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Effect of lifestyle changes on whole-body protein turnover in obese adolescents
Balagopal P, Bayne E, Sager B, Russell L, Patton N, George D
International Journal of Obesity and Related Metabolic Disorders 2003 Oct;27(10):1250-1257
clinical trial
5/10 [Eligibility criteria: No; Random allocation: Yes; Concealed allocation: No; Baseline comparability: Yes; Blind subjects: No; Blind therapists: No; Blind assessors: No; Adequate follow-up: Yes; Intention-to-treat analysis: No; Between-group comparisons: Yes; Point estimates and variability: Yes. Note: Eligibility criteria item does not contribute to total score] *This score has been confirmed*

OBJECTIVE: To investigate the effect of lifestyle changes on whole-body protein turnover (WBPT) in obese adolescents. DESIGN/METHODS: Randomized and controlled nonpharmacological intervention study of WBPT in obese adolescents using stable isotope dilution techniques. SUBJECTS AND MEASUREMENTS: We studied a total of 21 adolescents (11 boys and 10 girls, matched for their pubertal status) of which 15 were obese (age 15.8 +/- 0.4 y old and BMI 38.6 +/- 3.3 kg/m2) and six were lean controls (age 16.0 +/- 0.4 y old and BMI 21.3 +/- 1.2 kg/m2). The obese subjects were subjected to a randomized controlled lifestyle intervention program that involved moderate physical activity and diet changes for 3 months. A group of lean age-matched subjects was also studied at baseline to compare the WBPT in obese and lean adolescents. The studies were performed during a primed, continuous infusion of L-1-13-C-leucine. Leucine appearance rate (Leu Ra) was used as an index of whole protein breakdown and the nonoxidative portion of leucine disposal (NOLD) as an index of whole-body protein synthesis. RESULTS: The obese groups showed significantly higher body mass index (BMI), fat mass (FM), percent body fat (%BF), fat-free mass (FFM), resting energy expenditure (REE) and WBPT compared to the lean controls. The intervention program resulted in a redistribution of the parameters of body composition without apparent changes in BMI or body weight. There was a significant decrease in WBPT in the obese intervention group, but not in the obese control group. Insulin levels also decreased significantly in the obese group after intervention but not in the obese control group, whereas the glucose concentrations remained normal in all groups at baseline and also after intervention/or control. CONCLUSIONS: Results from the current study suggest: (i) abonormalities of protein metabolism occur early in the clinical course of obesity and (ii) these abnormalities are modifiable by moderate lifestyle changes in obese adolescents. The mechanism for these changes in WBPT in obese adolescents as well as their impact on specific cardiovascular risk factors and turnover of specific proteins will require further investigation.

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