Nutrient-detecting gut neurons signal to the brain to drive eating behavior, even when food is delivered directly to the gut.

“Specific circuits in the gut sense sugar, independent of sweet taste.”

“there are neurons in the gut that sense dietary fat & trigger fat craving (not tastes).”

“Now the sugars are a little bit cryptic because when I say sugars or I say amino acids or I say fatty acids, this has nothing to do with taste. In fact, beautiful experiments have been done by the Bourhees lab and by other labs showing that even if you numb the mouth, even if you gavage, which is a really just a it's a fancy word for basically tube feeding, you put a tube down in the gut, you just deliver the food to the gut. So you get no opportunity to taste it. Sounds pretty awful. If you force feed by gavage or you numb the mouth, these neurons don't care about the mouth. They only care about the nutrients coming from these foods and then they signal to the brain, hey, do that thing. Do that thing where you lift that object we call a fork or a spoon. Do that thing where you drink the milkshake. Do that thing where you move your mouth like this, not talking, but do that thing where you swallow.”