Fans know that Whitney Thore wasn’t always the size she is now, and her weight gain can be attributed to her disease.

At just 20 years old, the star of My Big Fat Fabulous Life was diagnosed with Polycystic Ovary Syndrome — or PCOS — after she put on 100 pounds in nine months. Doctors couldn’t figure out what was causing her rapid weight gain and she continued to pack on the pounds. One year and another 100 pounds later, she was finally diagnosed with the disorder and since then, she’s been outspoken about it and how it affected her body image. She recently got candid about her PCOS when a doctor sent her a nasty letter shaming her for her weight.

MORE: 'My Big Fat Fabulous Life' Star Whitney Thore Twerks on Instagram — See Her Dancing With Her Mom, Babs!

"Gaining such a large amount of weight in such a small time is traumatic, to say the least. PCOS has caused acne and hair growth all over my face,” the body positivity activist wrote on Instagram. “It puts me at an increased risk for most major health problems and has left my ovaries riddled with cysts and caused me not to bleed for years and years at a time. Since being diagnosed, I have lost 100 pounds in [eight] months, gained it back, and still struggled with bulimia and disordered eating.”

PCOS is a hormonal disorder that affects one in 10 women. It occurs when a woman develops multiple small cysts on her ovaries, according to WebMD. The cysts are not threatening, but they cause hormonal imbalances and symptoms can include irregular periods, acne, thinning hair on the scalp and growth of hair on the face or the body, depression, fertility problems and weight gain or trouble losing weight — which is because the condition causes the body to build up insulin resistance.

MORE: 11 Times 'My Big Fat Fabulous Life' Star Whitney Thore Proudly Showed Off Her Body on Instagram!

But even though she is 200-plus pounds heavier than she used to be, Whitney constantly reminds people that she loves the body she’s in now. She has no desire to get back to her previous weight because she learned how to love and accept herself and her body.

“The woman I am now can dance with reckless abandon. She can frolic in a bikini. She can demand love and respect that is not contingent on her dress size," Whitney declared in an Instagram post. "The woman I am now can LIVE, knowing that I am completely deserving of every single wonderful thing this world has to offer."