It sounds just like my good old friend, "self-delusion". I'd look in the mirror, seem a bit chunky, and just tell myself I'm fine, just heavy-set and need to lose a "few" kilos sometime later, "...my proportions are fine!". I think it's sort of got to do with how people compare themselves with ideal models. In my case the model was some poorly-defined "inside-self" rather than a standard normal healthy lean male form.
Now that I've lost a lot of weight I realise what an idiot I was in the past to not compare myself to the optimum shape and weight for good health and social acceptance (yeah, sounds facile, but that's a very important factor to happiness).