Adrenal hormones have an affect on the action of
insulin, which is released faster with high carbohydrate consumption. For instance, epinephrine can "turn off" insulin production, and of course all of our hormones, including the interplay between thyroid and adrenal hormones, work together to try and maintain balanced function of every organ, and they have a strong effect on gut function.
My son has trouble eating only carbs. It can cause stomach upset and tachycardia.