There is so much pressure around to look the way the media tells us we should look. Unfortunately this is now ever growing for men too. When we talk about equality I don't think this is quite what we had in mind. We wanted it to get better for women not worse for men.
The media portrays a thin, white, blonde binary cis woman as the ideal women should all aspire for. If you happen to resemble this closely by any which means you may consider it a privilege. It is a privilege bestowed upon you by the cis het white men running the show but it is still a privilege of sorts. There are different kinds of beauty privileges and body privileges that can give you a leg up in various parts of your life. Or fetishize you in others. If you happen to be an alternative chic but still fulfill certain beauty credentials you may experience the phenomenon affectionately dubbed "fuck a freak".
Obviously people commenting on skinny bodies isn't cool. Being constantly told you're too thin, should put on weight etc. must be a horrible thing to hear. And any pressure to stay a certain way is awful. However whilst you are thin this affords you certain opportunities, your body is quite simply lauded. It may not be a positive thing but looking a certain way particularly as a white woman will give you a foot up in life. Until you age and it all goes tits up, or down if you'd rather.
The thing about privilege is, you won't necessarily see that you have it. But as a woman you will be measured and you will be found wanting.