Effects of Bariatric Surgery on Different Compositions of Trunk Fat and Mechanisms

This is a prospective, single-center, observational study to explore effects of bariatric surgery on different compositions of trunk fat and mechanisms. The primary outcome is effects of bariatric surgery on different compositions of trunk fat evaluated with MRI for patients pending bariatric surgery before and 3 months after surgery. The secondary outcome is the associations of trunk fat reduction with improvement in metabolism indicators. Before patients are enrolled in this observational study, the researchers will do a detailed screening of the subjects based on the inclusion criteria and the exclusion criteria to determine if the patients are appropriate for the study. Patients who meet the conditions of the study will be required to sign an informed consent form.