Girls actress and creator Lena Dunham has criticised people's obsession with her "ever-changing" body in a powerful message shared with fans.

In a lengthy Instagram post, the 30-year-old star, who’s championed body positivity in Hollywood for years, says her weight loss "isn't some sign I've finally given in to the voices of trolls".

“I’ve gone on red carpets in couture as a size 14. I’ve done sex scenes days after surgery, mottled with scars. I’ve accepted that my body is an ever changing organism, not a fixed entity- what goes up must come down and vice versa.”

Dunham went on to describe the motives behind her weight loss further: “Right now I’m struggling to control my endometriosis through a healthy diet and exercise.

"So my weight loss isn’t a triumph and it also isn’t some sign I’ve finally given in to the voices of trolls… I’m not handing in my feminist card to anyone… F**K IT. I refuse to celebrate these bulls**t before-and-after pictures.

"Don’t we have infinitely more pressing news to attend to?”

See Dunham’s post in full below:

Earlier this year, Dunham praised Glamour magazine for not airbrushing her figure.

"Throughout my teens I was told, in no uncertain terms, that I was f**king funny looking. Potbelly, rabbit teeth, knock knees -- I could never seem to get it right and it haunted my every move," she writes. "I posed as the sassy confident one, secretly horrified and hurt by careless comments and hostility. Let's get something straight: I didn't hate what I looked like -- I hated the culture that was telling me to hate it."

"When my career started, some people celebrated my look but always through the lens of 'Isn't she brave? Isn't it such a bold move to show THAT body on TV?'" she adds.

"Then there were the legions of trolls who made high school teasing look like a damned joke with the violent threats they heaped on, the sickening insults that made me ache for teen girls like me who might be reading my comments."

"Well, today this body is on the cover of a magazine that millions of women will read, without Photoshop, my thigh on full imperfect display," she points out. "Whether you agree with my politics, like my show or connect to what I do, it doesn't matter -- my body isn't fair game. No one's is, no matter their size, color, gender identity, and there's a place for us all in popular culture to be recognized as beautiful."

"Haters are gonna have to get more intellectual and creative with their disses in 2017 because none of us are going to be scared into muumuus by faceless basement dwellers, or cruel blogs, or even our partners and friends," she continues.

"Thank you to the women in Hollywood (and on Instagram!) leading the way, inspiring and normalizing the female form in EVERY form, and thank you to @glamourmag for letting my cellulite do the damn thing on newsstands everywhere today. Love you all."