The press briefing for October’s Clinical Cosmetic Reconstructive Expo in London was delayed – there had been another death. A cluster of journalists gathered on the mezzanine while below them visitors filtered past signs for She Lase and Zero Gravity Skin and a stand for a company called Eurosilicone that claims to have been “Empowering women for over 30 years”. At the far end of the conference hall, a woman was having her jawline enhanced with fillers in front of a rapt crowd; the Safety in Beauty stand was empty.

Back on the mezzanine, there was a rustle of suits as the British Association of Aesthetic Plastic Surgeons (BAAPS) entered the room. Apologies for the delay, one said solemnly, there has been another death. A second British woman has died this year after a Brazilian Butt Lift (BBL). Which made their announcement that they were henceforth warning surgeons not to perform the procedure particularly urgent. The brief was called “The Bottom Line”.

Bottoms are big business in 2018. For a generation whose mothers spent mornings trying to shrink their thighs in front of Jane Fonda videos, today there is no such thing as a bum that’s too big. The perfect body has changed every decade over the past century, stretching and curving over time like a time-lapse sand dune.

Body parts have come in and out of fashion depending on the mainstream obsessions of the moment, from the lean boyish chests of flappers in the 1920s, signifying liberation from corsetry, through 30s bosoms and 40s legs, to the sexualised femininity of Marilyn Monroe’s hourglass figure, and on eventually to 80s muscles (Power! Strength!), and 90s, well, bones. Extreme slenderness was maintained beyond the millennium, but with added breasts, a modified Monroe, minus the tummy.

‘The bigger your butt is the more attention you get’: Jennifer Lopez, pictured above with Tom Cruise. Photograph: Matt Sayles/AP

In 2010, breast augmentation procedures in the UK increased by 10% to 9,418, remaining the most popular cosmetic surgery procedure. And then came the arse.

“Big bums are now associated with women with attitude and a sway who are non-white, which is desired,” says Susie Orbach, the psychotherapist who has been analysing women’s relationships to their bodies for more than 40 years.

In 2012, I spoke to a group of 20-year-olds about the media pressure to change their bodies. Rather than extreme thinness, they said the pressure was to look sexy. “Everyone wants to look like Kim Kardashian, not Kate Moss. Curves, not bones.” Which sounded like a positive development, a move away from disordered eating and dangerous attempts at control, until they pointed out that it also requires a tiny waist. You can starve yourself bony, but “the sexy body is much more unattainable”.

In 2014, the focus turned to the bottom. Butt lift injections and buttock implants were the fastest-growing plastic surgery in the US, up 58% from 2012. The French sociologist Jean-Claude Kaufmann cited economic reasons. “In uncertain times, people look for security,” he said. “Men are attracted to women’s hips and the buttocks for security and reassurance. Women respond to this. It’s deeply psychological.” Or, from Jennifer Lopez: “The bigger your butt is the more attention you get.” In 2015, the American Society of Plastic Surgery dubbed 2015 another “year of the rear”.

And then came the deaths, 33 of them in the US following complications from BBLs in the last five years.

Today, the aesthetic ideals of pornography have seeped into the mainstream. If a woman isn’t built with a big bum, exercise might reshape it, but there’s no diet that can create it, hence the booming business in surgery and cosmetic procedures, as well as entry-level purchases, such as firming creams and “butt lift” leggings. At an average cost of £3,000 abroad and £8,000 in the UK, the BBL uses liposuction to extract fat from a patient’s thighs to then inject it into their buttocks, but less invasive treatments proliferate. Nearly 320,000 buttock augmentation or buttock lift procedures were performed globally in 2015, according to the International Society of Aesthetic and Cosmetic Surgery, a 30% increase in the number of procedures since 2014.

Shape test: Jane Fonda works out in 1979. Photograph: Reed Saxon/AP

“My generation are 100% more interested in the shape of our bottoms, rather than our boobs,” 24-year-old Beth Cobb told a newspaper, explaining her investment in weekly bum-lift procedures using a roller that emits microcurrents of electricity. “It’s probably because we see a lot more celebs showing them off on Instagram. Now we have the technology, we can make our bodies change to fit the trends, not just change what we wear.”

Instagram, that seductive hellmouth where women holiday in their lunchbreaks, contributes to the growth of bums in a number of ways. There are the celebrities, yes, sharing their “belfies”. There is the fetishisation of the bodies of black and Latina women. Kim Kardashian’s 2014 naked shoot by Jean-Paul Goude for Paper magazine, arguably the launchpad for the body trend that is today called “thicc”, was inspired by Goude’s (who is white) 1976 portrait of Carolina Beaumont, who is black; the portrait was published in his book Jungle Fever.

The big butt trend is sold as a step towards greater body acceptance

In 2014, American Vogue declared the big bum on trend... for white women: as soon as a trend goes mainstream, women of colour are eliminated from the story. “So common is the process, it has its own Twitter hashtag,” wrote Yomi Adegoke. “#Columbising – when, like Christopher Columbus, white people think they have discovered something that was already in existence.” There is that. There is also the rise of “body positivity”, of women sharing pictures of curves they’d been taught were shameful. And there is Instagram as a platform for cosmetic surgeons to advertise directly at women who, tipsy on the combination of insecurity and images of arses as empowerment, will click through to adjust their own.

The latest post from Elite Aftercare, a clinic in Turkey (home of medical tourism) is a headless portrait of a happy customer, photographed from the front and from behind and tagged #BBL, #choices and #mybody. Scroll through to September, and there’s an update about a post-mortem on another of its patients, Leah Cambridge. She was a mother of three from Leeds, who, following this procedure, died on the operating table in August.

At the Expo’s press briefing, the BAAPS doctors discussed a study analysing one London hospital where, since 2013, they’d seen a six-fold rise in cases needing urgent follow-up care from procedures done abroad. Complications from BBLs ranged from severe bacterial infections to tissue dying, scarring, wound ruptures and abscesses. One patient had a “flesh-eating” infection. BBLs have the highest death rate (conservatively, 1 in 3,000 operations) of all cosmetic surgery procedures, due to the risk of injecting fat into large veins that can travel to the heart or brain. In August, a celebrity Brazilian cosmetic surgeon, Instagram name Dr Bumbum, was charged with murdering one of his patients. Dr Denis Furtado had performed an operation on Lilian Calixto to enlarge her buttocks in his own flat. He had nearly 650,000 followers.

Screen idol: Marilyn Monroe’s hour-glass figure made her a sex symbol in the 1950s. Photograph: Imaginechina/REX/Shutterstock

“A vulnerable group of patients are openly being targeted through social media,” said outgoing BAAPS president Simon Withey, “to travel abroad for cheaper cosmetic surgery – and this trend is likely to rise.” On Instagram, foreign clinics offer British customers “mummy makeovers”, and deals where the flight is free if you buy multiple operations – everywhere they promise that clients will feel “empowered”.

Their glamorous imagery is in stark contrast to the photos accompanying an NHS report on the wall at the Expo, about the complications of cosmetic surgery abroad, one of which shows a buttock abscess being drained. “Hot!” choked a security guard, walking by.

It’s not just cosmetic surgeons who claim they can empower women. For those who felt their bodies had been dismissed and sneered at for decades, but now find their arses the height of fashion, the big butt trend has been sold by the body positive movement as a step towards a more diverse body acceptance. But… can body trends ever be a good thing? “The move towards bigger bums isn’t a good thing,” says Orbach, “It’s a thing. What may at first seem to mirror some women’s previously excluded experience simultaneously excludes other women, which would be OK if commerce weren’t riding on it and suggesting that big bums are the solution.”

While fatalities are the most headline-grabbing result of Britain’s new pursuit of the bigger bottom, the implications of a changing obsession are less shocking, and more depressing. A realisation. Women will never be comfortable in their bodies, because the goal posts of what is acceptable keep shifting. We are encouraged to remain constantly at war with ourselves, shrinking, growing and utilising all the evolving technology that claims to alleviate the same anxiety that, simply by existing, it continues to feed us. And, to do so – to try and create your own Kardashian butt – is a rational reaction in 2018. The alternative is to be irrelevant, unbeautiful, and therefore, unseen.

“Bodies and the surface are not our only calling card,” Orbach adds. “We are not brands, but people who can contribute and challenge and dare to live from our unique bodies, not facsimile ones.”

Whew. All this from a bum. How did we get here? How did we get here from something that seemed so simple, so positive, so cheeky? A punchline, an inherently funny aspect of being human? An arse, we’re learning, is never just an arse. This is a trend we may need to sit on for a while.

The bottom line

The costs, risks and significant rise of the Brazilian Butt Lift

• A Brazilian Butt Lift, or BBL, is the colloquial term for buttock fat grafting, an elective cosmetic procedure which can cost up to £8,000 (in the UK) and involves removing fat from one part of the body via liposuction and transplanting it via injection into the buttocks, for a fuller effect.

• The British Association of Aesthetic Plastic Surgeons (BAAPS) said it was the most dangerous cosmetic procedure to undergo. Gerard Lambe, consultant plastic surgeon, explains: ‘It has the highest death rate of all procedures due to the risk of injecting fat into large veins in the buttocks, that can then travel to the heart or brain.’

• In the past five years, plastic surgeons have seen a 150% increase in the BBL business in the UK.

• In the US, the American Society for Aesthetic Plastic Surgery has tracked a 26% jump from 2016 to 2017, making BBLs the surgical procedure that has seen the second most significant increase in that period – 33 people in the US have died after the surgery in the past 5 years.

• About one in every 3,000 BBL patients worldwide has died of a pulmonary fat embolism. Twice as many developed chronic or serious complications.

• Nearly 320,000 BBL procedures were performed globally in 2015, according to the International Society of Aesthetic and Cosmetic Surgery, a 30% increase since 2014.