updated 05/01/2014 AT 5:00 PM ET
•originally published 05/05/2014 AT 8:30 AM ET
Tyra Banks is not one to keep her self-doubt a secret.
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.”