"One of my biggest dreams, having collected Barbies since I was a kid, is to have my own Barbie BUT with my actual body type.. Weight & height," she tweeted, encouraging her followers to help her make her birthday dream a reality.
"Lovatics! Blow up @BarbieStyle to make it happen!" she continued. "That would be one dope 21st birthday! Hahaha. Also, Barbie should make dolls with cellulite! After all, around 95% of ALL women have it!"
Lovato, 20, has been vocal about her body image issues and eating disorders in the past, admitting to U.K.'s Company magazine that she had to deal with lots of "emotional and physical issues" when she checked into rehab for three months in 2010.
The X Factor judge has since revealed that she was admitted to the treatment center in order to deal with her struggles with bulimia, cutting, and bipolar disorder -- problems she's had from an early age.
In a recent interview with Rolling Stone, Lovato recalled having to battle her own demons as a 7-year-old actress on the set of Barney & Friends.
"The principal called my parents and made me sign this suicide contract saying that I would not kill myself," she recalled. "They weren't expecting that so young."
Post-treatment, Lovato said her mom and stepdad were instrumental in helping her feel comfortable about sharing her struggles with others. "My parents were like, 'You have two choices. We can either just shut it down and not talk about it, or you can tell people what's up,'" she said. "There was no hesitation, really. I opened up that gate."