Reader Stacey asks if it’s really true that it’s the sense of taste that cues the brain to tell us if we’ve had enough to eat. Staci, I was more confident of my answer before I found out that there was a full-on satiation researcher following this conversation (see the comments on the below post). So expect to see a lot more qualifiers and far fewer declarative sentences moving ahead. But yes, that’s at least partly true.
As I understand it, it’s our umami sensors that bear much of that burden. Umami is stimulated primarily by glutamic acid, a so-called proteinogenic amino acid, which is to say, an amino acid that’s used as a building block of protein molecules. Thus it’s found in all sorts of protein-rich foods like meat, milk and cheese, which by no coincidence whatsoever are the types of foods that most people associate with a sense of satiety or “fullness.”
Stimulate umami receptors and feelings of satiety increase. This is what the food additive MSG (monosodium glutamate, the sodium salt of glutamic acid) does: it gives people who eat it that happy satisfied feeling. Or so I, er…understand.