This week, 20-year-old actor Chloë Grace Moretz said she had been “body-shamed” by a male actor on set when she was 15. He was her co-star at the time, in his 20s, cast in the role of her love interest, and he said he would never date her in real life, because she was too big. It was a comment that drove her to tears. Moretz is the latest in a string of Hollywood stars who are prepared to be more open about their experiences of sexism in the industry, from Jennifer Lawrence to Emma Watson. Like the late Carrie Fisher, who revealed she was asked to lose weight before appearing in the new Star Wars series, Moretz touches on something particularly troubling: the pressure on women on screen to maintain a body size that may be unrealistic or unhealthy.

Unfortunately, this is nothing new. Silent-film expert Pamela Hutchinson cites the example of Greta Garbo. “Louis B Mayer hired her for MGM in 1925, when she was already a success in Europe, with the caveat that ‘In America, we don’t like fat women’. Garbo ate nothing but spinach for three weeks and then dieted, rigorously, for the rest of her Hollywood career.” There were even more extreme measures. “An actor called Molly O’Day had her excess weight cut away by a surgeon. In 1929, Photoplay magazine explicitly blamed the death of comic actor Katherine Grant on the Hal Roach studio’s demands for her to lose weight.”

Carrie Fisher, who said she was told to lose weight before appearing in the new Star Wars films. Photograph: Chris Pizzello/AP

The issue has persisted ever since. Emma Thompson recently said she threatened to quit the 2008 film Brideshead Revisited after a female co-star was asked to lose weight. “I said to them, ‘If you speak to her about this again, on any level, I will leave this picture. You are never to do that.’” Troublingly, Thompson feels the problem is increasing. “It’s evil what’s happening,” she continued, “and what’s going on there, and it’s getting worse.”

While male actors may be asked to lose weight for extreme roles – such as Matthew McConaughey playing an Aids patient in Dallas Buyers Club – women are routinely asked to slim down simply to play female leads. I’ve heard of women on set being openly poked and prodded by male studio executives who discuss their unsuitable size – and these actors are tiny in the first place. Jennifer Lawrence has spoken of being considered “plus size” or “fat” in Hollywood, while on Twitter, Amanda Seyfried said she had been considered “overweight”. X-Men: Apocalypse actor Sophie Turner also chimed in recently. “There are often times when I have done jobs and they’ve told me that I have to lose weight, even when it has nothing to do with the character,” she told Porter magazine. “It is so fucked up.”

This infuriating pressure prompts the question: why? If this is about idealism and adulation, are audiences really asking for this? Actors such as Christina Hendricks and Sofia Vergara, who are curvier than the Hollywood average, have no shortage of admirers.

The feminist campaigner Laura Bates, who started her career as an actor, says this pressure is “absolutely rife, both in and outside Hollywood”. The pressures on Hollywood women lead to a screen ideal which then heaps more pressure on ordinary women and girls. “That Moretz was just 15 when this happened,” says Bates, “also highlights how body-shaming can impact girls from an incredibly young age. We know that girls are just five when they first start to worry about their size and shape, and that a devastating one-quarter of seven-year-old girls has dieted to lose weight. They are also bombarded with airbrushed, unrealistic media and advertising images that repeatedly send them the message that their bodies are not good enough, that they will be judged by their looks, and that they must conform to a narrow, media-mandated notion of ‘beauty’.”

Joan Smith, human rights campaigner and author of Misogynies, agrees. “Making girls and women feel uncomfortable about their bodies is a way of attacking their confidence. It makes women defensive and inward-looking, and when you feel like that, you lose your sense of having a place in the world. It happens in Hollywood because the stakes – money, fame – are so high, but it goes far beyond that. At a time when we have a legal right to equality, it’s a way of restoring the old inequality – women are permanently open to scrutiny. It’s not always conscious but it’s nasty and effective.”

Bates also points out the “massive double standards” in Hollywood, saying “women are often more pressurised than men.” Women who aren’t “Hollywood thin” are very rarely cast in mainstream thrillers, sci-fi or fantasy films, and in dramas they usually appear in “character” roles, often played by older actors. When bigger female characters are the lead in a film, their weight is never incidental, but rather a defining characteristic, such as the role played by Gabourey Sidibe in the 2009 film Precious. Meanwhile, male leads come in all shapes and sizes – Jack Black, Seth Rogen and Jonah Hill (now slimmed down) have all appeared frequently in a variety of leading roles, including drama as well as comedy, and stars such as John Travolta, Russell Crowe and Vince Vaughn have been allowed to change physically over the course of their careers.

Gabourey Sidibe, star of 2009 film Precious. Photograph: Robyn Beck/AFP/Getty Images

Comedy seems more welcoming of female actors such as Melissa McCarthy, though many of her lead roles have been in films made by her own production company, and others such as Rebel Wilson are usually relegated to the funny best friend role. Amy Schumer has something resembling an average body shape – watching 2015’s Trainwreck, I remember being startled to see someone who looked more like me and my friends on the big screen. I thought, perhaps, this signalled a cultural shift, but since then I’ve mostly been reviewing romcoms with stick-thin heroines – perhaps the kind that Moretz’s cruel co-star was comparing her with. And sadly, his kind of “body shaming” isn’t confined to Hollywood – far from it.

Actor, comedian and writer Arabella Weir thinks Moretz should name and shame the man in question. “The ‘problems’, as expressed by this particular guy,” she says, “are all his, not hers and her BMI. To allow comments about one’s size to cause one pain is to validate them. Name, shame and circulate as widely as possible all comments of this nature and let their authors attempt to justify them – they’re in the wrong, the subject never is. Until women refuse to be categorised by their size, and that includes naming the person, then we’ll always be seen as participating somehow in the myth that thin equals good.”

There is hope on the Hollywood horizon: the Sundance hit Patti Cake$ (out on 1 September) is a joyous celebration of a female rapper (Danielle Macdonald) that shows her character suffering from body shaming while she challenges expectations of what a performer should look like. While the story tackles the subject of her weight, it’s as much about her character and her career aspirations. Moretz herself is in an upcoming body-positive take on Snow White, although she spoke out after its poster seemed to body-shame her character. Also in animation, last year’s Disney teen Moana had a more realistic shape – and this is in a genre previously well known for its preposterous female figures.

But animation is one thing, living, breathing actors another. “Hollywood has the power to change things by showcasing a far greater diversity of women’s body types, shapes and skin colours, rather than reinforcing suffocating stereotypes and impossible standards,” says Bates. “It has an opportunity to be part of the solution rather than part of the problem.”

She’s right. We need more female actors to speak out – and for Hollywood to listen.