ABSTRACT
This study examined if leucine, arginine or glycine supplementation in adult obese patients (body mass index of 33 + or - 4 kg/m²) consuming a Brazilian low energy and protein diet (4.2 MJ/day and 0.6 g protein/kg) affects protein and amino acid metabolism. After four weeks adaptation to this diet, each subject received supplements of these amino acids (equivalent to 0.2 g protein kg-1 day-1) in random order. On the seventh day of each amino acid supplementation, a single-dose 15N-glycine study was carried out. There were no significant differences in protein flux, synthesis or breakdown. The protein flux (grams of nitrogen, gN/9 h) was 55 + or - 24 during the nonsupplemented diet intake and 39 + or - 10, 44 + or - 22 and 58 + or - 35 during the leucine-, glycine- and arginine-supplemented diet intake, respectively; protein synthesis (gN/9 h) was 57 + or - 24, 36 + or - 10, 41 + or - 22 and 56 + or - 36, respectively; protein breakdown (gN/9 h) was 51 + or - 24, 34 + or - 10, 32 + or - 28 and 53 + or - 35, respectively; kinetic balance (gN/9 h) was 3.2 + or - 1.8, 4.1 + or - 1.7, 3.4 + or - 2.9 and 3.9 + or - 1.6. There was no difference in amino acid profiles due to leucine, arginine or glycine supplementation. The present results suggest that 0.6 g/kg of dietary protein is enough to maintain protein turnover in obese women consuming a reduced energy diet and that leucine, arginine or glycine supplementation does not change kinetic balance or protein synthesis