When Branneisha Cooper was overweight, she felt both invisible and like she stood out.

Her friends would get attention when they were out together, while she was overlooked. But she also had a sense that everyone was staring at her, scrutinising her.

Everyday scenarios were daunting: fairground rides (would she fit in the seat?), working out (would it hurt?), clothes shopping (would she find attractive clothing in her size?).

At the end of 2022, Branneisha, now 28 and working in Texas for a major retailer, began using weight-loss injection Mounjaro. She’s lost about six stone (38kg).

Things changed quickly. Suddenly, she could exercise without her body getting sore, colleagues made more small talk with her and she felt comfortable going on adventurous dates with her boyfriend. She was go-karting, dancing and going to arcades – activities that previously made her feel self-conscious.

But despite feeling like she had a “second chance at life”, weight loss was bittersweet.

“It was almost like I had stepped into a different world overnight,” Branneisha recalls. “People were suddenly more friendly, more attentive, and I was given opportunities and respect that didn’t exist before.”

“That rapid shift was jarring and really opened my eyes to just how deeply size bias is ingrained in our culture,” she continues. “Psychologically, it was a lot to process because while I was the same person, the way I was perceived had completely changed.”

Weight-loss transformations are nothing new. In the 90s and 00s, they filled the pages of tabloid newspapers, sold celebrity diet regimes and inspired popular TV series like The Biggest Loser, You Are What You Eat and Celebrity Fit Club.

But in the 2020s, the advent of weight-loss injections like semaglutide and tirzepatide (marketed under brand names Ozempic, Wegovy and Mounjaro) has meant people can lose huge amounts of weight rapidly, without undergoing invasive surgery. The jabs suppress people’s appetites, causing them to feel fuller sooner.

Wegovy has been available on the NHS in England, Wales and Scotland since September 2023 with strict eligibility criteria, but weight-loss drugs are expected to become more accessible when Mounjaro becomes available through NHS England later this year.

The jabs, which are not suitable for everyone and can have severe side effects, are also available from pharmacies in the UK for people who can’t get them prescribed by their GPs.

So other than the physical difference, how does the way you’re perceived change when you lose weight quickly and look different to the world?

People who have used the injections have told BBC News that rapid weight loss has caused a massive shift in the way they are treated – by both strangers and loved ones – as well as a change in how they approach their lives.

Branneisha’s feeling of sticking out and being overlooked at the same time while overweight is one others can relate to.

When you’re overweight, people either avoid eye contact or “really stare and glare at you”, says Jess Phillips, 29, a primary school teacher from Sittingbourne, Kent.

She previously felt uncomfortable taking flights, travelling on public transport and eating at restaurants. Finding suitable seating worried her, as well as the feeling she was “taking other people’s space”.

People had even shouted “fat” at her from cars and at a festival.

A trip in 2023 to Sorrento, on the Italian coast, was a major catalyst for starting weight-loss injections last June.

“Everyone was staring at me the whole time,” she says. “They’re just not used to people being that big out there.”

Since losing weight, Jess has noticed a big difference in how she’s treated in public.

“Strangers seem to be a lot more chatty with me than they ever were before,” she explains.

She feels “more invisible in a nice way”, she continues. “I don’t feel like people are looking at me when I go to different places. I feel nicely anonymous… I’m not standing out in any particular way.”

This is something that Jeannine A Gailey, sociology professor at Texas Christian University, explored in her 2014 book The Hyper(in)visible Fat Woman.

“My argument is that those who are marginalised, including fat people, become hyper-visible and hyper-invisible”, meaning they’re sometimes ignored and sometimes made into a “spectacle”, she tells the BBC.

Amy Toon, 34, a content creator from Solihull, felt this way. Before starting on the drugs, she shopped online “because of the overwhelming fear of people looking at me”, she says. “I just didn’t want to leave the house.”

Since losing weight, “people are a lot more smiley and just make eye contact,” she says. “I never had that before. It’s really strange and it’s also really sad at the same time.”

Society has preconceptions about how overweight people are expected to behave, and treats them accordingly, says Caleb Luna, an assistant professor at the University of California, Santa Barbara specialising in fat studies.

“Fat people are expected to hide and shrink ourselves and not be proud,” says Prof Luna.

Weight isn’t a protected characteristic in the UK or in most other parts of the world, meaning it isn’t illegal to discriminate based on size, except if the person’s weight is classed as a disability.

Academics say that anti-fat bias can have significant implications, from how people are perceived in job interviews to how doctors interact with them. People make “all kinds of personality assumptions” about other people based on their body size, according to Prof Luna.

“I don’t understand why there’s this rage that some people seem to feel upon looking at someone who’s overweight,” says Alix Harvey, a 35-year-old marine biologist from Plymouth who’s lost around three stone (20kg) after starting weight-loss injections last year. “It’s socially acceptable to hate fat people.”

Weight-loss drugs have helped people like Branneisha, Jess, Amy and Alix lose weight – but they’re not right for everyone. Some in the healthcare industry have concerns about the wrong people getting hold of the jabs – including those who are already a healthy weight or have a history of eating disorders.

Common side effects of semaglutide and tirzepatide include diarrhoea, nausea and vomiting, according to the National Institute for Health and Care Excellence (Nice). Rarer side effects include acute gallstone disease and pancreatitis, and the NHS warns that there is also a risk of hypoglycaemia, which happens when your blood sugar level drops too low.

Jonathan Pinkney, professor of endocrinology and diabetes at the University of Plymouth, says while there are “great expectations and hope around the drugs”, trials show people “do tend to relapse” after they stop taking them, meaning the weight loss isn’t sustained.

Alix says this worries her. “Am I going to be treated differently again? Because I like the way I’m currently being treated.”

Some people who take the medication say there’s stigma attached to using the drugs to lose weight, too, which Alix says puts some people off taking the injections.

“I didn’t expect the hatred,” she says, noting that some people see the use of weight-loss injections as “cheating” and a “socially unacceptable” way to lose weight.

“A lot of people see it as the lazy way out,” Amy says, referring to comments about weight-loss drugs left on her social media videos.

For sustained weight loss, the injections need to be used as part of a healthy lifestyle, including a balanced diet and regular exercise.

“People think that it’s a magic wand then it’s not,” Amy says. “It doesn’t just melt the fat away.”

“Even if you injected yourself once a week and a pound a week just evaporated from your body, what would that matter?” Alix says. “Why is that cheating?”

“You basically can’t win,” she says, referring to the stigma attached to both being overweight and using injections to lose weight.

People who’ve lost weight using the jabs tell the BBC their self-confidence has massively improved. Many say they feel much happier to take trains and planes. Some say they now wear brighter colours and tighter clothes. Others say they’re more vocal sharing their opinions at work.

Amy says she now feels comfortable taking her children swimming, while Jess says she’s been able to book her first-ever ski trip, something she’d never thought was possible before.

“I actually think it must be annoying how confident I am at the moment,” Jess laughs.

But many of the women we spoke to were left feeling sad for their previous selves, or frustrated at the unfairness of their past treatment.

“It’s so sad that your weight can define you,” Amy says. “I haven’t changed at all as a person. The only thing that has changed my appearance.”

Branneisha echoes these thoughts.

“It makes me sad when I have experiences that are different now because the larger me deserved that same attention and love,” Branneisha says. “Being smaller now makes me sad for my former self because people looked at me differently.”