Abstract
Abstract Aim: to estimate the resting energy expenditure (REE) of organ tissue components using Dual Energy x-ray Absorptiometry (DXA) in pubertal boys. The mass of components and REE were compared among groups of different nutritional statuses. Methods: a sample of 278 boys (13.7 ± 2.4 years old) was grouped according to BMI nutritional status for Brazilian children and adolescents1 such as Underweight (UW), Normal weight (NW), Overweight (OW), and Obese (OB). The REE of organ tissue components given by DXA was calculated using specific models for skeletal muscle tissue (SMT), adipose tissue (AT), bone tissue (BT) and residual tissue (RT) based on previous reports. The absolute and relative REE (REEDXA) of each component were statistically compared among groups. Results: No differences of total REEDXA were found among nutritional groups (F(3, 274)=0.071, p=0.976). When, however, specific REE was considered per component, differences were found for BT and REEBT between NW-OW (p=0.003) and NW-OB (p=0.048); in AT and REEAT for all the groups (p<0.001), except between UW-NW (p=1.000); in RT and REERT between NW-OB (p=0,022) and SMT and REESMT (p=0,039). Greater proportions of organ tissue of RT and high metabolic rates, were observed in the UW group (78.3%) in comparison to the OB group (60.7%). Conclusion: This approach provides a new opportunity to examine energy metabolism for individual differences of pediatric populations. It is an applicable strategy both to prescribe exercises and to administer diets to this population, as it reveals the magnitude of heat-producing body components.
Highlights
Conventional equations used to estimate resting energy expenditure (REE) consider generalized body dimensions without taking into account the different metabolic activities of tissues and organs[2]
Fat free mass (FFM) is considered the best predictor of REE5, because it consists of organs with a high metabolic rate such as the heart, spleen, kidneys, brain, liver, gastrointestinal tract[6] and large tissue structures
The results concerning the total or specific REEDXA for each component reveal that REE varies according to one’s nutritional status, with different and specific metabolic rates
Summary
Conventional equations used to estimate resting energy expenditure (REE) consider generalized body dimensions without taking into account the different metabolic activities of tissues and organs[2]. Fat free mass (FFM) is considered the best predictor of REE5, because it consists of organs with a high metabolic rate such as the heart, spleen, kidneys, brain, liver, gastrointestinal tract[6] and large tissue structures (skeletal muscle, and osteoarticular systems and ligaments). Both anatomically and metabolically, FFM is a heterogeneous compartment3, 4 , the specific metabolic rate of which can be measured, for instance, by the difference of arteriovenous concentration of tissues and blood flow[3]. Research has advanced understanding concerning the relationship between estimated metabolic rate and body composition (BC) to predict the REE of each component[8]
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