A total of 28 adolescents with obesity will be recruited from our local inpatient pediatric obesity centers. Before their weight loss intervention the adolescents will complete two experimental visits. During the first visit, anthropometric and body composition measurements will be performed. Then the participants will be asked to complete a walking exercise on a treadmill during the second visit. Their energy expenditure and substrate oxidation will be assessed by indirect calorimetry. They will have to walk at 5 different walking speeds. Then, they will follow a 12-week weight loss intervention. By the end of this intervention, their body composition will be assessed and they will be asked to perform the same walking exercise. On a separate occasion (randomly assigned) they will have to repeat this walking exercise while carrying a load corresponding of their weight loss.
