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Whole-body protein turnover and resting energy expenditure in obese, prepubertal children
Y Schutz1, C M Rueda-Maza, M Zaffanello
1Institute of Physiology, Faculty of Medicine, University of Lausanne, Switzerland. Yves.schutz@i.physiol.unil.ch
Insights
Childhood obesity increases protein metabolism rates, but this is explained by greater fat-free mass. Increased protein turnover in obese children correlates with increased resting energy expenditure (REE).
Area of Science:
- Pediatric Endocrinology
- Nutritional Science
- Metabolic Research
Background:
- Childhood obesity is a growing global health concern.
- Understanding its impact on protein metabolism is crucial.
Purpose of the Study:
- To evaluate protein metabolism kinetics in prepubertal children with obesity.
- To compare protein synthesis and breakdown rates between obese and lean children.
Main Methods:
- Cross-sectional study comparing 9 obese and 8 lean prepubertal children.
- Measured whole-body nitrogen flux, protein synthesis, and breakdown using [15N]glycine.
- Assessed resting energy expenditure (REE) and body composition.
Main Results:
- Obese children showed significantly higher absolute rates of protein synthesis and breakdown.
- These differences disappeared when adjusted for fat-free mass.
- Protein synthesis correlated significantly with fat-free mass and REE.
Conclusions:
- Increased protein turnover in obese children is linked to increased fat-free mass.
- This contributes to the higher resting energy expenditure observed in obese children.
- Findings highlight the metabolic adaptations in childhood obesity.
Background:
Obesity is becoming more frequent in children; understanding the extent to which this condition affects not only carbohydrate and lipid metabolism but also protein metabolism is of paramount importance.
Objective:
We evaluated the kinetics of protein metabolism in obese, prepubertal children in the static phase of obesity.
Design:
In this cross-sectional study, 9 obese children (x +/- SE: 44+/-4 kg, 30.9+/-1.5% body fat) were compared with 8 lean (28+/-2 kg ,16.8+/-1.2% body fat), age-matched (8.5+/-0.2 y) control children. Whole-body nitrogen flux, protein synthesis, and protein breakdown were calculated postprandially over 9 h from 15N abundance in urinary ammonia by using a single oral dose of [15N]glycine; resting energy expenditure (REE) was assessed by indirect calorimetry (canopy) and body composition by multiple skinfold-thickness measurements.
Results:
Absolute rates of protein synthesis and breakdown were significantly greater in obese children than in control children (x +/- SE: 208+/-24 compared with 137+/-14 g/d, P < 0.05, and 149+/-20 compared with 89+/-13 g/d, P < 0.05, respectively). When these variables were adjusted for fat-free mass by analysis of covariance, however, the differences between groups disappeared. There was a significant relation between protein synthesis and fat-free mass (r = 0.83, P < 0.001) as well as between protein synthesis and REE (r = 0.79, P < 0.005).
Conclusions:
Obesity in prepubertal children is associated with an absolute increase in whole-body protein turnover that is consistent with an absolute increase in fat-free mass, both of which contribute to explaining the greater absolute REE in obese children than in control children.