When the supermodel and her mother, Carolyn London, launched a program in 1999 to mentor young girls – the TZONE Foundation – Banks realized the importance of sharing the insecurities she experienced while growing up.
"The summer I turned 11 years old, I lost 30 lbs. and I had a growth spurt," Banks, 40, tells PEOPLE in this week's issue. "And it wasn't even supermodel thin. It was more than that. Some people thought I had an eating disorder." She didn't.
"There was nothing I could do to gain weight," she says, "It was in the 1980s during the Ethiopian famine, and I got a lot of comments."
Banks had to visit the doctor repeatedly. "I was poked with a lot of needles to see what was wrong with me. I was even misdiagnosed with gigantism," she says.
Gradually, as she grew up, she started to gain weight and fill out.
"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?" says Banks. "I know the pain of somebody who's too thin and the pain of somebody that people say is too big."
"That 11-year-old girl always lives inside of me," says Banks, who works with young women on everything from self-esteem to the importance of elocution and entrepreneurship.
"I show them un-retouched photos of myself," says Banks. "They're like, 'Whoa.' But I tell them the truth. I want every girl to find their own beauty."
The America's Next Top Model executive producer remembers the moment when she knew she wanted to do more to help young girls, which was during her book tour for Tyra's Beauty Inside and Out.
"There was a girl with a black eye," she recalls. "And she said, 'How do I cover my black eye? My boyfriend hit me and I need to know how to cover it.' I will never forget it. I knew I had to go further and do more," says Banks.
It's a feeling she tapped into to partner with the Lower Eastside Girls Center for Community in New York and launch an ongoing TZONE Foundation program.
"I never want to be someone to just check a box and not show up," says Banks, who is hosting the second annual TZONE Foundation Flawsome Ball on May 6 at Cipriani Wall Street in New York City. "I want to be a part of this."
"Flaws are awesome – so, 'flawsome!' I love making up a word."
For more of our interview with Tyra Banks, pick up this week's issue of PEOPLE, on newsstands Friday