How Much Carb You Can Eat vs Actually Use

From Sweat Science

The ingestion rate in some of the studies was as high as 2.4 g/min, which works out to 144 g/hr — pretty much the same as what Josh was doing, and far higher than the 90-100 g/hr thought to be the max. But how much of this intake were they actually burning? The exogenous carb oxidation rate tops out at 1.70 g/min (102 g/hr), in line with expectations. And if you’re just using plain old glucose while stuffing in all those carbs, fully half of them go to waste. So the moral: if you can pack in 150g /hr of carbs while doing an Ironman, you’re blessed with a very strong stomach — but it doesn’t mean you’re using all of it.