For a phenomenon that has such visible results, there is huge secrecy around weight-loss drugs.

Ellen lied to get her Wegovy pen. “I put weights around my neck under my dressing gown when I got on the scales,” she said. “They do the review and five ­minutes later, I got the approval.”

Like most of the hundreds of thousands of people in the UK who have taken weight-loss drugs in the past few years, Ellen went to an online pharmacy to pay her ­prescription. “You have to film it live – here’s my passport, here’s my body, here I am getting on the scales,” she said.

At 5ft 9in (1.75m) and 12 and a half stone (79kg), Ellen – not her real name – was barely ­overweight. The hidden weights and a ­sudden height loss – “I said I was 5ft 2in” – were enough to get a prescription.

“I was on it for six months and I’ve lost three stone,” she said. “I’m a touch lighter than I should be, but the plan was always to come down a bit more, to go up a bit.”

It’s not what Wegovy or Mounjaro were designed for – which was to help seriously obese people – nor Ozempic or Rybelsus, drugs to help diabetics manage their disease. All four are types of semaglutide, which mimics the hormone released by the body when eating food, GLP-1 . The essential effect is to make people lose their appetites.

But they offer hope to those who had despaired of ever being able to lose weight, and to ­politicians ­grappling with the problems of an obesity epidemic: more than a ­quarter of adults in England are ­living with obesity and nearly two-thirds of those aged 18 or over are overweight at least.

It’s still not clear whether these injectable medications will be wonder drugs that are central to solving the obesity crisis, or sticking plasters – a temporary fix, with users simply regaining lost weight after they stop taking them.

But there are already signs, three years after Wegovy began to be used in the US and barely a year since it was officially launched in the UK, that semaglutide medications are ­changing the world – and ­changing it in ­unexpected ways.

Fashion leads

The waif is back. At Berlin ­fashion week in July, Namilia sent a model on to the catwalk wearing an “I heart Ozempic” T-shirt, ­pushing into the open a ­conversation that had been going on behind the scenes: models taking Ozempic to be thinner.

“You do get naturally thin 16- or 17-year-old girls who are sucked into the industry then told ‘if you want to stay in it, you’ve got to starve’ – it’s a really abusive grooming space,” said Caryn Franklin, the former BBC Clothes Show presenter who is now a fashion and identity commentator.

A campaign that she set up with supermodel Erin O’Connor, All Walks Beyond The Catwalk, seemed to have worked – in 2017, major ­fashion houses signed up to a charter to protect models by ­banning size zero, and plus-size models started to become visible at fashion shows.

“But now we seem to be going back to thin models,” Franklin said. “It feels like representation of ­average women was just a trend.”

Fashion editors have complained about the new wave sweeping the catwalk and those watching it. In the past few weeks, Chioma Nnadi of British Vogue described the “new cult of thinness” as ­“troubling”. Anna Murphy of the Times said she was sad and angry at “the ­erasure of women”, while Jo Ellison of the Financial Times said she was depressed at fashion’s “dangerously rail-thin aesthetic”. “We’re really beginning to see this kind of ­cultural effect of Ozempic take place,” Ellison said on the podcast Life and Art from FT Weekend.

Hollywood follows

Fashion is the fastest culture vehicle, a taste leader, Franklin said. “Stylists who style starlets for the red carpet will go straight to a fashion house to get a sample garment,” she said. “So then she’s under pressure to fit it – the garments are designed and women have to fit in them. It’s the wrong way round.”

Weight-loss drugs were “just another way of helping women destroy themselves through eating disorders,” she said.

That pressure applies to ­established stars too, trying to keep their place in Hollywood’s ­pantheon or on TV screens, particularly in the US where Ozempic has been taken off-label – prescribed legally for a purpose for which it was not approved – since it was advertised in 2018. A few have spoken ­publicly about taking the medications, such as Rebel Wilson, Kelly Clarkson and Amy Schumer, as well as older celebrities including Oprah Winfrey, Elon Musk, Stephen Fry, Whoopi Goldberg and Kathy Bates, who has been keen to point out that most of her weight loss was from diet and exercise.

But there is still plenty of secrecy in the image-dominated ­industries, and plenty of speculation by fans who have a new have-they-haven’t-they game to play on Reddit or Instagram about people in the ­spotlight, instead of gossiping about plastic surgery or Botox.

Social lives

As demand for weight-loss drugs has trickled down, some of the social impacts are starting to become clearer.

“People are secretive because they’re ashamed of using this tool to do it,” said Juls Abernethy, a women’s wellness coach, therapist and cofounder of the Body Retreat, who has worked with several women looking for extra help to lose weight.

None of them were prepared to tell their family or friends what they were doing. One hid her injectable pen among the condiments in her fridge so her husband wouldn’t find it. People who feel ashamed of being fat, as if it were a moral failing, feel the same about using medication – of the fear of being seen to cheat, Abernethy said.

“We talk about weight loss like a war,” she said. “Banish the bulge and fight the fat. It’s supposed to be ­difficult. It’s supposed to be ­arduous. And now you can pick up a pen for £150 or something.”

Ellen was more open about her methods. She shared her Wegovy pen with her husband, adjusting her dose to reduce the side effects of intense nausea that came when she did eat food.

She told her friends in London, but stopped discussing it with other people because it became difficult to deal with accusations that she was causing problems for diabetics (there were shortages of Ozempic for Type 2 diabetes ­sufferers last year) or with endless questions about what it was like to inject ­herself in her midriff once a week.

“Our whole life used to be planned around food,” she said. “But we stopped eating out because we’d just order a starter, and it felt a bit cheap. Then we went to New York for a week and realised when we got there we’d made no dinner reservations.”

The “food noise” – thoughts about when to eat and what to eat – simply disappeared, she said. During the six months she took Wegovy, the ­couple “saved an absolute ­fortune on food”, she said. “We’d get a Domino’s ­delivered and two pizzas would last us three days. And, sadder for me, it really puts you off alcohol.”

Weight-loss industry

Abernethy is one of the few people still advertising weight-loss retreats, she said. “Most people have changed their name or dropped the weight-loss element,” she said. “You don’t know why people aren’t clicking, but over the course of this year, we’ve definitely seen a downturn in our weight-loss retreat, which is ­generally our most popular. You can’t ignore the Ozempic thing.”

For larger firms, it’s a bigger problem. Sima Sistani stood down last month as chief executive of WW International, which owns WeightWatchers, after trying to turn around the company’s fortunes.

Its shares have fallen by 97% since 2021, even though it now offers a “GLP-1 programme” and offers semaglutide as part of its WeightWatchers Clinic business.

Food industry

“Let’s not get ahead of ­ourselves – 4.1m people are eligible to receive Wegovy,” said Alfie Slade, government affairs lead at the Obesity Heath Alliance. “At the moment, we have capacity to treat 35,000 people a year on the NHS in specialist weight management clinics. The source of obesity is the broken food ­environment where companies have a financial incentive to sell the most profitable products, ones that are high in fat, salt and sugar.”

In 1983, grab bags and multipacks didn’t exist, McDonald’s had 1,000 outlets and KFC had a few hundred. There are now 48,000 fast food ­outlets in England alone, and bans on junk food advertising have yet to come into effect.

In the US, which has had longer to see the effects of weight-loss drugs emerging, companies that make and sell ultra-processed foods are identifying potential problems. Research by JP Morgan suggests that ­people on GLP-1 drugs spend up to 17% less on food in the first six months, and Walmart said last year it was already seeing people buy less food, prompting investors to sell shares in PepsiCo and Mondelēz.

Nestlé has responded by launching a line called Vital Pursuit – ­frozen pizza, pasta and sandwiches that it bills as a “companion for GLP-1 weight loss medication users”.

Gyms

“Though most of the weight loss is body fat, a downside of calorie deficit is that some of the weight lost is muscle,” said Prof Lora Heisler, chair in human nutrition, Rowett Institute, University of Aberdeen.

Gyms have responded by ­replacing treadmills and other ­cardio machines, previously seen as the best way to shed pounds, with more weight machines and free weights.

There has been a longer-term shift towards people trying to gain muscle mass, which depletes as we age. But there is also “intense ­interest now in finding ways to block muscle loss during weight loss”, Heisler added, with researchers looking for ­pharmaceutical solutions too.

Eli Lilly is working on ­bimagrumab, which she said “has shown some ­success in ­preclinical trials in ­protecting ­muscle from being lost” while ­people take GLP-1 drugs.

Nutrition is a wider issue for users of the drugs.

Ruchi Bhuwania Lohia, founder of Wellness with Ruchi, said: “When ­people come in, they can be quite nutrient deficient. They lose water, then muscle mass.”

Economic effects

Perhaps the least expected impact of the rise of semaglutide was on the share price of airlines. Analysts ­predicted that lighter passengers would save fuel costs, with United Airlines saving $80m if average ­passenger weights fell by 4.5kg.

Denmark is another beneficiary. Novo Nordisk, which makes Wegovy and Ozempic, was estimated last year to be worth more than Denmark’s annual GDP and the Danish government publishes figures with and without its new behemoth.

Even publishers have felt an Ozempic effect. In the US, print sales in the “health and fitness” category have fallen by 15% ­compared to 4% overall, ­according to Circana. In the UK, fitness and diet books were down by 14% in 2023, compared with a 2% fall across the market, according to Nielsen BookData.

Matthew Bell, a director at Frontier Economics, said obesity cost Britain about £100bn per year in lower quality of life for those ­living with it and higher costs to the NHS. But discovering what ­proportion of people lose weight and keep it off would be important for ­understanding the real economic consequences of GLP-1 drugs, rather than the anecdotal evidence that has emerged so far.

“You can use that data to ­understand the impact on different economic variables – ­employment rates, productivity, purchasing ­habits,” he said.

It remains to be seen whether weight-loss drugs will have the same impact as other ­technologies, such as smartphones or ­washing machines.

Statins, which help avoid hardening or narrowing of the ­arteries, have had an ­economic impact by preventing ­countless deaths from heart attacks and strokes.

“Those drugs had knock-on effects,” Bell said. “People have a higher quality of life for longer, but towards the end of their life they may have more complex needs. And when large numbers of people live longer, that has impacts on pensions and a range of other economic decisions, including retirement ages.”

Medical research

A lot of medical research ­funding has focused on the outcomes of ­obesity, according to Naveed Sattar, professor of ­cardio­metabolic ­medicine at the University of Glasgow and chair of the government’s obesity healthcare goals programme. Obesity is associated with ­diabetes, kidney disease, heart ­failure, heart attacks and strokes, as well as sleep apnoea, fatty liver ­disease and even skin conditions.

“We’ve been slow to shift our ­priorities to look at weight and interventions,” Sattar said. “People have come up with some very clever technologies to tackle diseases. But if we just use common sense and help people lose weight or stop them putting on weight, they wouldn’t need that device.”

Researchers have been trying to work out how to reduce sleep apnoea, where the weight of the tongue causes it to collapse and occlude breathing. Some sufferers need machines at night to help them breathe, and researchers are trying to find ways to burn away fat cells in the tongue. Yet losing weight may be a simpler solution.

It could be bad news for CFOs at some medical firms which have built their businesses treating those diseases. Cardiovascular disease has created a market worth $250bn (£192bn), and analysts suggested this could shrink by 10% by 2050.

Side effects

Ellen’s loss of interest in alcohol as a result of taking Wegovy is backed up by research. A study from Loyola University in Chicago, published last week in Addiction, showed patients with addictions to alcohol or heroin who had been prescribed Ozempic were less likely to be hospitalised.

Dr Riccardo De Giorgi from the University of Oxford’s Medical Sciences Division, said trials ­investigating smoking are under way and there may be a positive effect for people with dementia.

“I would normally be quite careful and sceptical but one of the reasons why we have grounds to be optimistic is that we do see nice matching between what we see clinically and what we are seeing in pre-clinical and mechanistic studies,” he said.

There are also indications that it may reduce the risk of heart ­problems, with the MHRA, the UK regulator, approving ­semaglutide for prevention of heart attacks and strokes in July after studies ­suggested it may reduce the risk of death by 20%. And researchers are examining the drugs’ effects on ­fertility. Women who have previously struggled to have children say they have become pregnant after taking semaglutide for weight loss, leading to a host of #OzempicBabies posts on social media.

But scientists have urged women not to take GLP-1 drugs in case there is any undiscovered risk caused by the drug, as happened with thalidomide.

Semaglutide has proved divisive among those following the body positivity movement, a response to the aggression or prejudice directed at fat people. When Gabi Menard, a body positive influencer ­popular on TikTok and Instagram, revealed that she had been taking Ozempic, she experienced a ­backlash from her fans.

Mental health

For Juls Abernethy, there are deeper questions to address about weight loss and destructive eating habits.

“When I started working with one client, all her anxieties around comfort eating, eating on her own, started to come out [after starting to use weight-loss drugs] . She had no appetite, so she started skin ­picking, around her fingers. Her cuticles were raw, she’d cause a scab and then she’d pick at that.

“For me, as her therapist, that was her general anxiety ­manifesting itself in a way that used to ­channelled into food.”

Ellen is stopping her use of Wegovy, and said feeling hungry felt “weird”.

“I’m a girl – you’re on a diet your whole life,” she said. “You always feel you’re missing out, you’re ­sacrificing something. But when you’re taking it, you don’t even think about eating. You don’t feel like you’re missing out. Suddenly, the sacrifice is back and I’m sad to stop being like that. It’s dangerous.”