercise modality, etc.

Is there any scientific basis for that 1g/m number?

Thanks

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The best evidence I’ve seen on this suggests an upper limit ~ 1.2 grams of glycogen re-synthesis per kilogram bodyweight per hour during this type of activity, but this doesn’t really tells us much about how much you should eat during activity.

Based on existing evidence, it seems like this is mostly personal preference with respect to GI symptoms, the event, the environment, and so on. In general, we recommend folks doing prolonged endurance training performance (> 90 minutes) consume ~ 0.7 grams of carbohydrates per kilogram body weight per hour up to a maximal dose of 60-90 grams per hour. A 6-8% carbohydrate solution, e.g. 6-8 grams of carbohydrates per 100 ml of fluid may be beneficial.