Image is everything in marketing, so it would help if you look the role you assume. Meaning a fat, out of shape person will never do as well as someone in great shape, if we are talking about selling things like supplements. Which is why you see very statuesque people in infomercials selling exercise machines, rather than fat people.
You can get away with a lot of things if you know how to talk, but your image will always be a major factor that affects the way you look, feel, interact and sell.