Lena Dunham's recent Instagram post has gone viral for proving that there is no truth to the old myth that skinny people are happier.

The Girls star posted two before-and-after photos of herself, one skinnier and one heavier, to prove an important point and her message resonated with tens of thousands of people around the world.

"On the left: 138 pounds, complimented all day and propositioned by men and on the cover of a tabloid about diets that work. Also, sick in the tissue and in the head and subsisting only on small amounts of sugar, tons of caffeine and a purse pharmacy," she wrote alongside the photos.

"On the right: 162 pounds, happy joyous & free, complimented only by people that matter for reasons that matter, subsisting on a steady flow of fun/healthy snacks and apps and entrees, strong from lifting dogs and spirits.

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"Even this OG body positivity warrior sometimes looks at the left picture longingly, until I remember the impossible pain that brought me there and onto my proverbial knees. As I type I can feel my back fat rolling up under my shoulder blades. I lean in."

Dunham has previously opened up about her battle with endometriosis, an illness that causes her severe pain.

The post received nearly half a million likes in just a day and received more than 14,000 comments.

"This really resonated, thank you," commented singer Demi Lovato.

"Love you so hard," actress Busy Philipps commented.

"Girls and women: this is what true freedom looks like," actress Megan Mullally added, while singer Katy Perry called it "powerful".