I have found that the gents who I have had the pleasure of seeing who are bigger in size have impeccable hygiene.
I have a gent I have seen many times he is big but has a lost a lot of weight recently is one of my favorite friends.He is always fresh,smells great,and dresses well.
We go to dinner,shows,etc and always have a great time.Few times of experiencing someone who was not fresh was guys who were not big at all.IMO I do not think size has anything to do with a person being clean or not.