EXIT: Prospective Study of the Response to Exercise (EXIT)

Background :

Regular exercise is a cornerstone in the prevention and the management of comorbidities. Unfortunately, the metabolic benefit of exercise training is not universal and varies among individuals. A main factor likely to explain the exercise training variability is the lack of empirical evidence on the determinants of exercise training. A series of muscle-derived cytokines have recently been discovered that (1) are released during exercise and (2) exert positive effects on peripheral tissues. Irisin is one of these novel "myokines" and might contributes to the metabolic adaptations to exercise training.

Methods:

The investigators will perform a pilot cohort study in which obese adolescents will perform resistance exercise training for 6 weeks. The main exposure variable will be the acute release of irisin during resistance exercise. The main outcome measures will be the change in hepatic triglyceride content and glucose area under the curve during a 75g, 2-hour oral glucose tolerance test.

Study Hypothesis:

The primary overall hypothesis is that the change in plasma Irisin with a single bout of exercise will be associated with the metabolic adaptations to 6 weeks of resistance training, specifically, the reductions in hepatic triglyceride content and post-prandial glucose excursions, in obese adolescents.