The aim of this study is to assess whether the energy you burn daily increases after you have bariatric surgery. Until now, there hasn't been an effective way of measuring all activity on a daily basis. Physical Activity Monitoring System (PAMS) has been created just for this purpose. PAMS is a garment that can be worn under your clothes, that records body position and movement through space. We will use the PAMS along with special water to measure your total daily energy expenditure right before surgery, and again 6 months and 24 months after surgery.