Investigating Factors Related to Resting Energy Expenditure in Children with Obesity

Abstract

Background: Pediatric obesity affects approximately one in three Canadian children and is associated with adverse health outcomes that often persist into adulthood. While behavioral interventions can yield modest short-term reductions in weight, long-term maintenance is a challenge. Obesity is caused by an imbalance between energy intake and energy expenditure, therefore a key component of energy balance dynamics is resting energy expenditure (REE). This thesis aims to investigate factors influencing REE in children with obesity through a scoping review, cross-sectional analysis, and preliminary longitudinal evaluation. Methods: A scoping review was conducted following PRISMA-Sc guidelines to synthesize evidence on determinants of energy expenditure (EE) in children with obesity. A cross-sectional study was performed in 33 participants (20 with obesity, 13 with normal BMI) aged 8–17 years to evaluate associations between age, pubertal status, and REE per fat-free mass (REE/FFM) using whole-room indirect calorimetry (WRIC), dual-energy X-ray absorptiometry (DXA) and/or bioelectrical impedance analysis (BIA). Finally, preliminary 6-month follow-up data from 9 participants enrolled in a pediatric weight management program were assessed to examine changes in REE/FFM over time in children with obesity. Results: The scoping review (total n = 100 studies) revealed that although absolute REE is elevated in children with obesity, REE/FFM is generally comparable to children with normal BMI, and that more research is needed to determine the relationship between age and pubertal status on REE/FFM. Cross-sectional analyses demonstrated no significant association between age or pubertal status and REE/FFM; however, significant interaction effects with age and pubertal stage with obesity status suggest weight status modifies these relationships. At 6-month follow-up, there were no significant differences between baseline and 6 month REE/FFM, total body fat % and other body composition parameters. In addition, none of the 9 longitudinal study participants who completed their 6 month follow up achieved a clinically significant reduction in BMI z-score (≥0.25). Conclusion: Absolute REE differs when comparing children with and without obesity. However, REE/FFM in children with obesity does not differ when compared to children without obesity, though its relationship with developmental factors such as age and pubertal status may differ based on weight status. These findings highlight the need for adequately powered longitudinal studies to clarify age- and puberty-related changes in energy expenditure and to inform more effective long-term obesity treatment strategies.