Acute simulated weight gain might not increase the energy cost of walking in adolescents with obesity.

Introduction: This work aims at evaluating the adaptations of the energy cost of walking (Cw) to simulated weight gain at different walking speeds in adolescents with obesity.

Methods: Substrate use and Cw were evaluated during a graded walking exercise (4 × 5min at 0.75, 1, 1.25, 1.5 m.s^-1) performed under three randomized body weight conditions (BW-conditions): (i) at the adolescents' body weight (BW + 0%) or with a simulated weight gain of (ii) 5%(BW + 5%) and (iii) 10%(BW + 10%), in 18 adolescents with obesity (14.2 ± 1.4 years, BMI:33.86 ± 2.55 kg.m-²). Body composition was assessed by absorptiometry and perceived exertion rated after every walking speed stage.

Results: EE in absolute or relative to BW and FFM was different between BW-conditions (p = 0.017, 0.006 and 0.007, respectively) being lower on BW + 5% than BW + 10%. Gross Cw (absolute, relative to BW and fat-free mass) showed overall speed (p < 0.001) and BW-conditions effects, being lower on BW + 5% compared with BW + 10% (p < 0.001). Net Cw (absolute, relative to BW and fat-free mass) showed a significant speed effect (<0.001) but no BW-conditions nor interaction effect.

Conclusion: While EE and Cw have been shown to decrease in response to weight loss, potentially as a way to save stored energy and limit further weight loss, inverse adaptations do not seem to occur with increased acute simulated weight gain in weight stable adolescents with obesity.