Contribution of gastroenteropancreatic appetite hormones to protein-induced satiety1–3

Background: Effects of protein intake on appetite-regulating hor-mones and their dynamics are unclear. Objectives: We investigated the satiating effects of meals with varying protein contents and whether there was an effect of dose on appetite-regulating hormones and appetite ratings. Design: Twenty-five men [mean 6 SD age: 30.0 6 8.7 y; body mass index (BMI; in kg/m2): 25.9 6 4.7] participated in the 3-way, randomized, double-blind crossover study. Test meals were iso-caloric with 30 % of energy from fat and protein content adjusted at the expense of carbohydrate. Test meals were normal protein (NP; 14 % of energy from protein), medium-high protein (MHP; 25 % of energy from protein), and high protein (HP, 50 % of energy from protein). Appetite ratings and blood samples were assessed every 0.5 h for 4 h. An ad libitum lunch was served 4 h after the meal. Results: Protein increased dose-dependently glucagon-like peptide-1 (GLP-1), peptide YY (PYY) 3–36, and glucagon; MHP produced 10%, 7%, and 47 % greater responses, respectively; and HP produced 20%, 14%, and 116 % greater responses, respectively, than did NP (P, 0.03). Compared with NP, HP increased insulin and cholecystokinin and decreased ghrelin and glucose-dependent insulinotropic polypeptide (P, 0.05). Satiety and fullness dose-dependently increased by 7 % and 6 % for MHP and 16 % and 19% for HP compared with NP (P, 0.001). Hunger and prospective consumption dose-dependently decreased by 15 % and 13 % for MHP and by 25 % and 26 % for HP compared with NP (P, 0.0003). There was a combined effect of GLP-1 and PYY 3–36 (P = 0.03) next to the additive effect of GLP-1 (P = 0.006) on the composite appetite score. No difference was shown in ad libitum energy intake. Conclusion: Protein dose-dependently increased satiety and GLP-1, PYY 3–36, and glucagon, which may, at least in part, be responsible for the satiety-stimulating effect of protein. This trial was registered at clinicaltrials.gov as NCT01561235. Am J Clin Nutr doi: 10.3945/ajcn.112.047563