Unless they are loaded to the nines with magical items and/or spells, does an obese adventurer make sense?
First I dont think you using the word obese is a coincidence, I think you are hating on fat people by using a term that is more extreme. Second, it's like saying that it wouldn't make sense to have a small adventurer because they would be at a disadvantage. I can recommend you a series of books called Lord Of The Rings that has a thing or two to say about it.
Also have you never seen a person who is overweight but still an athlete? Many basketball players or american football players, even rugby players are like that and they can run faster than you.