title: Effects of acute and chronic protein intake on metabolism, appetite, and ghrelin during weight loss.
abstract: OBJECTIVE
  This study evaluated the effects of acute and chronic consumption of higher dietary protein on energy expenditure, macronutrient use, appetite, and appetite-regulating hormones during weight loss in women.
  
  
  METHODS
  Thirty-eight women chronically consuming a 750 kcal/d energy-deficit diet with a protein content of 30% (higher protein-chronic diet, HP-CD, n = 21) or 18% (normal protein-chronic diet, NP-CD, n = 17) for 9 weeks were tested. On separate days, metabolic, appetite, and hormonal responses were measured over 4 hours when the women consumed a higher protein-acute meal (HP-AM) (30% of energy as protein) or a normal protein-acute meal (NP-AM) (18% of energy as protein).
  
  
  RESULTS
  With chronic diet groups combined, HP-AM led to lower respiratory exchange ratio (0.829 +/- 0.005 vs. 0.843 +/- 0.008; p < 0.05), lower carbohydrate oxidation (p < 0.05), and higher fat oxidation (p < 0.05) compared with NP-AM. HP-AM also led to reduced self-reported postprandial hunger (p < 0.001) and desire to eat (p < 0.001) and lower postprandial ghrelin (252 +/- 16 vs. 274 +/- 18 ng/mL x 240 minutes, p < 0.05) compared with NP-AM. No differences in postprandial energy expenditure (PPEE) occurred between meals. When combining acute meals, respiratory exchange ratio was lower (p < 0.05) and protein oxidation (p < 0.001) was higher in the HP-CD vs. NP-CD. An acute meal-by-chronic diet interaction was observed with PPEE such that HP-AM led to greater PPEE in the HP-CD vs. NP-CD (28.7 +/- 2.7 vs. 19.9 +/- 2.7 kcal/min for 195 minutes; p < 0.05).
  
  
  CONCLUSIONS
  During weight loss, thermogenesis and protein use appear to be influenced by chronic protein intake, while appetite and ghrelin are more responsive to acute protein intake.
authors.affiliation: Department of Foods and Nutrition, Ingestive Behavior Research Center, Purdue University, 700 West State Street, West Lafayette, IN 47907, USA. hleidy@purdue.edu
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Leidy
authors.forename: Richard D
authors.initials: RD
authors.lastname: Mattes
authors.forename: Wayne W
authors.initials: WW
authors.lastname: Campbell
mesh_terms: D001066:Appetite / Q000502:physiology*; D001833:Body Temperature Regulation / Q000187:drug effects; D004038:Diet, Reducing; D004044:Dietary Proteins / Q000494:pharmacology*; D002149:Energy Intake; D004734:Energy Metabolism / Q000187:drug effects; D005260:Female; D054439:Ghrelin; D006801:Humans; D009765:Obesity / Q000178:diet therapy*; D050177:Overweight / Q000502:physiology; D010101:Oxygen Consumption / Q000187:drug effects; D036361:Peptide Hormones / Q000097:blood*; D019518:Postprandial Period; D015431:Weight Loss / Q000502:physiology*
chemical_list: D004044:Dietary Proteins; D054439:Ghrelin; D036361:Peptide Hormones