The situation is not comfortable. However, and I hope you take this in the spirit it is meant. From one big girl to another, do you believe that people at your church, work, etc. don't know that you are...well, fat?
What difference does it really make if people know you are considering or have had LAP-BAND® surgery? You are acting like trying to improve your health is a shameful thing that needs to be kept private.
From someone who is newly banded, I can tell you that it's no "magic bullet"; I'm working my butt off! I would use the opportunity to "flip the script" on this gadfly and if someone mentions it to you say, "Yes, I am considering LAP-BAND® surgery. It's a drastic step but I believe it will help me acheive my personal health goals." Then smile as you deliver the final, disarming but sincere zinger..."thank you so much for your concern; it means so much to me to know that you care!"
I personally haven't hid a thing from anyone - not my coworkers, family or friends. It was that right thing to do. Everyone has been like my personal cheerleaders.
As a manager of a large dental practice, I would immediately terminate any employee who was divulging personal info to outside sources. You should schedule a meeting with the doc and the office manager. Ask them what they plan to do about the situation and insure that they follow up. Trying to sue the doc or the office is *not* the way to endear yourself to medical community, trust me. You'd be hard pressed to find a doc that would take you on after that.
Good luck!