The 21-year-old singer now thinks "every body type is beautiful", reported In Touch Weekly.
"I think it's good to have someone with a regular average body on the pop charts. It's about loving what you got and rocking it," the 'All About That Bass' hitmaker said.
Recalling her struggle as a high school girl, Trainor said, "It was pretty serious. I would sit in class feeling uncomfortable. I regret a lot of those moments and those thoughts that I had in my head," she said.