title: The satiating effect of dietary protein is unrelated to postprandial ghrelin secretion.
abstract: BACKGROUND
  Increasing dietary protein relative to carbohydrate and fat enhances weight loss, at least in part by increasing satiety. The mechanism for this is unclear.
  
  
  OBJECTIVE
  The objective of this study was to compare the effects of isocaloric test meals with differing protein to fat ratios on fasting and postprandial ghrelin, insulin, glucose, appetite, and energy expenditure before and after weight loss on the respective dietary patterns.
  
  
  METHODS
  The study design was a randomized parallel design of 12 wk of weight loss (6 MJ/d) and 4 wk of weight maintenance (7.3 MJ/d) with meals administered at wk 0 and 16.
  
  
  METHODS
  The study was performed at an out-patient research clinic.
  
  
  METHODS
  Fifty-seven overweight (body mass index, 33.8 +/- 3.5 kg/m2) hyperinsulinemic men (n = 25) and women (n = 32) were studied.
  
  
  METHODS
  High-protein/low-fat (34% protein/29% fat) or standard protein/high-fat (18% protein/45% fat) diets/meals were given.
  
  
  METHODS
  The main outcome measures were weight loss and fasting and postprandial ghrelin, insulin, glucose, appetite, and energy expenditure before and after weight loss.
  
  
  RESULTS
  Weight loss (9.2 +/- 0.7 kg) and improvements in fasting and postprandial insulin and glucose occurred independently of diet composition. At wk 0 and 16, subjects wanted less to eat after the high-protein/low-fat than the standard protein/high-fat meal (P = 0.02). Fasting ghrelin increased (157.5 +/- 3.4 pg/ml or 46.6 +/- 1.0 pmol/liter; P < 0.001), and the postprandial ghrelin response improved with weight loss (P = 0.043) independently of diet composition. Postprandial hunger decreased with weight loss (P = 0.018) and was predicted by changes in fasting and postprandial ghrelin (r2 = 0.246; P = 0.004). Lean mass was the best predictor of fasting (r2 = 0.182; P = 0.003) and postprandial ghrelin (r2 = 0.096; P = 0.039) levels.
  
  
  CONCLUSIONS
  Exchanging protein for fat produced similar weight loss and improvements in metabolic parameters and ghrelin homeostasis. The reduced appetite observed with increased dietary protein appears not to be mediated by ghrelin homeostasis.
authors: Commonwealth Scientific and Industrial Research Organization (Australia), Health Science and Nutrition, University of Adelaide, Australia. lisa.moran@csiro.au
authors: Lisa J
authors: LJ
authors: Moran
authors: Natalie D
authors: ND
authors: Luscombe-Marsh
authors: Manny
authors: M
authors: Noakes
authors: Gary A
authors: GA
authors: Wittert
authors: Jennifer B
authors: JB
authors: Keogh
authors: Peter M
authors: PM
authors: Clifton
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition; D001835:Body Weight; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000627:therapeutic use; D004734:Energy Metabolism; D005215:Fasting / Q000097:blood; D005260:Female; D054439:Ghrelin; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood / Q000150:complications; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000178:diet therapy*; D010147:Pain Measurement; D036361:Peptide Hormones / Q000097:blood / Q000378:metabolism*; D019518:Postprandial Period / Q000502:physiology*; D012044:Regression Analysis; D012527:Satiation / Q000187:drug effects*
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D054439:Ghrelin; D007328:Insulin; D036361:Peptide Hormones