my insurance company required me to go through six months of a supervised diet (supervised by either my PCP or a registered dietitian). Even though at first I thought it was going to be a giant PITA, I actually got a lot out of it - and I lost about 40 lbs to boot! She had me aim for about 2300 calories per day and add in regular exercise. I had to gradually increase my protein, gradually decrease my carbs, eat more fruits and vegetables. I also had to gradually wean myself off of caffeine and stop drinking carbonated beverages. I felt it really prepped me for the post-op life. Once I had surgery, the required change in eating wasn't nearly as drastic as it could have been.