The response of whole-body protein turnover to feeding in obese subjects given a protein-free, low-energy diet for three weeks.
Rates of whole-body protein turnover were measured by constant infusion of [1 14C]leucine in four obese subjects receiving a normal diet (approximately 2000 kcal and 70 g protein ) and again after 3 weeks on a low-energy, protein-free diet (500 kcal of glucose syrup). During the first 12 h of infusion subjects were given equal, hourly portions of the appropriate diet, and for the next 12 h they fasted. With the normal diet fasting was accompanied by a fall in rates of protein synthesis and leucine oxidation and a rise in protein breakdown, but these changes were abolished by the protein-free diet. In addition, during the 3 weeks of protein deprivation there was an adaptation in which all rates fell below those observed during fasting after the normal diet. The second infusion of [1 14C]leucine was prolonged beyond 24 h in three of the subjects and dietary protein was reintroduced as equal, hourly portions of a low-energy, protein-containing diet (500 kcal, 50 g protein). Protein synthesis rates did not alter but there was a pronounced fall in protein breakdown and an increase in leucine oxidation. This different response to protein intake was discussed in relation to the adaptation brought about by 3 weeks of protein deprivation.
D000222:Adaptation, Physiological; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D005215:Fasting; D005260:Female; D005502:Food; D006801:Humans; D007930:Leucine / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*
D004044:Dietary Proteins; D011506:Proteins; D007930:Leucine; D009584:Nitrogen