Prior to her days as a Sports Illustrated Swimsuit cover star, Olivia Culpo suffered from body image issues.

The model, 28, relentlessly compared herself to her older sister Aurora and felt that she was an “ugly duckling” when she was younger.

Culpo also struggled with her weight as a child. Her dad put her on a diet at age 10.

“Honestly growing up I felt really ugly which is a terrible thing to say," the former Miss Universe said in a joint interview with her sister Aurora on Monday.

SI SWIMSUIT MODELS OLIVIA CULPO, JASMINE SANDERS AND KATE BOCK SHARE 2020 COVER

Olivia Culpo reveals she struggled with her body image when she was a child. (Getty)

She told hosts of the “Emergency Contact” podcast that she was “really different looking” as a kid.

“My older sister looked like the Barbie doll. I was overweight. I had to look myself in the mirror and say, ‘Okay, you’re different,’ because I was," the model said.

Culpo and Aurora then recalled the time the now-model was put on a diet.

"Our dad is amazing but our dad is like, Type A and has run over a dozen marathons," the Sports Illustrated star began.

OLIVIA CULPO'S BOYFRIEND, CHRISTIAN MCCAFFREY, REACTS TO STAR'S SPORTS ILLUSTRATED SWIMSUIT COVER

Olivia Culpo's sister says she became confident after she was put on a diet at age 10. (Getty)

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She continued: "When I was 10 years old, yeah, I was put on those diets and I kind of realized, when you put in the work you get the results. It kind of all started from there."

Aurora said: "She knew that she was overweight, so I think that she developed a skill for situating herself in situations where she would get the most attention. And then she got hot and she had that skill. That’s how you get on Sports Illustrated."