Demi Lovato Demi Lovato

Demi Lovato flaunted her bod in a figure-hugging dress at the MTV Video Music Awards Sunday, but not everyone had nice things to say about her new curves.

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After critics taunted her weight gain on Twitter, the 19-year-old quickly fired back to the haters. "I've gained weight. Get over it," she tweeted. "That's what happens when you get out of treatment for AN EATING DISORDER."Lovato later deleted the tweet and wrote: "Guess what, I'm healthy and happy, and if you're hating on my weight you obviously aren't. :) #UNBROKEN" (Unbroken is the name of her new album, which hits stores Sept. 20.)

Demi Lovato: I will deal with my eating disorder for the rest of my life

Lovato completed a three-month stint for "physical and emotional issues" in January and later revealed that she has had a lifelong struggle with an eating disorder and bipolar disorder.