Physical Exercise Prehabilitation Program in MEtabolic SuRgery

The goal of this clinical trial is to learn if an exercise program before bariatric surgery works to treat obesity, could improve physical condition and weight loss before bariatric surgery and induce a lifestyle behavior change. The main questions it aims to answer are: * Does a supervised exercise program lead to improved physical condition prior to bariatric surgery? * Does a supervised exercise program prior to bariatric surgery lead to reduced surgery related complications? * Does a supervised exercise program prior to bariatric surgery lead to maintained lifestyle changes after surgery? Participants will: * Receive either no training program or physical exercise training program twice a week, supervised by a physical therapist, for a duration of 8 weeks. * Have their fitness measured at the start and at the end of the 8 weeks, measured with a six minute walking test. * Fill in a survey on their perceived quality of life and exercise habits at the start of the trial, and at 1 year after surgery.