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Effect of weight loss on the rate of muscle protein synthesis during fasted and fed conditions in obese older adults.

ABSTRACT: Although weight loss ameliorates many of the metabolic abnormalities associated with obesity, there has been reluctance to prescribe weight loss in obese, older individuals because of the fear that it will cause debilitating loss of muscle mass and impair physical function. To gain insight into the mechanisms responsible for the weight loss-induced changes in muscle mass, we measured the rate of muscle protein synthesis (by using stable isotope labeled tracer methodology) during basal, postabsorptive conditions and during mixed meal ingestion in eight obese, older adults: (i) before weight loss therapy, (ii) ~3 months after starting the weight loss intervention (i.e., during the active weight loss phase), when subjects had lost ~7% of their initial body weight, and (iii) after they had lost ~10% of their body weight and maintained this new body weight for ~6 months (~12 months after starting the weight loss intervention). The basal muscle protein fractional synthesis rate (FSR) was not affected by weight loss. Mixed meal ingestion stimulated the rate of muscle protein synthesis, and the anabolic response (i.e., increase in the protein synthesis rate above basal values) was greater (P < 0.05) during negative energy balance and active weight loss at 3 months (0.033 ± 0.012%·per hour, mean ± s.e.m.) than during weight maintenance before and at 12 months of weight loss therapy (0.003 ± 0.003 and 0.008 ± 0.012%·per hour, respectively). We conclude that during dietary calorie restriction and weight loss in older adults, the rate of muscle protein synthesis is not impaired. Thus, the loss of muscle mass must be mediated predominately by adverse effects of dietary calorie restriction on muscle proteolysis.

SUBMITTER: Villareal DT

PROVIDER: S-EPMC3291735 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Project description:BackgroundObesity exacerbates the age-related decline in physical function and causes frailty in older adults; however, the appropriate treatment for obese older adults is controversial.MethodsIn this 1-year, randomized, controlled trial, we evaluated the independent and combined effects of weight loss and exercise in 107 adults who were 65 years of age or older and obese. Participants were randomly assigned to a control group, a weight-management (diet) group, an exercise group, or a weight-management-plus-exercise (diet-exercise) group. The primary outcome was the change in score on the modified Physical Performance Test. Secondary outcomes included other measures of frailty, body composition, bone mineral density, specific physical functions, and quality of life.ResultsA total of 93 participants (87%) completed the study. In the intention-to-treat analysis, the score on the Physical Performance Test, in which higher scores indicate better physical status, increased more in the diet-exercise group than in the diet group or the exercise group (increases from baseline of 21% vs. 12% and 15%, respectively); the scores in all three of those groups increased more than the scores in the control group (in which the score increased by 1%) (P<0.001 for the between-group differences). Moreover, the peak oxygen consumption improved more in the diet-exercise group than in the diet group or the exercise group (increases of 17% vs. 10% and 8%, respectively; P<0.001); the score on the Functional Status Questionnaire, in which higher scores indicate better physical function, increased more in the diet-exercise group than in the diet group (increase of 10% vs. 4%, P<0.001). Body weight decreased by 10% in the diet group and by 9% in the diet-exercise group, but did not decrease in the exercise group or the control group (P<0.001). Lean body mass and bone mineral density at the hip decreased less in the diet-exercise group than in the diet group (reductions of 3% and 1%, respectively, in the diet-exercise group vs. reductions of 5% and 3%, respectively, in the diet group; P<0.05 for both comparisons). Strength, balance, and gait improved consistently in the diet-exercise group (P<0.05 for all comparisons). Adverse events included a small number of exercise-associated musculoskeletal injuries.ConclusionsThese findings suggest that a combination of weight loss and exercise provides greater improvement in physical function than either intervention alone. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT00146107.).

Project description:BackgroundObesity impairs cognition and health-related quality of life (HRQOL) in older adults; however, the appropriate treatment of obese older adults remains controversial.ObjectiveThe objective was to determine the independent and combined effects of weight loss and exercise on cognition, mood, and HRQOL in obese older adults.DesignOne hundred seven frail, obese older adults were randomly assigned to a control, weight-management (diet), exercise, or weight-management-plus-exercise (diet-exercise) group for 1 y. In this secondary analysis, main outcomes were Modified Mini-Mental State Examination (3MS) and total Impact of Weight on Quality of Life-Lite (IWQOL) scores. Other outcomes included Word Fluency Test, Trail Making Test Parts A and B, and Geriatric Depression Scale (GDS) scores.ResultsScores on the 3MS improved more in the diet (mean ± SE: 1.7 ± 0.4), exercise (2.8 ± 0.4), and diet-exercise (2.9 ± 0.4) groups than in the control group (0.1 ± 0.4) (between-group P = 0.0001-0.04); scores in the diet-exercise group improved more than in the diet group but not more than in the exercise group. Scores on the Word Fluency Test improved more in the exercise (4.1 ± 0.8) and diet-exercise (4.2 ± 0.7) groups than in the control group (-0.8 ± 0.8; both P = 0.001). For the Trail Making Test Part A, scores in the diet-exercise group (-11.8 ± 1.9) improved more than in the control group (-0.8 ± 1.9) (P = 0.001); a similar finding was observed for the Trail Making Test Part B. Scores on the IWQOL improved more in the diet (7.6 ± 1.6), exercise (10.1 ± 1.6), and diet-exercise (14.0 ± 1.4) groups than in the control group (0.3 ± 1.6) (P = 0.0001-0.03); scores in the diet-exercise group improved more than in the diet group but not more than in the exercise group. In the diet-exercise group, peak oxygen consumption and strength changes were independent predictors of 3MS changes; weight and strength changes were independent predictors of IWQOL changes. GDS scores did not change.ConclusionsWeight loss and exercise each improve cognition and HRQOL, but their combination may provide benefits similar to exercise alone. These findings could inform practice guidelines with regard to optimal treatment strategies for obese older adults. This trial was registered atclinicaltrials.govas NCT00146107.

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Effect of weight loss on the rate of muscle protein synthesis during fasted and fed conditions in obese older adults.

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