The fat Buddha became a symbol, is all. By all historical accounts, we either have no idea what the Buddha looked like, or he was much less rotund. The infamous Buddha pose is, if anything, a representation of happiness, not a statement on a religious figure's BMI.
Beyond that, obesity isn't always looked down upon. Or rather, it shouldn't be when pertaining to religious matters. Would you discount someone's opinion because of their weight? Unless the matter on which they spoke was, say, fitness, I hope your answer would be a resounding "no."
Your admiration of physical perfection is, perhaps, itself admirable. However, it has no bearing on spirituality. Nor happiness, for that matter, which was one of the primary virtues espoused by the Buddha's philosophy.
In summary, this is a silly notion. We might as well deduct points from Jesus because he didn't have hella-ripped abs.
Also, wrong forum.