Question:
Why is it that we can eat more or less depending on our level of relaxation?

I'm sure it has to do with the muscles being more or less relaxed, but I still think it's sort of interesting....    — Donna S. C. (posted on March 26, 2001)

March 26, 2001
OK, this is probably not a complete answer by any means, but here goes.... The autonomic nervous system, which is the stuff we can't consciously control (including digestion) has two parts: sympathetic ("fight-or-flight") and parasympathetic ("rest-and-digest"). The two sort of compete with each other for control. When the sympathetic system is stronger--when you're keyed up--there is less blood flow to the digestive system and secretions (stomach acid, bile salts, pancreatic enzymes) are decreased. When the parasympathetic system is winning--when you're relaxed--blood flow and secretions increase. So when you're tense, your body has other things on its mind, so to speak, than food; when you're calm, your body is ready to spend some time digesting. (I should admit right now I'm a first-year vet student--but don't hold that against me! I have studied digestion a little, and the basics are pretty consistent from mammal to mammal.)
   — Kristy S.