NARRATOR: Thanksgiving dinner! Turkey, stuffing, mashed potatoes, more turkey, cranberry sauce, gravy, even more turkey ... uuugh. Still have room for pie? For now, unbutton your eating pants, flop on the couch, and let’s learn why you feel so full after a big meal.
Part of the reason is physical. Your stomach can stretch to the volume of about 1 litre. That’s about the size of a burrito. When you eat a big meal, you fill your stomach to its limits, squeezing against your other organs and making your abdomen feel, well, full. Your stomach and intestines also fill with gases that you eat, adding to that swollen sensation. Each time you swallow, a bit of air goes along for the ride. Even more if you’re drinking soda or beer. Inside your stomach, the gas that makes your drink fizzy fills more space than the liquid it came in.
Fortunately, your body has a good way of getting rid of the excess gas built up in the stomach (burp!). For some people, another uncomfortable result of a big meal is heartburn. The stomach produces hydrochloric acid to break down food. More food to break down means more acid, which can irritate the lining of the stomach and creep into the esophagus, leading to that burning feeling. Antacid tablets use bases (remember, the opposite of an acid is a base) like calcium carbonate to neutralise the acid. That reaction produces more carbon dioxide which can increase that full feeling, at least until your next burp.
The other part of feeling full is mental. When you’ve had enough to eat, the body’s messenger molecules, hormones, let the brain know it’s time to stop. Bro? Bro?! It’s time to stop. When you eat a high-calorie meal, cells in your intestines secrete a hormone called peptide-tyrosine-tyrosine or PYY. Not PYT. That’s a Michael Jackson song. When PYY reaches the brain, it binds with receptors that give you the feeling that you’re full. Maybe even a little queasy. Some hormones react more strongly to meals heavy in fats, carbohydrates or proteins, but they all serve the same purpose—to get you to put down that fork.
So the next time your mum asks you if you want seconds, maybe take a minute to listen to what your body’s trying to tell you. Or just keep stuffing your face, I don’t care really. But don’t be surprised if you’re not feeling so good after.