Speaking to Us Weekly, the daughter of former Alaska Governor Sarah said that having "corrective jaw surgery" in December of last year changed the shape of her face.
"It's not plastic surgery," Bristol declared.
She went on to add: "It improved the way I look, but this surgery was necessary for medical reasons... so my jaw and teeth could properly realign... I don't obsess over my face."
Aside from the medical nature of the procedure, Bristol admitted that she's "thrilled" that one of the side-effects was a more mature physical appearance.
"I look older, more mature, and don't have as much of a chubby little baby face," the star remarked.
It was reported yesterday that Palin will star in a newly-announced reality series with fellow former Dancing with the Stars contestant Kyle Massey and his brother Christopher for cable channel BIO.
> Palin slams '50-year-old bully' Griffin
Watch a comparison of Bristol Palin's pre and post-surgery appearance below: