How can I convince my doctor to allow me to have gastric byp surgery?

I'm 27 years old and I weigh more than 270 pounds. I've been battling with my weight my whole life. I'm a well educated individual and I know the risks involved with this procedure. My blood pressure is unstable, I'm pre-diabetic, and my knees and hips are starting to give out. My doctor seems to think that the solution to my weightloss is to switch to 1% milk and drink a gl a water before every meal. I know that this surgery is only a tool in a much greater process to change my life, but how can I convince her that this is the best choice for me?