The ways protein creates lasting fullness.
What the evidence says
- Greater perceived fullness, elevated satiety hormones after higher-protein meals — and the same review finds this does not carry through to eating less at the next meal: across the 24 acute feeding trials it summarises, 11 (55%) showed increased postprandial fullness but only 3 (18%) observed any reduction in food intake at the next eating occasion[1]
- High-protein meals produce more sustained CCK stimulation and ghrelin suppression than other macronutrient compositions, potentially mediating protein’s superior satiating effect — measured in 16 lean and 16 obese men, no women[2]
- Protein-induced satiety may be mainly due to oxidation of amino acids fed in excess, especially with “incomplete” proteins[3]
- The body has no flexible storage capacity for protein — excess amino acids must be actively oxidized or eliminated, which increases thermogenesis[4]
- Protein TEF: 20-30% of calories consumed[5]
- Carbohydrate TEF: 5-10%[5]
- Fat TEF: 0-3%[5]
- Protein-induced thermogenesis has important effect on satiety[5]
- “Complete” proteins (all essential amino acids) produce larger increases in energy expenditure than lower-quality proteins[3]
- It ”has been suggested” that increased protein turnover accounts for most (68%) of the acute thermogenic effect of protein feeding (corrected 2026-09-10: the bullet stated the suggestion as a finding; `cps04` made the same correction today)[4]
- Net metabolizable energy of protein is 13 kJ/g (vs 17 kJ/g Atwater factor) due to thermic effect — lower than carbohydrate or fat[4]
- ”Theoretically”, the ATP required for the initial steps of metabolism and storage is why DIT differs by nutrient (corrected 2026-09-10 from ”Large ATP requirement for protein metabolism explains high thermic effect”: Theoretically restored; `cps05` made the same correction today)[5]
- Protein-induced energy expenditure driven by protein and urea synthesis and by gluconeogenesis[3]
- High-protein meals may increase thermogenesis via up-regulation of uncoupling proteins (UCP-2 in liver and UCP-1 in brown adipose tissue, both ”In animal models”) (species restored 2026-09-10, following `cps04`)[4]
- Hierarchy in macronutrient oxidation: alcohol > protein > carbohydrate > fat[5]
- Animal (pork) protein produces 2% higher energy expenditure than plant-based (soy) protein[4]
- Whey protein may increase satiety more than casein: faster gastric emptying and greater stimulation of CCK and GLP-1[4]
- Caseinomacropeptide (15-20% of whey products) stimulates CCK production; its effect on satiety has been found ”in some (34), but not all (35), studies” (corrected 2026-09-10 from ”and increases satiety”, following `cps04`)[4]