Tyra Banks is no stranger to body criticism.

And in a new interview, the former Sports Illustrated swimsuit models reveals how her weight has played a major part in her life.

tyra banks

Tyra earlier this year

"The summer I turned 11-years-old, I lost 30 pounds and I had a growth spurt," the 40-year-old says. "And it wasn't even supermodel thin. It was more than that. Some people thought I had an eating disorder."

Tyra did not have an eating disorder, and shares it was impossible for her to gain weight, so she was brought to a doctor to figure out what was happening to her body.

tyra banks

Tyra poses for Sports Illustrated in 1997

"I was poked with a lot of needles to see what was wrong with me. I was even misdiagnosed with gigantism," she says.

The stunner eventually gained weight and her womanly curves.

"Who would have thought that the girl who was forced to go to the hospital because she's so skinny would one day be called too fat?" she shares. "I know the pain of somebody who's too thin and the pain of somebody that people say is too big."

tyra banks

Tyra in 2004

As you may recall, the model was faced with backlash after an unflattering photo surfaced of the star looking larger than usual in a one-piece swimsuit in 2006. That same year, she wore said swimsuit on her self-titled talk show and famously told critics to kiss her "fat ass." (Watch below.)

Tyra, who launched the TZONE Foundation — a program to help mentor young girls — in 1999, hopes to inspire young women everywhere with her experiences.

tyra banks

Tyra in 2008

"That 11-year-old girl always lives inside of me," she says. "I show them [the TZONE girls] un-retouched photos of myself. They're like, 'Whoa.' But I tell them the truth. I want every girl to find their own beauty."

Her most important mantra these days? "Flaws are awesome – so, 'flawsome!' I love making up a word."

Tyra spoke exclusively with People.