Ginevra Tamberi, a 21-year-old film studies student from Rome, has very tall, very skinny parents. Her brother can eat 4,000 calories a day and remains one of nature's giraffes. But Ginevra is not so lucky. She eats one slice of bread and it goes down her throat and directly on to her bum.

Ginevra tried everything: the Aktins diet, the Dukan diet, the Scarsdale diet, the Zone diet, the cabbage diet, the onion diet. She saw a private nutritionist and a personal trainer. All to no avail.

In desperation she visited the plastic surgeon Marco Gasparotti. Ginevra says, "Everybody in Rome knows Gasparotti." And everybody does, too: you cannot throw a brick in Italy and not hit Dr Gasparotti demonstrating his innovative techniques on some TV chat show. For Gasparotti is no slouch; he has a liposuction cannula to his name and has patented an elastocompressive cellulite-busting girdle called the Lipo Contour Elite Capri. He has also garnered countless international awards, and is at the very forefront of innovative ways of redraping skin and sucking out and resculpting fat that cannot be described to readers looking at this magazine over breakfast.

Ginevra went to Gasparotti for liposuction. She wanted, as it were, to be vacuumed down a couple of dresses sizes. But Gasparotti was not encouraging – liposuction, he said, was for improving shape and contour, not for comprehensive fat removal. Instead, Gasparotti had another, better trick up his sleeve: the Diet Tube. A week later, after some medical tests, Ginevra returned to Gasparotti's clinic and she came out with a piece of plastic tubing sticking out of her nose. One end of the tube went down into her stomach, the other was attached to a small electric pump.

For 10 days Ginevra wore the nasogastric tube. She ate nothing and the pump, working day and night, sent tiny amounts of a protein-filled liquid into her stomach to stave off hunger. The tube, she says, didn't restrict her lifestyle. When she went out, she just popped the pump into her Prada bag and nobody in the street seemed to notice she had a tube up her nose. I find this surprising. Normally you notice when people have tubes up their noses, just as you also notice when they are wearing gas masks. But Rome is Rome.

On Diet Tube Ginevra experienced occasional moments of lassitude, but mostly she felt great. She says, "It was purifying everything. My skin was, like, unbelievable. It was so clean, so pure, like a baby's. Amazing!" Ginevra grew used to the faint buzzing of the pump, and didn't feel nauseous or hungry. But she did miss chewing. "So I was just having tea – green tea – all the time."

Didn't she get sick of the tea?

"If I see green tea now, I am going to die."

And what did her friends think?

"They're used to my strange stuff, my weird things." And anything was better than the onion diet.

By the end of the 10 days, Ginevra had lost 7kg. She gave Diet Tube a break. Six months later, she had another go and lost a further 5kg. She is now a size 14, not a size 16–18. Her friends and family have also tried it. Ginevra's aunt, another of the family's non-giraffes, has lost 30kg. "My aunt is so happy, she could live on Diet Tube. I saw her with it and she was feeling so powerful. She was really putting herself into her cooking, making lasagne and parmigiana and polpettone and Mont Blanc."

Last year, 1,500 patients underwent Diet Tube. Numbers are escalating – there are now eight Diet Tube clinics in Italy, centres in Barcelona, Athens and Madrid, and franchise negotiations underway for a dozen other countries, including the UK. The fact that such an outlandish procedure can flourish is hardly surprising. As a nation we are getting fatter and fatter. We are also watching too many makeover TV programmes and becoming increasingly susceptible to the idea of the quick fix. Ten Years Younger, and Extreme Makeover have a lot to answer for. Invasive beauty procedures have been normalised and there are so very many to chose from : face-lifts, eye tucks, tooth whitening, Botox, liposuction, laser, chemical peels, silicone injections, collagen red light therapy… By the time you are 50, you no longer have the face you deserve, but the face you can pay for.

The same holds true for waistlines. If, for whatever reason, you are not up to dieting or spending time in the gym, there are other short cuts. You can experiment with hypnotherapy or with algae or with Peter Foster's spooky remedies. Or you can resort to non foods: egg white omelette, zero calorie jelly, oat bran, the abominable Dukan pancake. Or, you can take a very big breath, brace yourself and go for weight loss (or "bariatric") surgery.

Here are the main options: gastric band, gastric balloon, gastric bypass and the relatively new gastric sleeve. I looked up my local weight-loss surgeons, the eminently respectable Bariatric Group. Their website goes into painful detail. The least invasive procedure is the gastric balloon, which fills up the patient's stomach and gives them a feeling of fullness. The procedure is done under sedation: a silicone balloon is inserted endoscopically into the stomach and then filled up with blue saline solution. Why blue saline? Just in case the balloon bursts and starts to travel down and block up the intestines. The video voiceover says, "So if you do have a puncture and you start peeing green, then you know there's a problem." You bet.

The balloon is only temporary – it has to come out after six months. All the other options are permanent (though the band is reversible) and require a general anaesthetic. They all involve reducing the capacity of the stomach to a lesser or greater extent. The most extreme option is the gastric bypass, in which a section of the top of the stomach is stapled off to create a little pouch that is then attached directly to the intestine. The diagrams show just how radical this surgery is: all that the patient can use is a tiny pocket of stomach, and the now redundant, bypassed stomach and a tail of intestine are left lying there in the abdominal cavity like a dead puppy.

A gastric bypass is a major, make or break operation. Most patients are hugely fat and unfit, and 0.2% of them will die during or as a result of the operation. But the most common bariatric procedure in the UK is the gastric band, which involves an inflatable silicone ring being placed around the top of the stomach, thus reducing how much the patient can eat. The ring is connected to a filling port by a thin tube, so the band can be tightened or loosened by adding or reducing the fluid in the port.

A number of celebrities have had gastric bands: Fern Britton, Anne Diamond, Vanessa Feltz, Sharon Osbourne. But many normal mortals have also had the operation. Hollie Rogers, 23, had a gastric band fitted privately by the Bariatric Group when she was 19 and weighed 17 and a half stone (111kg). Her mum paid – nobody else knew how miserable being fat was making her.

The surgery, according to Hollie, was not a big deal. She had a pre-op diet, then one night in hospital for the operation itself and then a series of follow-up appointments at which they gradually filled up the port and tightened the band. Three years on, she has a one inch scar that "has pretty much faded." What's more, she is rather pleasingly bionic – with a slightly knobbly bit "underneath my boobs and above the middle of my belly button" where the port lies.

Thanks to the band, she has lost six and a half stone (41kg). The band, she says, "forces you to change your eating habits. It forces you to eat less." In the old days, she'd have had her dinner and a couple of hours later would settle down to a takeaway or a bag of chips. Not now. "I eat the same amount as anyone who is eating healthily. And I can eat most things, except steak and bread. I mean, I can have one slice of bread, but not eight rounds of toast, which is what I did when I was overweight."

She has never regretted the operation. She says, "I'm so glad I didn't wait. In your 20s you want to go out and have fun. Before, I always felt I'd stand out for the wrong reason." Hollie has released her first album. Recently, she went on a snowboarding holiday. She is having fun.

Thinnies can never know the misery and frustration suffered by the very overweight. It is a hellish cycle to be stuck in: the more you eat, the larger and hungrier you get. The larger you get, the harder it is to move and the more humiliating it is to put on a swimming costume. So you settle back and eat more. Eventually you reach the catastrophic tipping point: you are too large to exercise or even get up and down the stairs easily, and the biochemical regulatory systems in your body (the naturally released enzymes that suppress appetite) stop working properly. Now you are never sated. All you want to do is eat, eat, eat.

At this juncture, losing even as much as a stone (6.3kg) won't do much. To make any appreciable difference to your health outcome – to reverse your type 2 diabetes, and get you off your blood pressure tablets and give your knees a rest and lower your cholesterol, you have to lose seven or nine or even 15 stone. For that, you will need to spend a very long time on a very low-calorie diet, and have the willpower of a Latin American despot.

Technically there is no reason why someone who is very heavy – 20 or 22 stone, say – should not be able to lose weight. But the surgeons think otherwise. Richard Welbourn, the clinical director of the Bariatric Group, calculates the answer thus: "If you have a Body Mass Index (a measurement based on an individual's height and weight. A healthy BMI is anywhere between 18.5 and 24.9.) of 40 and you are seven stone overweight, it would be like walking across the Atlantic and running five marathons. That is the straight calorie equation. And running marathons makes you hungry."

Meanwhile, Alberic Fiennes, president of the British Obesity and Metabolic Surgery Society, says, "If you have a BMI of 40-something, and you've been that way for several years, it is overwhelmingly likely to be irreversible – whatever the thin people think."

Eating, Fiennes says, is in part an involuntary process: "It'd be like asking someone to hold their breath for 15 minutes. Most people can do it for one minute, or two minutes, or maybe four minutes if they've been doing diving practice. But 15 minutes? You can't. You have to breathe. And when you breathe, you gasp."

"There is a moral stigma to obesity," continues Fiennes. "These people are seen as weak, and stupid and greedy. But obesity is a disease."

Fiennes believes it is outrageous that we aren't carrying out more bariatric surgery. There is, it seems, a postcode lottery with many primary care trusts and commissioning groups refusing or hugely restricting access. Last year, around 4,000 bariatric operations were carried out on the NHS. Yet, according to the guidelines set out by Nice (The National Institute for Health and Clinical Excellence), adults with a BMI of 40 or over (or a BMI of 35 with co-morbidities) should be considered for surgery. That means – shut your eyes for a minute before reading this frightening figure – 1.2 million people in the UK are eligible. We really are becoming a nation of whales.

There is no doubt that bariatric surgery, when carried out with the right medical and psychological pre- and post-operative care, can be hugely beneficial. It prevents premature death, vastly improves quality of life and is very cost-effective for the NHS (a recent study showed that 85% of severely obese patients with diabetes no longer suffered from the disease two years on from surgery). Dr David Haslam, a GP and the chair of the National Obesity Forum, says "I've seen hundreds and hundreds of people's lives transformed by bariatric surgery. It is positively life-saving."

Nevertheless, bariatric surgery should be treated with extreme caution – as should any operation that entails removing or drastically curtailing a vital organ of the body. And while surgery opens some doors, it also sometimes seems to close others. A very low calorie diet maintained over months or even years is going to be a painful and uphill road, impossible to keep to without enormous amounts of moral support. But why would anyone – patient or health carer – persevere on such a programme when a permanent surgical remedy is available?

Take the case of Justine, a 49-year-old journalist who weighs over 20 stone (127kg). She has had weight problems since the age of four, when her teenage mother first put her on a diet. Two years ago she went to her local GP surgery to join up with Counterweight, an NHS-funded diet programme that provides one-to-one support to people wanting to lose weight.

This is Justine's story: "The nurse said, 'I can't see you – you are too heavy for Counterweight.' She told me that if you are over a certain weight or BMI, they send you to hospital. So, I went to my local hospital – it was a very strange meeting. I went along to see the doctor for what I thought was a meeting about Counterweight. He said, 'What we find is that people of your age and weight find it impossible to keep the weight off. The only answer is surgery.'

I said, 'That seems a bit radical. Do you have any other solutions?'

He said, 'Well, not really, but would you like to see the dietician?'

"About seven and a half months later, I finally get the meeting with the dietician and I get on the scales and she was talking about surgery. And I said, 'Is there no other option?'

She was very surprised. She said everybody wanted it – they were biting her hand off to get surgery. And I was apparently a good contender. Surgery: that was all they were interested in."

So she went along to have her hand held, and all they wanted to do was cut her open?

"Yeah," she says bleakly. "Something like that."

There is a madness in our mindset about food. How can we have got so fat? How can we have failed so dismally to get so many people to eat properly? A lot of work on healthy eating is already done in schools and in GP surgeries, but the message isn't getting home. How can it when food that is bad for you is so much cheaper, crunchier and more convenient?

Hopefully one day, when we have banned crisps and all orange breadcrumbed food, we will look back on today as the Dark Age Of Obesity. Maybe by then we will also have finally developed a safe appetite-suppressant drug and bariatric surgery will all but disappear. There is a precedent for this – when the drug cimetidine became available in the late 1970s, patients stopped being routinely given gastrectomies for gastric ulcers.

In the meantime, desperate patients can always travel to Rome for their nasogastric tube. Over a crackly telephone line I ask Dr Gasparotti about the Diet Tube diet. "It's not a diet," he says quickly. "It's wrong to call it a diet. It is a nutritional protocol. A very strong motivational therapy."

What's so wrong with diets?

"Diets take too long. You say to these people, 'It is very important, so keep to this diet and come back and see me in three or four months.' They can't do it. They go out to supper with a friend. They eat. But I say to them, 'Give me 10 days of your life, OK? In 10 days you will have lost between 8% and 10% of your body weight. Don't worry. You will get thinner. It is mathematical! It's biochemical, OK?'"

OK.

"So it's a fast – but with proteins. And as there are proteins, you don't lose any muscle. You will eat nothing because you won't be hungry. You won't have any inconvenience. You can carry on working. You can have a shower, you can go swimming. We don't recommend going to the gym for the first week, but these people don't go to the gym anyway. And..." He pauses before the punchline: "You slim while you sleep!"

Gasparotti explains that Diet Tube was originally devised for the very overweight – for "enormous obese people who couldn't even move". He says, "We don't just give it to anyone. You have to be over 18 and in good health. If I began to give it to girls who just wanted to lose two or three kilos, they'd shoot me!"

But a minute later he adds, "Understand. It is obvious. I have to say that in rare cases…" – at this point I can almost hear him rolling his eyes – "unmotivated people who aren't able to move around much and are very lazy and want to lose eight or nine kilos. Well, of course one can do it for them, too."

So if I get on a bus in Rome, will I see people with tubes in their noses? "It's become a pretty common thing now. You see lots of lawyers and businessmen going about the city with their tubes and their briefcases."

Isn't that a bit extreme?

"Look," he says darkly, "our life today is very neurotic, very fast. Nobody looks after themselves."

Has he tried Diet Tube himself?

"Yes! Stavo benissimo. I felt happier. It was euphoric making."

Like a medieval saint on a fast?

"Well, yes! Once, there was a week of fasting at Lent. And you only ate fish on Fridays. That's all gone now."

• This article was amended on 14 March 2012. The original stated that Dr Gasparotti's Diet Tube method was new. This has been corrected.