People can do whatever they want with their own bodies. There is nothing wrong with wanting to lose weight. Or gain it. Or sustain it.
That’s the thing: it’s THEIR choice and no one else’s. You have your own body to criticise; though I wish you wouldn’t. I hope that people can learn to take these feelings of wanting to tear someone down and use it to build them up instead. If you feel like destroying something, destroy the idea that you have to be beautiful to be worthy. Destroy the idea that you have to be beautiful to anyone other than yourself. Destroy the idea that harming people is okay, because it absolutely is not okay.
Use your words and actions for good things instead of useless hate. That is all.