Outside, on a warm morning in March, students at the University of the West of England are shading their faces with textbooks, legs rippling in the sun. Inside, in a cramped, bright room lined with ring binders labelled "Intimacy", the women who make up the world's only Centre for Appearance Research (Car) are talking quietly about perfection. I arrived here after following a trail of newspaper reports – on the effect of airbrushing in the media, on men's growing anxiety about their weight – reports used variously by politicians and educators to highlight the way our world is collapsing. It's here, with their biscuits and gentle, resigned chatter, that a team led by Professor Nichola Rumsey and Dr Diana Harcourt is compiling the research required to understand how we deal with changing attitudes to appearance, and along the way helping answer the question: why do we hate the way we look?

Two years ago I started writing a column for this magazine, illustrated by a photo of my face. At times it made me feel odd (I have never liked photos), at other times sad, often anxious. It made me more aware that I don't like the way I look, but more, I don't like the fact that I don't like it. But it's not just me. All Car's research suggests that Britain's body image is in crisis.

Body image is a subjective experience of appearance. It's an accumulation of a lifetime's associations, neuroses and desires, projected on to our upper arms, our thighs. At five, children begin to understand other people's judgement of them. At seven they're beginning to show body dissatisfaction. As adults 90% of British women feel body-image anxiety. And it doesn't wane – many women in their 80s are still anxious about the way their bodies look which, Professor Rumsey explains, can even affect their treatment in hospital, when their health choices are influenced by aesthetics. Many young women say they are too self-aware to exercise; many say they drink to feel comfortable with the way they look; 50% of girls smoke to suppress their appetite – is it too strong to suggest that these things, these anxieties, are slowly killing them?

Liberal Democrat MP Jo Swinson (who has succeeded in pulling a number of L'Oréal ad campaigns for being unrealistic) is one of a growing group of people whose campaigning indicates that it's something worth worrying about. Last year I attended every session of her government inquiry into body image, the results of which were published in a report this month. She cited research showing how current "airbrushing" culture leads to huge self-esteem problems – half of all 16- to 21-year-old women would consider cosmetic surgery and in the past 15 years eating disorders have doubled. Young people, she said, don't perform actively in class when they're not feeling confident about their appearance.

It is research backed up by a new documentary by Jennifer Siebel Newsom, Miss Representation, about the under-representation of women in positions of power – women who are high "self objectifiers" have low political power. They're less likely to run in politics, and less likely to vote: if value lies in their imperfect bodies, they feel disempowered. The long-term effects, the piling on of pressures one by one, like a dangerous Jenga tower, means women's – and increasingly men's, 69% of whom "often" wish they looked like someone else – lives are being damaged, not by the way they look but by the way they feel about the way they look. It's complicated.

Even researching such a thing is tricky. The truth feels slippery. "Why," I asked the psychotherapist Susie Orbach (who, since publishing Fat is a Feminist Issue in 1978, has become a loud and public voice in the conversation about body image), "when I know that beauty is subjective, that nothing terrible would happen if I put on weight, when my desk is covered in annotated research on bodies, do I still feel bad about the way I look?"

"Because none of us lives in a vacuum," she said. Simply acknowledging the pressure doesn't eliminate it. "We don't even know we hate our bodies because we take that for granted." She sighed. "When I wrote FiFi there was a pretty bad situation," she said, "but the women of my generation have given birth to… this." To my generation – 60% of whom feel ashamed of how they look. But before anybody begins to deal with this, this crippling western-worldwide anxiety, it's important to try and work out why. How did we get here?

At the Centre for Appearance Research, they discuss with me how invested people have become in their appearance. And how central it now is to the value they place on themselves. We've always compared ourselves to other people, but what has changed is the way we use images. There's a famous study which looked at teenage girls in Fiji after television was introduced to the island for the first time in 1995. After three years with TV, the girls who watched it the most were 50% more likely to describe themselves as "too fat"; 29% scored highly on a test of eating-disorder risk. One girl said of the western women she watched on Beverly Hills 90210: "In order to be like them, I have to work on myself, exercising, and my eating habits should change."

Today the web ensures that we are drowning in visuals: we're no longer comparing ourselves to "local images" – our friends – instead we're comparing ourselves to social-networked strangers, celebrities, and to Photoshopped images, of which we see around 5,000 a week. I always bristle a little when "airbrushing" or Photoshop is blamed for the rise of body-image anxiety. It seems too simple. While I was impressed by Jo Swinson's campaign to ban airbrushing in advertising, I did cheer, a little, when I read Tina Fey's thoughts: "Photoshop itself is not evil," she wrote. "Just like Italian salad dressing is not inherently evil, until you rub it all over a desperate young actress and stick her on the cover of Maxim, pretending to pull her panties down. Give it up. Retouching is here to stay. Technology doesn't move backward. No society has ever deindustrialised."

The problem is not the Photoshopping itself – the problem is that Photoshopped images threaten to replace all others, and that in slicing off the rounded hip of an actress it reveals our difficult relationship with the female body. The problem is that, in their ubiquity, Photoshopped images have changed our standards of comparison. So that's one reason. Images. I started to make a list.

The "size zero" debate that began a few years ago led to an angry dissection of the fashion industry's preference for skinny models. In response, a circular argument was repeated, laying blame on fashion magazines (for printing the pictures), then model agencies (for hiring the models), then designers (for making samples that only fit the very thinnest of them). In this month's Vogue, editor Alexandra Shulman launched the Health Initiative, a six-point pact between the editors of the 19 international editions, aimed at encouraging a healthier approach to body image within the industry. They promise to encourage designers to "consider the consequences of unrealistically small sample sizes of their clothing, which… encourages the use of extremely thin models". Is this the industry taking responsibility for our broken body image, for its power? Acknowledging that they help sell not only clothes, but ideas of which bodies are acceptable?

"We're not taking responsibility for it," Shulman says firmly. "We're saying we realise we're in a powerful position and we can do something about it."

We're sitting in her bright white office, beside shelves displaying international Vogue covers. She points at them one by one. "There's Kate Moss in Versace. That [sample-sized] dress is tiny. You can see it's pretty tight on her. Then there's Scarlett Johansson in vintage Prada – you see, 'real people', actors as opposed to models, don't fit sample-size clothes."

Caryn Franklin, Erin O'Connor and Debra Bourne, whose All Walks Beyond the Catwalk initiative encourages diversity in fashion, talk to designers and students about creating more "inclusive" designs. "The fashion industry has changed in the past decade," Franklin explains slowly, trying to put her finger on why our body image is in crisis. "The catwalk used to be a factory space. But digital changed everything – it's now become a luxury positioning experience, a consumer space."

It's helpful for fashion buyers (the audience at catwalk shows) to see clothes on a shape that is as close to a clothes hanger as possible – hence the tall, bony models whose breasts will not bother the line of a shirt. But since catwalk imagery has gone mainstream, these model shapes have drifted into the public subconscious. "We're helping the industry understand this," adds Franklin. "This inconvenient truth."

Shulman has been pushing for larger sample sizes since 2009, when she wrote a letter to major international designers complaining that their tiny designs were forcing editors to shoot them on models with "no breasts or hips". Has she seen any change? "Hmm. There is still a bit of a… blindness. I think fashion is a bit out of step with this. They don't realise that people would really like to see something different." She's right – Ben Barry (a PhD student at Cambridge University) surveyed 3,000 women, the vast majority of whom "significantly increase purchase intentions when they see a model that reflects their age, size and race".

Shulman was invited to give evidence at Jo Swinson's inquiry but turned her down. "I'm very anti-legislation, anti-government initiatives. I don't think they need to get involved. God knows they've got enough to be thinking about without worrying about sample sizes. And it isn't just about 'common sense'."

I'm learning this. I ask her about other myths – are there any commonly held beliefs about Vogue, the industry and body image? Her eyes fall on the magazine shelf. "Ah! I know one!" she says, leaning in. "We shot Adele for our October cover, and everyone said: 'How typical of Vogue – they shoot Adele and only show a head shot.'" It's true – bloggers were disgusted that they hid her size-16 body.

"But Adele would not let us pull the camera back," Shulman explains. "As soon as any of her body was shown on the camera's digital screen she'd say no. It was her desire to have a head shot, which I found very frustrating. I was desperate for a full-length picture." That issue was one of the worst-selling in Vogue's history.

I remember Orbach explaining that none of us lives in a vacuum. "Vogue," Shulman continues, "is one of very few [women's interest] magazines that never publishes diets, never points out when someone's put on weight. We don't come from that unhelpful culture where you forensically examine the way a woman looks. That's appalling. We don't have to put our hands up about that."

Are today's diets – the way we are encouraged to eat cognitively – to blame for our anxiety? An eating-disorder specialist at the inquiry confirmed that the "Atkins diet generates many cases for my work", but the problem is not eating disorders but disordered eating. Disordered eating includes competitive dieting and eating in secret – it can lead to both eating disorders and obesity, but more commonly just adds to the eater's anxiety.

Rates of depression in women and girls doubled between 2000 and 2010; the more women self-objectify, the more likely they are to be depressed. Could the mainstream media's warm embrace of disordered eating have contributed to that rise? Grazia reports that Beyoncé lost 60lb of "baby weight" by eating only lettuce. Cosmopolitan wrote about Kate Middleton's "Dukan diet", which begins with seven days of pure protein, and later two "celebration meals" a week. If women don't look like Beyoncé or Kate Middleton, their flat stomachs a testament to their stamina then, it seems, they are not working hard enough.

One celebrity whose body is frequently scrutinised (and scorned) by the tabloid media is The Only Way is Essex's reality star Lauren Goodger. "Never heard of Spanx, Lauren? Miss Goodger shows off muffin top in very unflattering dress," read one Mail Online headline. There are 546. "Oops, maybe you should've tried the next size up. Lauren Goodger's tiny dress feels the strain." "Haven't you learned your lesson? Lauren Goodger steps out in ANOTHER pair of unflattering leggings." Rather than the corrosive dripping-tap effect of reading these once a day over the last two years, read together these 546 headlines feel like quiet waterboarding.

I meet Goodger at Max Clifford's office. She is weeks into a "drastic diet plan". Many women feel judged on their appearance in some way, but what does it feel like to have those verdicts read by 99 million people a month? "It is quite… draining," she says. "I can't look at comments. I can't buy the mags any more. I used to love them, but I was happy then. Then my weight became a story, not just for the show but for the press. Yeah, I'm definitely aware of the online scrutiny. My body becomes my work." She thinks for a bit. "But just because someone's not a size 10 it doesn't mean she's a bad person."

Last year Goodger had a nose job because, she said, she'd hated seeing her profile on TV. Most of her female Towie cast members have had cosmetic surgery – mainly breast implants, a bum lift, Botox, lip fillers. "Where does it come from, the idea that natural is not beautiful, that we all need the model look?" Goodger asks herself. In response to Jo Swinson's inquiry, the British Association of Aesthetic Plastic Surgeons (Baaps) has called for a ban on adverts for cosmetic surgery, highlighting promotions that play on vulnerabilities, such as "divorce feelgood" packages of breast augmentation and liposuction, and surgical procedures sold via online discount sites such as Groupon.

"Do you think there should be psychological screening for those seeking surgery?" I ask Goodger tentatively. "It's a subject that's hard to talk about," she says. "Especially because I'm… within it."

We talk about the idea of "naughty" food, about the different expectations for men and women, about the celebrities who say they're "big and happy" then suddenly lose weight. There's a pause.

"My little sister was anorexic at 11," she says suddenly. "It started with someone at school calling her Miss Piggy. I mean, I didn't even know about dieting until I was 18. Things have changed so much. She gets the mags, she wants the bags, the Prada shoes. It's crazy. She's a baby! She wears lashes, make-up. But you do what everyone else is doing – you compare yourself. She's fine now, a year and a half later. But she'll message me going: 'Have you lost weight? You look really good' and I'll think: God, don't say that."

Goodger and I were both born in the 80s. In our lifetime (one that has seen the internet enter our homes, along with hundreds more television channels), expectations of beauty have changed enormously. What must it be like growing up today, when cosmetic surgery is advertised on public transport, when "baby-weight loss" diets are rife?

I gather together a group of under-20-year-olds at Livity, Brixton's "youth engagement agency", to talk about body image. It's not a concept that needs explaining to them. Apart from Stephen (who says: "The fact that I don't have an opinion on body image probably says something itself. Boys have it easier, definitely"), they have much to say.

First, some fictions they are keen to shatter. The pressure, the girls agree, is not, in fact, to be skinny – instead it's to look sexy. "Hot." "Everyone wants to look like Kim Kardashian, even though we know she's a boring person – we don't want to have her personality, just her body," says Claudia. "Not Kate Moss's. Curves, not bones."

This is the first time sex has been discussed – until now, everybody has talked about thinness and control, rather than changing your body to attract a boy. But as Bridget points out, you can starve yourself bony: "The sexy body is much more unattainable." "I think our generation is really savvy about the media," says Amber as they move quickly on to the subject of airbrushed ads. "So you know an image has been manipulated, but I suppose… you don't know what that's doing to you."

I wonder about the fact that these young people are so literate in the issues of body image (as opposed to simply "bodies") that their thoughts on the subject are so close to the surface. "We're forced to think about it!" says Bridget. "It's on every channel, every night. Programmes like Supersize vs Superskinny, or How to Look Good Naked, or freaky ones like Half Ton Mum, or A Year to Save My Life." Everyone shouts out names – programmes about overhauling your body with diets, clothes or surgery. "They have mixed messages," says Amber. "On one hand they're saying 'love your body', then on the other 'fat's bad, the worst thing you could do is be obese'. The message 'be healthy and do exercise' is a bit different from 'be happy in your skin', isn't it?" The rhetoric of empowerment, here, actually disempowers.

Do we hate our bodies because of reality makeover TV? Susie Orbach describes how they often provide "dysmorphic and distressed women" the opportunity to "compete over their body distress and win the prize of radical restructuring". The earliest technologies of body enhancement utilised techniques used on Second World War burn victims. "To hear [winning reality show contestants] tell it," Orbach says, "they've been through their own individual wars, too… Their compulsion to change their bodies is a result of a different kind of assault on women, and increasingly men, which is sufficiently damaging to have persuaded them that the bodies they live in are urgently in need of transformation."

Both the cosmetic surgery and the cosmeceutical industries (anti-ageing products) are growing, fast. It's these industries, "along with the fashion houses, the diet companies, the food conglomerates [which own the diet companies], the exercise and fitness industry, and the pharmaceutical and cosmetic surgery industries", that Orbach is now combating, because, she says, "they combine, perhaps inadvertently, to create a climate in which girls and women come to feel that their bodies are not OK".

Orbach debated with representatives from the diet industry in parliament to applause from the public gallery – outside women protested with placards saying: "Riot, don't diet." Discussing Weight Watchers' recent £15m TV ad, she suggested it was affordable to them only because their members are locked into lifelong "straitjackets" of unrealistic weight-loss expectations. When I speak to her later, she goes further. "I do think we should be prosecuting the diet industry for false advertising," she says firmly. If dieting worked, she argues, you'd only have to do it once. There is evidence that diets may in fact contribute to fat storage and that, in giving a sense that food is "dangerous", create conditions for rebellion, which eventually makes people fatter than they were to start with.

When I began my research, all roads led back to Orbach. She's been crucial in hammering home the dangers of body-image anxiety, yet figures show that we are feeling worse about our bodies than ever. "You have to make the argument that this isn't trivial, then you have to make the argument that this is a substantial issue, then you have to combat the industries. I'm exhausted by it," she says, throwing her head back. "But what other options do we have?"

She's working on a psychoanalytic research project on the transmission of body image from mothers to daughters, and she's pushing for interventions by midwives, trained to show new mothers how their own body-image dissatisfaction will affect their babies. "New mums are caught up in problems with their own bodies when they're bringing a new body into the world. We need a counterpoint to the nonsense that you should have a pre-pregnancy body six weeks after having a baby, or ever. What's the erasure about? That's where it should start." She takes a breath. "And teachers – it's all very well them taking classes about body image, but if they don't raise their own awareness about their own distress, then they're just passing it on."

Back at the Centre for Appearance Research, we make our way down the narrow university corridors for lunch. In this surprise heat, the café is full of academics fanning themselves with menus, the odd bare-legged man. I am feeling a bit hopeless. All the statistics about sadness; all the people, like me, who aren't able to enjoy their own health, privilege, relative youth, because of this niggle. This feeling that we don't look right.

Jo Swinson's report detailed various recommendations being put to government, regulators, voluntary organisations and the private sector. In light of Orbach's evidence, they call for a review of the "inaccurate" body mass index as the standard way of determining whether somebody is overweight, and for better support for new mothers. They ask advertisers to reflect "consumer desire for authenticity and diversity", and for tougher regulation of the cosmetic surgery industry. But all the people I interviewed balanced their delight at the inquiry with a healthy wodge of cynicism at how much change these recommendations would effect.

And I wonder what we can do – us lot, the people with the faces we don't like, with the cankles, the muffin tops, the limp, lifeless hair. It's in the personal, day-to-day things, I think. Like consuming media critically. The media is a construction – this is no secret. Magazines, film, TV, newspapers – they all rely on advertising. So reminding ourselves that the body types we see represented are the body types that generate purchases. Asking ourselves: "Am I being sold something here?" It's not a terrible thing, being sold to, it's just a… thing. Unpicking the media we consume, and talking about it, will help us feel better eventually. Cognitive dissonance programmes in schools have been effective – encouraging young people to speak out against the unrealistic ideals of beauty they see. In talking about it we reduce the internalisation of beauty ideals, and feel less awful about our implied failings.

I tell Car's Dr Phillippa Diedrichs about something Amber mentioned – about femininity and dieting.

"Eating becomes a means of communication," Diedrichs says after lunch. "In our food choices we're demonstrating our femininity." But it goes further than that. "We're socialised to be negative about our bodies," she says, and a slideshow of moments flashes through my head. Women standing in the ladies' loos complaining about their boobs. Or comparing their limbs to their colleagues' unfavourably. She introduces me to the idea of "fat talk", everyday conversation that reinforces the "thin ideal" and contributes to our dissatisfaction. Like: "You look great – have you lost weight?" Or, on being offered a bun: "Ooh, I really shouldn't." "After three minutes of fat talk," says Diedrichs, "there's evidence that our body dissatisfaction increases significantly." Naming this – fat talk – makes much sense to me.

After a day at Car, my body-image anxiety hasn't disappeared, but I can at least see a way to control it. We hate how we look because of our new, complicated visual culture, because of a fashion industry that has not adapted, a media that forensically analyses women's bodies and saturates our culture with body-change stories. Because of the rise of cognitive eating, the increasing abilities and accessibility of cosmetic surgery. Because to be feminine, today, means to hate your body.

I leave their building feeling quite different from when I arrived. I have the same legs, the same face, the same teeth, but something in my mind has changed.