Honestly, Red and Green having the best bodies makes the most sense, because they're the ones who battle and train all the time--and we definitely know that Green, at least, trains his body as well as his Pokemon, and it isn't too much of a stretch to assume Red picked up on it. It's also important to remember that Red is sixteen by FR/LG, making PUBERTY also a deciding factor.

Now if, say, Ruby were to whip off his shirt and reveal SEXY PECS, then I would call bullshit. Well, I'd call bullshit through my mouthful of drool. 8Db