I used to work out a lot with a trainer and had a good amount of muscle. Through some various circumstances I ended up gaining a lot of weight. Then I lost it all on a Keto diet, and then once I went off the diet I started gaining weight faster than ever before, and regained everything I'd lost (over 200 pounds) and added another hundred pounds in two years. In four years I went from 6'4", ~280 pounds to 6'4", 702 pounds and from XXL shirts to 9XL. I still have decent muscle under the bulk. I'm working out with a trainer a couple times a week to keep muscle and gain stamina to support my size!