Why do people look down on others in terms of body shape and size?.?

I have noticed that SOME people look down on skinny people calling them sticks and men. I feel that it is not our fault that we are a size 0 or 1. Seriously, because of the questions i get( like how old are you?, you probably weigh less than 100 right?) had made me eat so much like whatever it can be qualified to. Why cant people understand that it is not your fault (in most cases) since it could probably be hereditary. Really, i am tired of crying or hiding my body because of this and have decided to embrace it. Now, i love it and have closed my ears to hearing degrading words. So any of you who fall between this category, please embrace your body and know that IT IS WELL. Much luv!