She shared a workout video on Instagram to show part of a routine she's using to change her body shape for the film.

It shows the actress lifting weights as part of a bodybuilding programme with her personal trainer.

Hathaway, 35, added that she originally wanted the video to be set to Queen's Fat Bottomed Girls.

She wrote: "I am gaining weight for a movie role and it is going well. To all the people who are going to fat shame me in the upcoming months, it's not me, it's you. Peace xx.

"PS I wanted to set this to Queen's Fat Bottomed Girls but copyright said no. Continued peace xx."

Whilst The Devil Wears Prada star has not revealed what the weight transformation is for, she does have a number of projects that could be behind the weight gain.

This includes Live Fast Die Hot, a drama about a New Yorker's whose life changes when she becomes a mum and The Lifeboat, a story about a young woman on trial for murder.

Hathaway's next major film to be released is Ocean's Eight, where she is alongside a number of leading actresses including Cate Blanchett, Dakota Fanning, Sandra Bullock and Rihanna.

Who else has changed shape for a role?

Renee Zellweger gained two stone for Bridget Jones' Diary
 

Jennifer Lawrence played an ex-ballerina in Red Sparrow and says losing weight made her feel hungry all the time.

She told Vanity Fair: "I remember having a meltdown, freaking out that I had eaten five banana chips."

One of the most memorable transformations was Renee Zellweger in Bridget Jones' Diary.

The actress gained over two stone in weight by eating burgers, milkshakes and chocolate bars.

Christian Bale transformed himself for The Machinist
 

Perhaps the biggest shape shifter in Hollywood is Christian Bale.

His emaciated appearance in The Machinist is a far cry from how he looked in American Hustle.

For the former he ate an apple and a can of tuna a day to lose weight, whilst his diet for the latter included doughnuts and cheeseburgers.

Another actor who has both lost and gained weight is Matthew McConaughey.

He lost just under three stone to play HIV-positive Ron Woodruff in Dallas Buyers Club.

McConaughey then underwent another transformation for the film Gold, gaining weight through a diet of cheeseburgers and beer.