The prevention and management of pediatric obesity require a thorough understanding and consideration of the various components of energy balance (i.e., intake and expenditure) and their interactions. Total energy expenditure (TEE) consists of resting metabolism (RM), energy expenditure induced by physical activity (EEPA), and dietary thermogenesis (DTE). While RM and EEPA are the two main contributors to TEE, DTE is often overlooked, even though it can account for around 10% of our daily energy expenditure. In fact, few studies have prioritized the evaluation of the thermic effect of food (TEF), defined as the increase in energy expenditure above the basal metabolic rate when fasting, despite the fact that it accounts for about 10% of total daily energy expenditure. It has been suggested that TEF may play a role in the development or maintenance of obesity. Some studies indicate a reduction in TEF in individuals living with obesity, possibly due to lower postprandial activation of the sympathetic nervous system, thereby limiting the thermogenic response after meals. Conversely, several studies have reported no decrease in TEF in individuals living with obesity. Due to these conflicting results, no consensus has been reached on the response of TEF in individuals with obesity compared to those of normal weight. While our team recently conducted a systematic review of the literature in this area, identifying a glaring lack of evidence, the few results available suggest a potential reduction in TEF in children and adolescents with obesity, contributing to minimizing the optimization of their daily energy balance. In their study, Maffeis and colleagues show, for example, a significantly reduced TEF in adolescents with obesity compared to their normal-weight counterparts, despite a higher-calorie test meal adapted to their energy needs. These results are consistent with those proposed by Salas-Salvado the following year, which suggest a reduced TEF in obese adolescents, associated with their percentage of body fat.This research suggests the need to consider the effects of weight status, body composition, and the caloric composition of a meal in order to better understand TEF in this population. Furthermore, while our team has repeatedly highlighted adaptations in resting metabolism and exercise metabolism in response to weight loss in obese adolescents, the TEF responses to these interventions have also been little studied in adolescents. To our knowledge, there is only one study that has qualitatively assessed this adaptation of TEF to weight loss in this population. According to the authors, while DHEA was reduced at baseline in obese adolescents compared to their normal-weight counterparts, weight loss appeared to increase DHEA levels, but this remains to be confirmed. In this context, the objective of this study is to evaluate the effects of weight loss on dietary thermogenesis in obese adolescents. It will also compare the thermogenesis of these adolescents before weight loss with that of adolescents of normal weight.
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Postprandial energy expenditure (PEE)
Timeframe: 3 months for normal weight adolescents and 6 months for adolescents with obesity