Plastic surgery is for many just a four weeks vacation. Just looking better when they return. Brazil has the best reputation.
Obesity surgery is different. You only do that to get lower cost if you have to pay yourself for this procedure. Many in USA (and UK) have no insurance or do not qualify under their current health plan. So if you need/want the surgery and you have to pay yourself then Brazil, Argentina, Mexico and other countries are options. Flying 8 -15 hours to save 50-60% is then not much of an issue.
From the websites I have visited (like
Weight Loss Surgery in Brazil - Affordable Bariatric Surgery ), it seems you need about two weeks to get the surgery done and checked (only 2-3 days in the hospital).