Why protein tops the satiety ranking
The satiety index ranks how strongly a fixed amount of food suppresses hunger over the following hours. Protein consistently scores highest, with fiber close behind, then fat, then refined or rapidly digested carbohydrate at the bottom. The original satiety index work by Holt and colleagues (1995) tested isocaloric portions and found large spreads, with boiled potatoes and lean protein rating far above white bread and pastries.
Several mechanisms plausibly contribute. Protein has a high thermic effect and slows gastric emptying, and it influences satiety hormones such as GLP-1, PYY, and cholecystokinin while blunting ghrelin. Fiber adds bulk and viscosity that slow digestion. These are mechanistic descriptions of average tendencies, not guarantees for any individual meal.
Where refined carbohydrate lands and why
Refined carbohydrate digests quickly, produces a sharp glucose rise and fall, and tends to leave hunger returning sooner, which is why it sits low on the index. Whole-food carbohydrate sources with intact fiber, such as legumes and oats, behave very differently from refined flour and sugar, so carbohydrate as a category spans a wide range.
Satiety scores measure short-term fullness from single test meals and do not by themselves prove long-term weight outcomes, which depend on total energy intake, food variety, and adherence. This is general educational information, not dietary prescription; anyone managing a medical condition should consult a qualified professional.