Some psychologists say that significance (in some way, shape, or form) is a universal need. Must we be significant in our appearance or physique? No, but it's certainly a way in which one can gain significance.That is nor true, everything that humans do or value, is delivered and created by the culture in which we live, the cosmovision. If you lived alone on this planet, you would not be worried about the things that you currently worry about.
I'm not as big as most of you, but I get some measure of satisfaction (arguably, significance) from being able to do a dozen or more strict bodyweight pull-ups at 54. This is something that, for me, certainly wouldn't be possible without the regimen of exercise and some conscious thought into my diet.