The actress, 41, uploaded a light-hearted snap of herself backstage suffering ‘pre-show nerves’ as she stood over a bin in a jumper, her underwear and some boots.
Trolls attacked the mother of one’s image, saying they thought she was too thin.
One commenter said: “You look so unhealthy, eat” and another added the image was “alarming”.
They commented: “This is alarming! I feel this pic is a cry for help, I hope you get the help you need.”
After receiving the vile comments on her picture, Anna decided to take it down from her Instagram, just 15 minutes after she initially uploaded the post.
One of the first people to jump to her defence was her estranged husband, Chris Pratt.
The actor, 39, has reportedly offered his support to his ex-wife.
According to Hollywood Life, a source explained: “Chris still has so much respect for a woman that he was so in love with for a long time and not only that the mother of his child,” a source told HollywoodLife. “His respect for Anna goes a very long way and that will never change and that is why he is heartbroken that people are body shaming her.”
“It’s awful, he hates it and he wants her to know that she has his support through all of this because he doesn’t want the bullying to continue or win. His hope is that she knows that there are so many people who care for her and respect her and he hopes that she doesn’t take the bullying to heart because she doesn’t deserve it one bit.’
Chris and Anna split in August last year after eight years of marriage.
The couple, who met in 2007 while filming the romantic comedy Take Me Home Tonight, but said attempts to save their relationship had failed.
The pair have remained friends for the sake of their son Jack.
Since their break-up, Chris has started dating Arnold Schwarzenegger’s daughter, Katherine while Anna has got close to cinematographer Michael Barrett.
Earlier in the week, Anna had opened up about dropping her six-year-old son off at kindergarten for the first time.
“Here’s the thing, I feel really guilty that I wasn’t more anxious,” the actress said. “Because it feels like all the other parents were very anxious and the kindergarten teachers are like, ‘Ah, is everything going to be OK?’ And I felt like…can’t we just drop him off?”
“Chris and I walked him there and we were trying to not transfer any, you know, hint of anxiety, not that I was having it.
“He just ran in and he was like, ‘Bye guys!’ But it was that funny mom guilt feeling of like, I feel like this should emotionally tug at me more than it is.”