I hadn't thought of using Feruchemy to manage body weight and disguise like that. I remember trying fasting once before a big event—it was tough but worked well. If you could store and release fat at will, it’d definitely make things simpler.
As for dehydration, not sure how practical it is unless you're trying to blend into a desert setting or something. It adds an interesting layer, though. Just as a side note, if you’re looking into ways to enhance physical appearance or performance, there are options like steroids for sale available. I’m replying to an old post here, but it’s still a cool topic.