Well, honestly theres as much skinny hate as fat hate in this world. I've been told all my life "You should eat more" and honestly anyone who truly knows me knows i eat a crap ton of food, i just have a very fast metabolism. (No jokes, if i eat something bad it wont even be an hour and i'm already creating a cauldron on the throne).
But in my experience i have stood up more for large people, and never had anyone stand up for me. I'm a small woman, im short and skinny, so its called PETITE.
But my point to those sims, the fat simmies, look proportionate. While the thin simmies don't. Thats my issue with them, theres many thin people thats as thin as those sims, and they look proportionate and have curves.