Have you ever wondered why so we are glad the beauty of nature? Why animals and plants seem so beautiful? Everything in nature is effective and is not affected, otherwise he would not be able to live. Hippopotamus, which seems so heavy and clumsy, was faster than in its natural state than one can be, and it's really beautiful. Meanwhile, a legless and slippery snake moves so beautiful and fast that we could do, but I wonder how he manages. 
The very idea of beauty inseparable from rationality. It is rationality that makes us create lovely cars and stylish ocean ships and admire the men and beautiful women, muscular body shape. Inextricable link between rationality and beauty is a rule for all living things and the main indicator of quality. That is why in our desire to be selected by the opposite sex, we try to look attractive.
All bread is baked in the oven, so people differ in their natural form. Some of them are naturally thin, others hard. But the fashion changes from time to time and presses its standards for all. How can I find some of its measures for the beauty and attractiveness? Where is the border between shortweight, average weight or overweight? Or how is it? Of course there is. The only measure, because it is still defined by rationality or, roughly speaking, health care, energy and mobility.