Originally Posted by chasm54

There is some evidence, I believe, that some easily-digestible formulations of carb-rich drinks deliver a slightly faster rate of absorption, but the difference isn't that significant in the context of the energy one is burning on the bike.

The point is not that eating more gives rise to adverse effects, though personally I dislike riding with too full a stomach. The issue is simply that if you eat more than 250kcal of carbs per hour while riding, you'll be digesting the surplus after you've finished the ride, so it won't help you.