The musician explained in the caption that posting an unedited bikini photograph of herself is her "biggest fear", having previously edited other pictures of herself "so that others think" she is "their idea of what beautiful is".
"I want this new chapter in my life to be about being authentic to who I am rather than trying to meet someone else's standards," Lovato wrote.
"So here's me, unashamed, unafraid and proud to own a body that has fought through so much and will continue to amaze me when I hopefully give birth one day."
Lovato added that it's a "great feeling" to have resumed her acting career on TV and film without the stress of following a "strenuous workout schedule before 14-hour days" or "crazy diet s***".
The Tell Me You Love Me singer concluded her message that while she is not "stoked" about the way she looks, she is "appreciative" of her body.
"And sometimes that's the best I can do," the 27-year-old wrote. "I hope to inspire someone to appreciate their body today too."
Several of Lovato's 73.5 million Instagram followers left praiseworthy comments underneath the star's empowering post.
"Showing us YOU is so incredibly beautiful. Thank you Demi! Love you mama!" wrote model Ashley Graham.
"And the truth will set you free! I love your transparency and boldness. Gorgeous Demi," commented American television personality Rosie Rivera.
Comedian Amy Schumer shared a screenshot of Lovato's post on her Instagram Story, writing in a caption that the singer is "the truth".
After posting the unedited bikini picture on her Instagram profile, Lovato shared an additional message on her Instagram story.
The singer wrote that while the photograph was "so hard" for her to share, she feels "blown away by the love and support" her fans have displayed towards her.
"Let's be the change we want to see!!!" Lovato added.
Earlier this year, Lovato responded to a body-shaming headline by stating that she is "more than" her weight.
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies