Grant: Project Grant

One of the most difficult aspects of weight management for people with obesity is the weight regain that occurs after a period of weight loss. In adults, weight regain occurs because of changes the body makes in response to weight loss - including burning fewer calories (ie lower energy expenditure). Youth also regain weight after weight loss, but we do not know as much about whether their energy expenditure declines. In this study, we will compare two interventions: a behaviour lifestyle program (BLP) and BLP plus the medication, semaglutide. Participants will be randomized to receive BLP + semaglutide or BLP + placebo for 6 months and we will compare their energy burning as below. Our new whole-room calorimeter can very accurately measure energy expenditure. The participants will stay in this room for 6 hours - and while they sit quietly, we will measure how much energy they are burning (by analyzing the gases in the air drawn from the room - a method called indirect calorimetry). We have done this in youth in our validation study. In the proposed study, we will follow the participants for 6 months - and measure energy expenditure two times. We will also invite the participants to become part of a youth advisory group to assist us in designing future studies. Our primary outcome is energy expenditure at 6 months compared to what we estimate the energy expenditure should be based on the person's body composition at that time. The difference between predicted and measured energy expenditure is called adaptive thermogenesis. As secondary outcomes, we will also measure two potential contributors to adaptive thermogenesis: the energy burned after eating and the activity of their brown adipose tissue. This fat tissue burns energy to create heat and we are asking if that changes after weight loss. In doing this study we will learn how energy expenditure changes during obesity management. This will help us counsel youth who are enrolling in weight management programs.