As sibling comments stated, that's why you see recommendations to eat during longer exercise sessions. A common recommendation I've seen is that for an hour or

As sibling comments stated, that's why you see recommendations to eat during longer exercise sessions. A common recommendation I've seen is that for an hour or less of activity your internal stores should suffice, but for more than an hour 30-90 grams of (probably easy-to-digest) carbs per hour of exercise is recommended.