I don’t know that I’d categorize weight loss surgery as “cosmetic.”
Wolf- Sorry I was unclear. The tshuva discusses cosmetic weight loss surgery, not health related weight loss surgery. I last saw the tshuva about 6 years ago so I could be mistaken, but I believe that R’ Moshe dismisses the shaila of health related weight loss surgery upfront by saying that whenever the health benefit of the surgery is expected to exceed the risk it is absolutely allowed.
Cosmetic surgeries are more problematic, because the guf (body) is on loan to us and not owned by us. Perhaps over Shabbos I will find time to look it up and provide an exact phrasing.