Julie Worboys, 49

Five years ago, Julie Worboys gave up her job as a warden for a sheltered housing estate to look after her husband, who is disabled. "It was quite an energetic job, but when I stopped I think that's when the extra weight went on," she says. She describes food as "like a comfort blanket" and you don't have to be a psychologist to see that the food she likes - cakes, sweets, chocolate - isn't just about the taste. When she was a child, both her parents worked long hours and her grandmother would look after her, giving her puddings and cakes. "To compensate for them working, my dad would bring me home a big bag of sweets on a Friday night. It was supposed to last me all week but it never did."

She has always been large, she says. "Obviously at school, I got all the usual comments. It makes it worse, because you're upset so you go home and eat. When I got married in 1980 I was a size 22. It just snowballed, and the more depressed I get about it, the more I eat." Buying her wedding dress was the last time she went clothes shopping with friends. "It does stop your life," she says. "If I go to a restaurant, which isn't often, I will always try to get in the corner. I can't go on holiday abroad because sitting in a plane seat is awful - getting the seatbelt on, putting the tray down. You have to ask for this extension belt that comes in bright orange and the air steward walks down the cabin with it - it's embarrassing. I love swimming but I won't go because I'm too self-conscious."

How does she feel about herself? "I've tried to laugh it off but you can't always," she says and her eyes well with tears. "I've tried everything. I can lose the weight but I can't keep it off. I can lose five stone, then I get bored and think one sweet or one cake won't hurt, and, of course, one leads to two, three and it all goes back on. Or a bill comes in, and I get down and then it's comfort eating. I've seen dieticians and they've told me what I should and shouldn't eat. Everyone talks about willpower, but I just haven't got it."

In the last year, Worboys, who lives in West Byfleet, Surrey, has put on three stone and now weighs 23st - "the heaviest I've ever been" - and it is starting to seriously affect her health. "My husband says I wake up fighting for breath in the night. I love walking down the Thames with the dogs, but I walk for 10 minutes and I can't do any more."

She says the GPs she has seen in the past have been unsympathetic. "They'll say, in not so many words, that you've got yourself into this situation." What does she think about the various proposals to treat Britain's growing obesity problem? Does it annoy her when politicians talk endlessly about it? "It does, when you think about how much money is spent on alcoholics, drug addicts. Smokers get their free patches. I know we're not being forced to eat food, but they're not being forced to drink alcohol, inject themselves with drugs or smoke. I think we should be treated the same. I don't want to tar us all with the same brush, but I think we should be treated as if we are addicts.'

Worboys has asked for stomach surgery. She had been thinking about it for a while, but decided after seeing the television presenter Fern Britton talk about it (in the fuss that surrounded the revelation of her surgery, Britton said she hadn't wanted to talk about it in case it encouraged other people to undergo such a serious operation). "Surgery isn't a lighthearted way of losing weight and I'm very aware that it is a big operation, but I could sit here and drop dead anyway of a heart attack, so I need to give myself a chance," says Worboys. "Now, it depends on whether I get the funding for it from the primary care trust."

Each operation costs the NHS around £10,000, although if you weigh this against the long-term cost of treating a patient for problems resulting from their obesity - diabetes drugs, knee and heart surgery, for instance - it doesn't seem a huge outlay (it is thought that the NHS spends £500m a year treating these secondary conditions, a figure that will rise). "If they say no, then I'll stay as I am, which to me is very sad. I'm asking for help and if I don't do anything about it now, I know I will die fat. I need to try to do something about it and have a little bit of a life left."

Ken Clare, 46

By the time Ken Clare was 40, he weighed 30 stone and, at his heaviest, he was 34 stone. He had been a large child, but the weight started piling on when he became a psychiatric nurse, and later a manager in the NHS, a stressful job that left him with little time. "So I ate junk food, takeaways," he says. "I would come home at night and use alcohol as a sedative." Food, he says, was inextricably linked with his emotional state. "I would eat when I was happy and I'd eat when I was sad."

Clare works at a hospital near Liverpool as a specialist nurse and counsellor for people about to undergo weight-loss surgery. He had a Roux-en-Y gastric bypass in 2002, which reduces the size of the stomach and attaches it directly to the small intestine, thereby reducing the amount of fat that can be absorbed. He had been on every diet going, and had taken obesity drugs, but none of it worked. Losing weight wasn't the issue, he says - keeping it off was. Surgery was a last resort, which he arrived at simply because he knew his weight would kill him. He has lost around 16st since the operation and he looks good for it. "You probably think I'm fat now, but I'm a shadow of my former self," he says. After his operation, he set up his online support group Weight Loss Surgery Information Forum (wlsinfo.org.uk), which has more than 10,000 members.

He is able to talk about his former life with humour and honesty, but the reality of daily life when you are obese sounds unpleasant. "You get lots of skin infections and irritations," he says. "It was embarrassing being a healthcare professional and getting knackered walking up the stairs, sweating. I would have to put pins in my shirts because I was always popping my buttons." He got a senior job in the NHS but failed the medical. "I went home and cried. I felt I couldn't tell people because I had got this job on my merits, except I was too fat to do it."

He was given a disabled parking badge because his mobility problems were so severe. Before, he would get to work two hours early just to get the nearest parking space to his office. "Sad that," he says. "I can remember certain milestones, like not being able to buy clothes in a normal shop and having to look for specialist shops. Shirts for big men tend to be very loud, which announce your presence. I would wear these Hawaiian shirts, burst in the room. I was always larger than life and people would say, 'You can really cope with being big, it doesn't bother you.' But inside, I was wrecked. As a bloke, you feel you can't tell anyone. There were times when I was the biggest person in the room at a conference. I couldn't walk because I was in pain - I was on crutches. You worry about breaking chairs. It starts limiting your life. If we were going out to a restaurant, I'd send my wife in first to check the chairs were OK and there was enough room to get through to the table. I stopped going to family occasions."

He talks about "obesophobia" as "the last bastion of prejudice. There are a lot of negative feelings about obesity I've come across on a personal level, and on a professional level too - a lot of doctors don't like fat people." Why didn't he just stop eating unhealthy food? "If I knew that, I'd sell the answer," says Clare. "There would be no more obesity." People don't appear to be talking about the psychological causes. "It is self-inflicted but, to me, it's a complex disease," says Clare. "I see a lot of parallels with alcohol and drug abuse. I think, for me, there was a big emotional component to eating and an addictive element." Clare was never offered counselling on the NHS, but has had cognitive therapy since his operation, which has helped. "Not everyone I work with is a food addict, and I wouldn't describe people as 'food addicts' because you can end up alienating some people, but I have an addictive personality."

Kirsty Powell, 19

Last year, a report by the Foresight thinktank recommended "fat camps" - basically boarding schools where overweight children could be sent to lose weight - to combat the increasing problem of childhood obesity. They are a controversial issue: critics say that fat camps stigmatise children, and the weight they lose usually always goes back on again. Kirsty Powell, who lives near Rossendale in Lancashire, says going to one has changed her life.

She weighed nearly 16st when she went to Wellspring in New York (there are similar camps in Britain, including one run by Wellspring in the Lake District, but Powell wanted to go to the US). She lost 3st in the eight weeks she was there last summer and since she has been back. "There was a strict schedule," she says. "You get up in the morning about 7.20am, then you do a 45-minute walk at 8am. Then we'd have free time, so we'd go on the internet, check Facebook, that sort of thing. Then we'd have breakfast - scrambled eggs and porridge, but they had all sorts. During the day we'd do sports or activities like dancing lessons or self-defence and fitness classes. We did adventure classes twice a week, where we would do canoeing. Twice a week, we would have group therapy. That was amazing. I was a bit apprehensive at first, but it was great. That, for me, was my biggest help. You are talking to girls who have come from all different backgrounds, but you talk and you've all got the same issues. You think, 'I'm not the only crazy person in the world.'"

Powell wasn't always overweight, but when she was 15 she became ill with glandular fever and never really got well again. "I was at home, bored, I was eating and I was too ill to exercise." When she was 17, she was diagnosed with ME. Her confidence was low, and putting on weight made it worse. "I had been on every diet," she says. "I was taking diet pills, tried to make myself throw up. I begged people to try and get me drugs like speed to try and lose weight. The GPs were no help. The first doctor I went to about my weight said I wasn't trying hard enough. He eventually referred me to a nutritionist, but the appointment wasn't for six months. It was downheartening, because I was trying."

Powell's parents paid around £5,500 for her to go to Wellspring, obviously beyond the means of most people. Powell believes that weight-loss camps for children and young adults do work, "but there isn't enough help, financially". Would anything have prevented her putting on weight? "I think it needs to start in schools. They need to educate kids when it comes to cooking - the most I ever did was decorating a biscuit." She talks about reading magazines and trying every diet they print. "If you know nothing about nutrition, you will follow these diets but they are so unhealthy. These magazines print them, but they have nothing to back up that they work."

Her attitude to food has changed. "I don't want chocolate any more. I'd rather make my own stir-fry than go out for fish and chips. Now, if I feel a bit depressed, instead of having a bar of chocolate, I go to the gym for an hour. We had cooking lessons and they teach you right from the basics, like how to hold a knife, how to cut up a chicken. We had nutrition classes, and learned how to read a food label. They teach you all the myths of various diets, like the Atkins."

Powell is chatty and confident, and says: "It was the most amazing thing I've ever done and it has completely changed my life." She has applied to go back next year to work as a counsellor there. What would her future have been like if she hadn't done something about her weight now? Was she worried she would get worse? "Definitely. I was scared of putting more and more weight on as the years went by. I was scared of developing diabetes. I was scared of never getting married because I was too fat and nobody would want to marry me. I was scared that if I had kids, they would be fat. Now, I want to be as healthy as possible."

Ricardo Lobo-Morell, 33

Three years ago Ricardo Lobo-Morell, who lives in east London, weighed himself for the first time. He had to go into Boots to use one of their weighing machines - he was 30st.

"I thought, 'Bloody hell, I've got to do something about it.' I felt like I was on display in the shop and I knew everyone was thinking, 'Oh, look at the fatty on the scales.' A few weeks later, on the tube, I was sitting on one of those pull-down seats and it broke underneath me. I was so embarrassed but I just made a joke to cope with it. That was it - I knew I had to do something."

Lobo-Morell's weight has brought him the kind of chronic health problems that experts fear will become more common with the so-called obesity epidemic. "I developed type 2 diabetes so I have to inject myself with four different types of insulin four times a day," he says. "I've got high blood pressure, high cholesterol, problems with my knees." He can never remember a time when he was a healthy weight. "As a kid, I was referred from dietician to dietician. Most of them were not particularly sympathetic. I would be given diet sheets, but I would nick money from my mum's purse and buy chocolate on the way to school. My mum would try her best, but even now, when my parents visit me, my mum always comes with food; I think it's her way of showing how much she loves me."

For Lobo-Morell, eating seems to be more of a habit than an emotional crutch. "I don't think there was a specific event that happened that made me pile the weight on. It's always been there and a part of me. I've never been a binge eater but I graze in the evenings. Cheese is the big thing I love. I just love my food, the wrong food, and for me the big thing is portion size. My stomach is so huge now that a little portion is not going to fill me up. I've never felt full. The only reason I know when I've felt full is if I think I'm going to be sick." Why can't he stop? "I don't know. [Eating healthy food and doing exercise] is easier said than done. I know what I need to do, but when you're as overweight as I am - nearly 24st - the light at the end of the tunnel is so far away and I have zero will power." One of the worst things, he says, is thinking about how other people might see him. "This might sound weird, but when I see other fat people it disgusts me. I'd hate people to think that about me, but I know they probably do."

Lobo-Morell, who is a psychiatric community nurse, has tried many diets and has been on anti-obesity drugs. He knows he should be cooking healthy meals from scratch and eating lots of vegetables, but "I just didn't like them". He has been trying to eat healthily and lose weight because after more than two years of convincing surgeons he is a good candidate for gastric bypass surgery, his appointment has finally been booked. "People think it's a quick fix, but it isn't. It's major surgery. I have lost friends over it who think it's the easy way out and aren't supporting me. I want to get my life back and start afresh."

What might have stopped him putting all that weight on? "Perhaps if I was targeted at a young age, and more sympathetically," he says. He thinks "fat camps" would have worked for him. "Food is only part of why someone is obese. There's the psychological stuff, and if you can target that it would help. I was never offered anything like that. I have only seen a psychologist now I'm having surgery. I'm a mental health professional so I know the importance of that."

I call Lobo-Morell a couple of weeks after he had the operation. He sounds tired. "I had mixed emotions on the day," he says. "It was strange walking into the operating theatre and getting up on the table. When I woke up I was in quite a lot of pain, and I immediately regretted having it done because I was attached to lots of drips and I felt quite claustrophobic. But that didn't last." He lost one and a half stone in the three days he was in hospital and the weight has been gradually coming off since then. "I've got no regrets," he says, though admits it is hard to follow the special diet of pureed food for six weeks before he can introduce solid food. "But I don't feel hungry. I don't miss the food I used to eat. My diabetes has got much better, my blood pressure is OK. It is early days, but I do feel positive".