Trainor says she only just began writing for her Title follow-up this week, but she already has "a good chunk of songs," including one called "Curves," and she even gave us a sneak peek of the lyrics.
"'I got curves and I know how to use them, I got curves with no plans to lose them,'" she teased. "'Cause I love who I am, so are you the man' -- I'm talking to the boy -- 'the man who can handle my curves?' That's the chorus."
The message fits perfectly with Trainor's new #OwnYourCurves campaign with FullBeauty.com, in which she challenges curvy girls: "Why just wear it, when you can own it?"
"[FullBeauty] loved the message with the 'Bass,'" Trainor says of how the partnership came together. "It's hard growing up, especially for young curvy girls like me. I remember shopping at the mall and all my friends would be the small, and I would be getting that L."
Trainor looked flawless during our interview in a figure-hugging black dress -- complete with lace detailing -- and a black-and-white blazer. While the 21-year-old admitted that she's new to the fashion scene, she couldn't help but gush over the ensemble.
"I feel like a dope businesswoman, but also sexy," she said. "Everyone can't stop complimenting me today!"
One of Trainor's favorite looks of her career came fairly recently, in the music video for her new Peanuts soundtrack song, "Better When I'm Dancing."
Wearing a gorgeous red, long-sleeved dress, Trainor busted a move with a handful of extras including her friends, family members, and her dad, Gary, who all flew in to Los Angeles from her hometown of Nantucket for the shoot. (Dad’s in the blue shirt at the end of the video!)
"He's a soulful, funky dude," she said of her father, who inspired another new song titled "Dance Like Your Daddy." "We had a pool growing up and he would put out disco balls everywhere and he would throw these funky pool parties with bubble machines -- the whole thing -- and we just play Earth Wind & Fire. That was the best part of my childhood.
"I remember one night I went all out," she continues. "I did not care what the adults thought, I just danced my heart away. He inspired me."
We could be hearing both "Curves" and "Dance Like Your Daddy" ("It's dope," she says of the track) on Trainor's upcoming sophomore LP, though it's too soon to speculate on a release date. Trainor did reveal that she is back in the studio with producer/songwriter Kevin Kadish, with whom she worked on "Bass," "Dear Future Husband," and "Lips Are Movin'." "We're doing big things," she says of the new collaborations. "I'm really excited."
In the meantime, Trainor is up for multiple honors at the American Music Awards next month including Artist of the Year. She'll face off against stars like Taylor Swift, Ariana Grande and Nicki Minaj in the category.
"It's still in shock," she says of the nominations. "I still just signed up! I still just got here! And I thought, especially because of surgery, I've been gone, I've been home chilling. I figured [with] the award shows -- I'm not even gonna go to this year. But I'm there, I'm nominated. I'm gonna perform, hopefully."
Fingers crossed for a new performance! In the meantime, take a look back at Trainor's first-ever interview with ET and see what moment brought her to tears in the video below.