Yes, even those with a sensitive stomach should still consume quickly absorbing (aka easily digested) carbohydrates during runs longer than 60 to 90 minutes. Finding the right option often takes some trial and error, which is why you should test it out during training runs. Research also shows that the gut is highly adaptable, meaning you can train it to accept fuel on the run. So, even if something doesn’t work for you the first time, you may be able to train your gut slowly to accept it.  Choose options with a mixture of carbohydrate sources and test out different sources, flavors, and forms. The good news is that there are a number of different options and even if one gel doesn’t work for you, another brand might—or a different product like a chew, dates, or a bar.  Those with a sensitive stomach may want to avoid products with fat and fiber as they can slow digestion too much during physical activity. Caffeine can send some people running to the bathroom, too, so caffeine-free options may be a better choice.