There is no doubt: as a society, we are groaning under the weight of the obese and if we do not do something about it soon, it will cripple us.

As a doctor, I have been concerned about this for many years. I have seen more and more obese patients clogging up the waiting room but, most worrying of all, there is a perverse expectation that no one, including doctors, should criticise them for being overweight.

The height of lunacy was reached a few years ago when Nice, the NHS regulatory body, suggested that doctors should not even refer to patients as ‘obese’ in case it offends them.

As a society, we are groaning under the weight of the obese and if we do not do something about it soon, it will cripple us

There were stark warnings yesterday from the World Health Organisation that two-thirds of women and three-quarters of men in Britain will be overweight by 2030. They warned that we are facing an ‘enormous’ crisis if it is not tackled.

By the end of the decade, obesity will be a bigger cause of liver failure than alcohol. It’s not old people or dementia or cancer that will cripple the NHS: it’s the overweight.

The health service is already buckling under their weight. A report commissioned by the management consultancy firm McKinsey and published last year found the problem costs the country £47 billion a year. That is just under half the entire NHS budget. Managing obesity-linked type 2 diabetes alone costs us £10 billion a year.

While health economists warn gravely that we need to find £8 billion over the next five years to plug the NHS funding gap, that is a fraction of what we are paying out each year simply because people are too fat. We could sort out all the NHS’s funding problems in the blink of an eye if people would lose weight.

I think the State should intervene in people’s lives as little as possible. Individuals should be free to do as they please and to ignore medical advice if they wish, but it is slightly different when they expect the NHS to pick up the pieces for problems caused by a lifestyle choice.

Each of us pays into the NHS in the expectation that we will do our best not to use it unnecessarily; in the knowledge that there are finite resources. Which is why I believe we should stop talking about being fat as though it were a bizarre malignant affliction and talk, instead, about self-control.

Each of us pays into the NHS in the expectation that we will do our best not to use it unnecessarily; in the knowledge that there are finite resources

While people are free to eat as much as they like, they cannot expect doctors like me to keep quiet about the effects of doing so, especially when their behaviour is going to ruin an institution I love and want to see protected.

People heap opprobrium on the way that politicians handle the NHS, yet their meddling is nothing compared to the ruination it faces because of the overweight.

In some ways, the human body is incredibly complex, but when it comes to fat, it is refreshingly straightforward; if the amount of energy we put into our body exceeds the amount of energy we expend, this excess energy is stored as fat.

It’s that simple; people are fat because they eat more than their body needs.

Now, I accept that there can be mental problems associated with overeating, which is often linked with depression. This deserves some sympathy, but for many, overeating is an indulgence.

If we do not do something, we will not only condemn people to shorter lives, we are guaranteeing that the NHS will not be there for future generations

Yes, people have different metabolisms, but that merely means people have different energy requirements. If you have a slow metabolism, then great, your body is very efficient at using food and you don’t need to eat as much as someone with a high metabolism. It is not an excuse to eat to excess and then claim it’s not your fault.

The problem is that our society has convinced itself that obesity is an illness. For years at medical school, I waited patiently to learn about these strange ‘glands’ that apparently made people fat. I waited in vain — there are no such glands.

It’s not glands — or genes for that matter — that make people fat. It’s cake.

Some people do have such problems as low thyroid activity, but these conditions are easily treated now. For most, there is no valid reason to be obese.

Why has saying this become taboo? Why is it that those of us who are critical of the overweight because of their lack of self- control are censured?

Part of the blame lies with the U.S., where the obese have adopted the language of such persecuted or marginalised minorities as gay or black people, saying they are ‘proud’ of their fatness and ‘celebrate’ it. This ludicrous cult of the obese has now infected us.

But there is nothing to ‘celebrate’ about being so fat you need special clothes and reinforced ambulances to get you into hospital.

The height of lunacy was reached a few years ago when Nice, the NHS regulatory body, suggested that doctors should not even refer to patients as ‘obese’ in case it offends them

There is no reason to be proud of the fact that you cannot sit in an airline seat or walk without a stick. There is no justification for congratulating yourself that you have eaten so much that the sheer weight of your body is gradually killing you.

That attitudes to obesity have changed is shown by a Department of Health study comparing obesity rates from 1967 to 2010.

While people in the Sixties were generally slimmer, what was really telling was that more than 90 per cent of those who were obese then had tried to do something about it and lose weight. By 2010, the number of those trying to slim was less than half. People don’t bother losing weight now; they see being fat as normal.

It is vital that we change this attitude. We need to stop being scared of calling people fat, to remind ourselves that the very viability of our NHS is at stake and that obese people are putting a disproportionate strain on health services.

Above all, doctors should have the responsibility to tell people when they are fat and encourage them to lose weight.

As I have said, there is undoubtedly a group of obese people who have underlying psychological problems. As a psychiatrist, I meet many of them in my out-patient clinics.

While people are free to eat as much as they like, they cannot expect doctors to keep quiet about the effects of doing so

That is not to absolve them of responsibility for their weight, however, but unlike most obese people, they very often desperately want to lose weight and wish they could stop using food to manage their emotions.

Indeed, they come asking for help. Unfortunately, the psychological support they need is sorely lacking and if we are going to tackle the obesity epidemic in any meaningful way, then part of that involves providing better support for these people.

Most obese people simply do not care about being overweight. When they need their joints replaced, when they need heart surgery, when they develop diabetes, they expect the health service, which means other taxpayers, to foot the bill.

We should make such an attitude socially unacceptable.

That’s not to say you have to be cruel but we do have to stop being complicit in people’s obesity by remaining silent. We also need to address the issue of what is making everyone fat.

There is no doubt that, for the first time in human history, there is a plentiful supply of calorie-dense foods.

Up until about 50 years ago, the main problem facing the human race was finding enough calories. But now we have so many our bodies can’t cope. The way to help fight this is a fat tax.

People often mistakenly think that eating fatty foods is the cause of getting fat, but the real problem is refined sugar.

Sugar is packed with energy and it is everywhere, from savoury snacks such as crisps to chocolates and cakes and fizzy drinks. We need to make calorie-dense foods, those containing high levels of sugar, more expensive.

Heavy taxation has been successful in reducing smoking, which just a few years ago was considered so socially acceptable you could do it pretty much anywhere, yet now is roundly frowned upon.

We need to do the same thing with fatness. The revenue raised by a fat tax could subsidise such healthy foods as fruit and vegetables and fund psychological help to support those who struggle to lose weight.

Make no mistake, the food industry does not want to see this any more than the tobacco industry wanted to see legislation to curb smoking; it will fight it.