Here’s the way it should happen.
You put the food in your mouth. Your brain then registers the taste and texture of what you’re eating. The fats and sugars you’re eating promote eating more. Then you swallow your food and it enters the gastrointestinal tract. As your stomach distends, the volume of the food you’ve ingested is relayed to your brain. Gastric signals of ‘growing full’ begin to conflict with the ‘eat more’ signals coming from the food in your mouth. The chemicals and nutrients of the food in the gastrointestinal tract lead to the release of peptides and neurotransmitters that send ‘I’m satisfied with what I ate’ signals to your brain. These signals inhibit your eating to the point where you stop eating. You feel fed to satisfaction, and then you can go from the end of this meal to the start of your next meal without feeling the need to eat more in between.