Estimate of Resting Energy Expenditure by DXA in Boys of Different Nutritional Statuses

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 NWOB (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.