A group of twenty obese men (BMI≥35 kg*m-2) will be assigned to Fatmax group or to adapted HIIT group. Both groups will perform 8 cycling-sessions matched for mechanical work spread over 14 days [40-50 min continuous exercise at ~60-70% of the maximal heart rate (Fatmax) or 10x60-s cycling intervals a ~90% maximal heart rate interspersed with 60-s recovery (HIIT)]. Aerobic fitness and fat oxidation rates (FORs) during exercise will be assessed prior to and following the training with a maximal incremental test. Blood samples will also be drawn to determine hormones and plasma metabolites levels. Insulin sensitivity was assessed by the homeostasis model assessment of insulin resistance (HOMA).