The 'I Don't Care' singer, who has previously slammed criticism that she is too thin, hates the fact people are "judged" for their appearance and has encouraged people to seek new experiences without worrying about opinions over their size.
In a lengthy rant on Instagram, she wrote: "The other side of body shaming is skinny shaming. I think this happens just as much as shaming someone for being bigger. How often do you hear someone say, 'give that girl a sandwich', or 'she needs a good feed'?
"Everyone says they want the 'perfect body' and have so many body goals, but when a girl is just that bit too skinny, in your eyes, she gets judged.
"There is so, so, so, so much more to life than having the 'perfect body'. Every young person needs to understand that. Go travelling, learn about different cultures, be happy, fall in love and don't give a f**k about what people think."
And the 32-year-old singer urged people who care too much about their physique to "reconsider [their] attitude".
She added: "If your main goal in life is to be someone's 'body goals', you need to reconsider your attitude."