When Meghan Trainor was 12, "some dude" told her that he'd "rip out his car radio" if her songs were ever played.

Wonder if he followed through on that? Trainor's body image anthem "All About That Bass" is blowing up the charts as it's being spun coast-to-coast on Top 40 radio. "It's such a cool feeling," the 20-year-old tells ET's Rocsi Diaz.

ET was with Trainor in Nashville as she prepares to unveil her Title EP, due out September 9.

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Trainor opened up about the whirlwind surrounding her debut hit, being bullied and embracing her body.

"I grew up a chubby girl. I had two brothers," she said. "My parents loved us, they just fed us whatever we wanted."

Trainor recalled one particularly heartbreaking exchange in her younger years.

"I did have this one boy come up to me, who, like I loved him, I was so in love, And he told me, 'You'd be like real hot if you were 10 pounds lighter,'" she said. "I was like, 'Ugh, that's it! I am going to cry all day and not eat for the rest of the day.'"

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But the singer is quick to clarify that she never battled an eating disorder.

"I wasn't strong enough to have an eating disorder," she said. "I tried to go anorexic for a good three hours. I ate ice and celery, but that’s not even anorexic. And I quit. I was like, 'Ma, can you make me a sandwich? Like, immediately.'"

Trainor also said that she felt particularly touched by many young girls suffering with eating disorders who have reached out to her. "I'm glad a lot of the comments I've gotten are about [girls'] eating disorders and how my song saved them – which is crazy, but amazing."

It wasn't all heavy conversation during ET's sit-down: Diaz also got to watch Trainor perform an acoustic version of "All About That Bass" on the ukulele… and it's amazing. Check that out in the video below.

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