Whole-body protein turnover in obese subjects during two very low energy diets of differing amino acid composition.
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.
Gougeon
R
R
McGill Nutrition and Food Science Centre, Royal Victoria Hospital, Montreal, Quebec, Canada.
Pencharz
P B
PB
Marliss
E B
EB
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
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