Earlier this summer, the actress said she was "appalled and angry" about a billboard advert for her movie Red Shoes & the 7 Dwarfs, which suggested being overweight made you less beautiful.
And now, she's spoken for the first time about a time she was fat-shamed on set by one of her male co-stars.
She told Variety: "This guy that was my love interest was like, 'I'd never date you in real life,' and I was like, 'what?'. And he was like, 'yeah, you're too big for me' - as in my size.
"It was one of the only actors that ever made me cry on set."
Chloe didn't reveal who it was, but said the actor was in his mid 20s - while she was 15 at the time.
"I went bawling to my brother and he was like, 'what happened?'. And I was like, 'he told me I was too big'. My brother was so angry.
"I had to pick it up and go back on set and pretend he was a love interest, and it was really hard. It just makes you realise that there are some really bad people out there and for some reason, he felt the need to say that to me.
"You have to kind of forgive and not forget really, but it was just like wow. It was jarring. I look back on it and I was 15, which is really, really dark."
Chloe Grace Moretz isn't the first star to highlight the issue of body shaming.
From Kate Winslet and Jennifer Lawrence (pictured) to Meghan Trainor and Amy Schumer - more and more stars are refusing to feel guilty about their appearance.
"I heard my body is a topic of conversation so I wanted to say, I'm proud of my body and you should be proud of yours too," Lady Gaga said earlier this year.
Lena Dunham, meanwhile, has said: "I've accepted that my body is an ever changing organism, not a fixed entity - what goes up must come down and vice versa."
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The roundabout, which saw more than 80 collisions and 90 people injured in 2012-14, was replaced with two-way traffic on Sunday.
Transport for London (TfL) said congestion was due to "traffic getting used to the new layout".
"It's a very busy junction and it always will be," a spokesman said.
The reintroduction of two-way traffic at the junction for the first time in 50 years was a "key milestone" in the £25m transformation at Elephant and Castle, TfL said.
In addition to the new road layout, left turns from Newington Causeway towards New Kent Road and right turns from New Kent Road to Newington Causeway have also been banned.
But road users took to Twitter to complain about their Monday morning commute.
"It's 8am and the queue for the new #elephantandcastle junction starts somewhere south of Camberwell. allow extra 1hr 4 journey (or walk!)", a Twitter user posted.
"Shock horror! All approaches to Elephant and Castle worse than ever. Only TfL could spend millions and millions to make something worse!" tweeted @tango97.
Andy Woodward tweeted: "Delays around Elephant and Castle even worse today. If this was the tube there would be outcry. Commuters use buses too!"
Road users had been advised of traffic changes with a countdown to the traffic switch and advisors and police were on site to help keep traffic moving, the TfL spokesman said.
A spokesman for London TravelWatch said: "It's early days - we need to wait and see how it pans out."
TfL plans to convert the space created by removing the roundabout into a new public area.
It will replace subways with new pedestrian crossings, create new cycle routes and introduce a 20mph speed limit, TfL said.
Chloe Grace Moretz is not a fan of body shaming.
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The removal of the Elephant and Castle roundabout has been causing chaos for commuters, with motorists complaining of queues of more than an hour.