You take a bite of food and start chewing.
Chewing breaks your food (i.e., the mishmash
of macronutrients, water, fiber, and
micronutrients) into smaller pieces, and an
enzyme in your saliva starts to break the
carbohydrates down into simple sugars.
When you swallow that food, it moves
into your stomach. Essentially nothing
happens to carbohydrate and fat in the
stomach, but protein gets some attention—the
acidic environment of the stomach, plus some
digestive enzymes, start to break the protein
down into smaller pieces.
Your stomach also acts as a sensor for
satiety, talking to your brain through both the
nervous system and hormones. The stomach’s
message that you’ve eaten also tells your
brain to allow more energy to be used.
Your stomach then releases a controlled
flow of this mixture of food and digestive
enzymes into your small intestine, where bile