"It's not everyday I like to show a lot of skin but these days I'm feeling confidant," the former Clarissa Explains It All star captioned the pic. "Thanks Nutrisystem! Look for my new commercial that begins airing April 21!"
The 37-year-old star, a spokeswoman for Nutrisystem, first flaunted her 40-pound weight loss in February, just two months after she told Us Weekly that she was "so sick of things not fitting properly" after her third pregnancy.
Hart and her husband Mark Wilkerson have three children -- Mason, 8, Braydon, 5, and Tucker, 19 months. She currently stars in the ABC family series, Melissa & Joey.
[Melissa Joan Hart]
Celebrity Breakups and divorces of 2014 [PHOTOS]