Protein metabolism in obese subjects during a very low energy diet (original) (raw)
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Protein sparing during treatment of obesity: ketogenic versus nonketogenic very low calorie diet
Metabolism, 1992
Although it is generally agreed that both ketogenic and nonketogenic very low calorie diets promote weight reduction, there is no consensus on a preference of one diet over the other in regard to protein sparing. In the present study, we compared the effects of isocaloric (600 kcal/d) and isonitrogenous (6 g nitrogen/d) ketogenic (low carbohydrate) and nonketogenic diets on parameters of protein and amino acid metabolism, in 16 morbidly obese women maintained on these diets for 4 weeks while confined to a metabolic ward. Cumulative urinary nitrogen excretion (g/4 wk) was significantly (P < .Ol) greater (246 f 6 w 207-C 12, mean-C SEM, n = 8). and cumulative nitrogen balance significantly (P < .02) more negative (-50.4 f 4.4 Y-18.8-C 5.7), during treatment with the ketogenic than with the nonketogenic diet. Plasma leucine concentration (pmol/ L) was significantly higher (P < .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (210 f 17 Y 160 f S), but not at day 28 (174 f 9 Y 148 f 8). Whole-body rates of leucine oxidation (mmol/h) were significantly higher (P < .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (1.29 f 0.20~0.92 f 0.10) and at day 28 (1.00 + 0.16 Y 0.75 f 0.10). Conversely, proteolysis, as measured by leucine turnover rate and urinary excretion of 3-methylhistidine, was not significantly different between the diets. We conclude that there is greater protein sparing by the nonketogenic than by the ketogenic very low calorie diet, and the mechanism appears to be greater protein synthesis.
Nitrogen metabolism at chronic low energy intakes
Nutrition Research, 1993
The response of animals adapted to moderate or severe energy restriction to supplements of free amino acids or protein is unknown. Lysine supplementation was examined because it is an amino acid frequently limiting in cereal-based diets. Male rats weighing ]15 g were assigned to one of seven diet groups. Animals were fed either a gluten-based diet or the gluten diet supplemented with adequate levels of lysine for 8 weeks. These diets were fed ad libitum or at 40% or 75% restricted levels. An additional group was fed a high gluten diet at the same energy level as the 75% restricted rats. Body weight, muscle weights, and adipose tissue were reduced relative to the level of restriction. Restricted groups adapted to the energy restrictions and exhibited either slow growth or stable body weight after 4 weeks on the respective treatments. Lysine supplementation increased muscle mass and improved nitrogen balance in the ad libitum and 40% restricted groups, but had no effect on the 75% restricted group. Excretion of 3-methylhistidine (3MH) was higher in the energy restricted animals after 7 weeks on the respective diets, and lysine supplements further increased 3MH losses. Plasma lysine levels were reduced by the food restrictions and unaffected by lysine supplements in the restricted animals. These findings indicate that the efficacy of lysine supplementation depends on the absolute level of energy intake, and a lysine supplemented diet may be detrimental to skeletal muscle mass at very low energy intakes. The data also showed that rats adapt to a 75% food restriction by achieving and maintaining nitrogen balance despite the increase in myofibrillar protein breakdown.
Low protein diets produce divergent effects on energy balance
Scientific Reports, 2016
Diets deficient in protein often increase food consumption, body weight and fat mass; however, the underlying mechanisms remain poorly understood. We compared the effects of diets varying in protein concentrations on energy balance in obesity-prone rats. We demonstrate that protein-free (0% protein calories) diets decreased energy intake and increased energy expenditure, very low protein (5% protein) diets increased energy intake and expenditure, whereas moderately low protein (10% protein) diets increased energy intake without altering expenditure, relative to control diet (15% protein). These diet-induced alterations in energy expenditure are in part mediated through enhanced serotonergic and β-adrenergic signaling coupled with upregulation of key thermogenic markers in brown fat and skeletal muscle. The protein-free and very low protein diets decreased plasma concentrations of multiple essential amino acids, anorexigenic and metabolic hormones, but these diets increased the tissu...
Metabolic effects of very low calorie weight reduction diets
Journal of Clinical Investigation, 1984
A randomized comparison trial of two very low calorie weight reduction diets was carried out for 5 or 8 wk in 17 healthy obese women. One diet provided 1.5 g protein/kg ideal body weight; the other provided 0.8 g protein/kg ideal body weight plus 0.7 g carbohydrate/kg ideal body weight. The diets were isocaloric (500 kcal). Amino acid metabolism was studied by means of tracer infusions of L-[1-'3C]leucine and L-['5N]alanine. After 3 wk of adaptation to the diets, nitrogen balance was zero for the 1.5 g protein diet but -2 g N/d for the 0.8 g protein diet. Postabsorptive plasma leucine and alanine flux decreased from base line by an equal extent with both diets by -20 and 40%, respectively. It was concluded that protein intakes at the level of the recommended dietary allowance (0.8 g/kg) are not compatible with nitrogen equilibrium when the energy intake is severely restricted, and that nitrogen balance is improved by increasing the protein intake above that level. Basal rates ofwhole body nitrogen turnover are relatively well maintained, compared with total fasting, at both protein intakes. However, turnover in the peripheral compartment, as evidenced by alanine flux, may be markedly diminished with either diet.
Brazilian Journal of Medical and Biological Research, 2001
This study examined if leucine, arginine or glycine supplementation in adult obese patients (body mass index of 33 ± 4 kg/m 2) 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 15 N-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 ± 24 during the nonsupplemented diet intake and 39 ± 10, 44 ± 22 and 58 ± 35 during the leucine-, glycineand arginine-supplemented diet intake, respectively; protein synthesis (gN/9 h) was 57 ± 24, 36 ± 10, 41 ± 22 and 56 ± 36, respectively; protein breakdown (gN/9 h) was 51 ± 24, 34 ± 10, 32 ± 28 and 53 ± 35, respectively; kinetic balance (gN/9 h) was 3.2 ± 1.8, 4.1 ± 1.7, 3.4 ± 2.9 and 3.9 ± 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.
AJP: Endocrinology and Metabolism, 2007
It is unclear whether the rate of weight loss, independent of magnitude, affects whole body protein metabolism and the synthesis and plasma concentrations of specific hepatic secretory proteins. We examined 1) whether lean men losing weight rapidly (starvation) show greater changes in whole body protein kinetics, synthesis, and circulating concentrations of selected hepatic secretory proteins than those losing the same amount of weight more slowly [very low energy diet (VLED)]; and 2) whether plasma concentrations and synthetic rates of these proteins are related. Whole body protein kinetics were measured using [1-13C]leucine in 11 lean men (6 starvation, 5 VLED). Fractional and absolute synthetic rates of HDL-apolipoprotein A1 (apoA1), retinol binding protein, transthyretin, α1-antitrypsin (α1-AT), and transferrin were measured using a prime-constant intravenous infusion of [13C2]glycine. Compared with VLED group, the starvation group showed greater increases (at a 5% weight loss) ...
Clinical Nutrition, 2007
Background & aims: Patients with type 2 diabetes (T2DM) tend to loose more lean body mass during both long-term weight reduction and short-term very-low-calorie diet. We ask what factors influence protein loss during acute starvation in T2DM. Methods: In a prospective in-hospital observational study, we compared 10 subjects with T2DM and 10 age-weight-sex matched obese controls (OB) during 60 h of fasting and used frequent blood sampling and indirect calorimetry to describe metabolic and endocrine response. We analyzed factors influencing nitrogen balance using stepwise multiple regressions. Results: Despite comparable pattern of plasma insulin, free fatty acid, 3-hydroxybutyrate and almost identical behavior of growth hormone axis, our T2DM subjects remained hyperglycaemic and in contrast to OB subjects they failed to reduce the rate of protein oxidation, even though muscle protein breakdown rate declined similarly in both groups. Regression analysis revealed that protein oxidation rate in T2DM group was enhanced by hyperglycemia and sympathetic activity and suppressed by circulating insulin and 3hydroxybutyrate. Liver insulin resistance increases peripheral insulin concentrations and enhances the conversion of non-esterified fatty acids (NEFA) to ketones and thus it might be a protein-saving factor.