There’s a trope in horror films that I’m really sick of: the use of older women’s bodies as a tool of disgust. In It Chapter 2, a naked older woman scurries through a kitchen, meant to evoke terror. In Midsommar, an older woman appears among a group of naked younger women during unsettling cult rituals, designed to underscore the bizarre nature of the scene rather than any allure. In The Visit, a young boy is horrified to encounter a naked older woman wandering the hallways at night, exclaiming, “Jesus, I’m blind.”

In each case, the portrayal of these women’s bodies and actions is framed as inherently grotesque; their ageing skin and perceived lack of desirability render them monstrous. What should be a natural aspect of life is depicted as unnatural. Older women, typically rendered invisible, are put on display and, through a misogynistic male lens, presented as hideous. Look at their untaut skin, the lens demands. Look at their unperky breasts. Look at how unf*ckable they are.

And as we know, if a woman is unf*ckable, she is unworthy. She can either be invisible or an object of disgust and derision.

The image of older women’s bodies in horror contrasts with the way we are usually shown female nudity in the genre – or any other genre. In horror, young, slim, conventionally attractive women are a staple, and these women’s bodies are sexualised, even in violence. If running from someone, their top will come off. If being tortured by someone, their bodies will writhe. If being killed, their final screams will be orgasmic.

While young attractive women in horror are likely to be the victim, older women – in a moral judgement – are more likely to be the villain. Older women aren’t just less f*ckable, they’re less moral, less good, and less desirable to society at large. Wouldn’t it be better, this trope implies, if women simply disappeared after the age of thirty-five, and stop inflicting their unf*ckable bodies and selves onto the world?

This is the question explicitly stated by the men in Coralie Fargeat’s audacious new body horror, The Substance. In a role that references her own struggles with having her age and appearance decimated by the media throughout her career, Demi Moore plays Elisabeth Sparkle, a Hollywood actress-turned aerobics workout host.

She is breathtakingly beautiful – but she’s over fifty, which according to Dennis Quaid’s slimy network manager, makes her irrelevant. Overhearing plans to fire her, Elisabeth fears fading into obscurity. She takes some desperate measures in the form of The Substance, a neon-green, injectable body enhancement programme, delivered to her with syringes and clear instructions – or is it a warning? “The two of you are one,” the packaging reminds her.

Elisabeth dutifully injects herself with the mystery substance – and if that seems far-fetched, ask women who have had filler or Botox to explain what exactly is in their face. We’re told to just trust things that will make us look younger all the time. After the injection, in a scene of visceral body horror that will leave you cringing, Elisabeth essentially births another self from her body.

This version is younger, tauter, slimmer: perfect. The young replacement, named Sue (Maragaret Qualley), can go out and rule the world, while Elisabeth’s body lies in a form of comatose hibernation – for a week. Then they must switch. Sue can go become the network’s new star, but has to revert power back to Elisabeth every seven days.

It should be simple enough – but Elisabeth’s self-loathing and jealousy of Sue results in her simply staying inside all week, mourning her lost youth, while Sue – her fame in the ascendancy – wants more time, more power, and starts overstaying her week. But remember the Substance’s warning; they are one. For Sue to get more time, she has to take some of Elisabeth’s bodily fluid as fuel, which comes with a cost.

Elisabeth’s body parts begin to age rapidly. First, a finger becomes gnarled and sun-spotted. A calf becomes riddled with building varicose veins. Each time, Elisabeth considers stopping the programme, filled with deep self-loathing about her ageing body. But if she ends Sue, then what is she? Just an aged-out actress with some now prematurely wrinkled appendages? Sue may be Elisabeth’s only reason to go on.

But Sue’s hunger for validation won’t be contained. And the impact to both of their bodies will be unimaginable. Moore and Qualley are both mesmerising, with Moore capturing Elisabeth’s descent into catatonic, then manic self-loathing. Qualley meanwhile brings a steely ruthlessness to Sue, who smiles and simpers at male executives who want her to be a virginal sex symbol, but doesn’t flinch while siphoning fluid from Elisabeth’s lifeless body. Sue is a parasite to Elisabeth’s host, literally draining the life-force out of her – but the disdain she has for Elisabeth merely reflects Elisabeth’s feelings about herself.

The rivalry between Elisabeth and Sue has echoes of Showgirls, and there’s a camp, late eighties flair to the styling which is all neon spandex and coiffed hair. This bold, brash, garish aesthetic is fully embraced by Fargeaut, who plays with the trashy, hyperbolic flair of the network’s workout videos, with relentless focus on the body.

An early scene where Dennis Quaid eats shrimp while patronising Elisabeth is hot in extreme close-up, showing every mangled piece of crustacean flesh and fleck of saliva. The camera of Sue’s workout show Pump It Up lingers on her ass, and even when alone, Sue poses as if always being watched – a nod to the male gaze of cinema, which constantly turns female characters into sexualised objects.

And the body horror is wonderfully, outrageously grotesque, with grisly violence and an audacious final act that is monstrous and hilarious in equal measure. The film is easily 15 minutes too long, and tighter editing could have made it feel sharper. But its exploration of ageism, misogyny and how our culture promotes self-loathing in women is impactful, unapologetic and visionary.

Body horror can often be entertainment, or shocking, but rarely comes with such a clear vision and philosophy. An exhilarating, cathartic, terrible beauty.