“I am gaining weight for a movie role and it is going well,” Hathaway captioned her post, which included a video of her workout. “To all the people who are going to fat shame me in the upcoming months, it’s not me, it’s you. Peace xx.”
She also added a cheeky note that she wanted to set her workout video to the Queen song “Fat Bottomed Girls” — “but copyright said no,” she explained.
In the video, Hathaway runs through an intense-looking routine of bench presses, ab work, push-ups and more.
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Hathaway is mom to son Jonathan, 2, and has previously spoken out about body image, as well as the unnecessary pressure on new mothers to lose baby weight.
“There is no shame in gaining weight during pregnancy (or ever). There is no shame if it takes longer than you think it will to lose the weight (if you want to lose it at all). There is no shame in finally breaking down and making your own jean shorts because last summer’s are just too dang short for this summer’s thighs,” she wrote on Instagram in August 2016. “Bodies change. Bodies grow. Bodies shrink. It’s all love (don’t let anyone tell you otherwise.).”
And after posting that body-positive message, Hathaway spoke to PEOPLE about learning to appreciate her new, post-baby shape.
“I think shape is an ongoing thing in everybody’s life,” she said in September 2016. “I’m not trying to recapture something that was. I’m going with what it is now.”
“Some things I guess are the same as they were, and other things are a little bit different. I’m just so proud of what the changes signify,” she continued. “So, there’s no rush to do anything. I’m so happy being here.”