What it means
Peptide YY is made by L-cells in the lower small intestine and colon, the same cells that release GLP-1. Levels rise after eating, especially after protein and fat, and fall during fasting.
The main circulating form, PYY 3-36, acts on receptors in the brain that dampen appetite. PYY levels rise sharply after some bariatric surgeries, which is one proposed reason those operations reduce hunger so much.
Drug makers have tried to turn PYY into a medicine, often in combination with GLP-1. Early versions caused nausea at doses high enough to matter, and no PYY-based drug is FDA-approved.
Supplements or diets marketed as "boosting PYY" have not been shown to produce the weight effects seen with prescription medicines. Eating enough protein and fiber is a reasonable habit for fullness, but it is not a substitute for treatment.
Why it matters
PYY helps explain why protein-rich meals and some surgeries affect fullness, and it remains a target for future drugs.
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