Gaining

When I was married, I was with my 5'3", 300 pound wife at the doctor for a routine checkup. After taking all the vitals plus a few more, he congratulated her on being one of the healthiest people to visit his office.... And then turned right around and scolded her for her weight, saying how unhealthy she was. I about died of laughter.

Your doctor has "done his duty". Talked to you about your weight, given you a prescription. He may be assuming you want to lose weight but "can't". He probably thinks he's being helpful. He can't make you take the pills and if he continues to mention it, just politely say that you are aware of it and if you ever decide to lose weight, you'll do it without pills or you'll discuss it with him then, or something like that, or maybe even say you focus more on all the other vitals and aren't as concerned about weight as long as all your vitals are good.

You really truly can not weigh your health.

I personally knew two people who died from Fen/Phen when it was popular. I also know of countless people who have died from WLS. Some died on the operating table, some died 10 years after the surgery after battling the complications. I can see not trying to gain on purpose for your health, but losing only causes regain in the future.