title: Whole-body protein turnover in obese subjects during two very low energy diets of differing amino acid composition.
abstract: OBJECTIVE
  To determine whether the kinetics of protein metabolism would differ with the prolonged use of a casein-soy 96 g protein, 1.7MJ/d very low energy diet (VLED) from those of a tryptophan- and methionine-supplemented hydrolyzed collagen VLED, in obesity.
  
  
  METHODS
  Clinical intervention study of 1 week isoenergetic diet followed by 6 weeks VLED.
  
  
  METHODS
  6 (1M,5F) healthy obese subjects (age: 38 +/- 4 y, BMI: 33 +/- 1 kg/m2, weight: 97 +/- 7 kg).
  
  
  METHODS
  Whole-body nitrogen (N) flux rate (Q) from 15N abundance in urinary urea using the oral 15N-glycine method and rates of protein synthesis (S) and breakdown (B) calculated from Q; N balance; resting metabolic rate; metabolic and hormonal responses.
  
  
  RESULTS
  Q (per kg LBM) was maintained with both collagen and casein-soy VLED. S and B decreased (P < 0.05) at week 4 of both VLEDs with resulting decreases in net protein synthesis. At week 6, S decreased with both VLEDs, but B decreased only with casein-soy, at which time N balance was at equilibrium with casein-soy but returned to negative with collagen. Initial resting metabolic rate correlated with baseline Q and S. It decreased by 16% with the VLEDs; 25% of the decrease may derive from the decline in S.
  
  
  CONCLUSIONS
  A 6 week casein-soy VLED with 46% of amino acids as essential does not provide a substantial advantage compared to hydrolyzed collagen with 16% of amino acids as essential. With prolonged use, it may better maintain N equilibrium by preventing further increments in protein breakdown.
authors.affiliation: McGill Nutrition and Food Science Centre, Royal Victoria Hospital, Montreal, Quebec, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Gougeon
authors.forename: P B
authors.initials: PB
authors.lastname: Pencharz
authors.forename: E B
authors.initials: EB
authors.lastname: Marliss
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage* / Q000378:metabolism; D000704:Analysis of Variance; D015992:Body Mass Index; D002364:Caseins / Q000032:analysis; D003094:Collagen / Q000032:analysis; D018753:Diet, Protein-Restricted; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008715:Methionine / Q000378:metabolism; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism / Q000652:urine; D009587:Nitrogen Isotopes; D009765:Obesity / Q000378:metabolism* / Q000503:physiopathology; D014674:Plant Proteins, Dietary / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D030262:Soybean Proteins; D014364:Tryptophan / Q000378:metabolism; D014508:Urea / Q000652:urine
chemical_list: D000596:Amino Acids; D002364:Caseins; D009587:Nitrogen Isotopes; D014674:Plant Proteins, Dietary; D011506:Proteins; D030262:Soybean Proteins; D014364:Tryptophan; D014508:Urea; D003094:Collagen; D008715:Methionine; D009584:Nitrogen