Back surgery

... and on the side of what ncboller and villae mentioned - your doctor should be the one managing it with assistance form a dietitian.
Do not mean to ruff your feathers but you are heavy and at that size you don't just throw a "hey - loose 50 pounds and come back to see me"!

In 2012, I had a spinal fusion between my Lumbar and sacral vertebra. I straight-up asked my surgeon about my weight. He told me that because of my weight I would require more anesthesia. He said that this would marginally increase my surgical risk. In his opinion, further delaying the surgery was a greater risk. Because of the pain my Mobility was severely limited. Lack of Mobility leads to weight gain, which leads to more compression on the spinal column. Also he was concerned that if I gained even more weight, I would become at higher risk for developing diabetes and heart disease. Long story short, I had the surgery and everything went perfectly. I have to agree with the others that this doctor needs to be replaced as your doctor. It's perfectly fine if he feels that your weight is too great of a risk surgically, but any Doctor Who would tell you to lose that much weight in that short amount of time does not have your best interest. Feel free to add me if you'd like to commiserate about back issues. I don't know what type of surgery you're looking at having, or what type of problem you are attempting to correct, but unfortunately I have a boatload of experience in that area.