No need to ask who ate all the pies today. Say hello to the Chawner family: Samantha, 21 (18 stone), mother Audrey, 57 (24 stone), father Philip, 53 (ditto), and baby Emma, 19 (17 stone, the same as a newborn elephant). Total: 83 big ’uns.

Yup, they’re fat. Disgustingly fat. But that’s not the only reason we were encouraged to laugh and point at the Chawners last week. This fatty family is also on supersize benefits: housing, unemployment, disability – you name it, they get it. The Chawners are all permanently latched on to the teat of the state and guzzling to the tune of £22,508 a year.

They made sorry reading. Philip developed weight-related diabetes and gave up his job as a lorry driver. Like Audrey, he hasn’t worked for 11 years. “We love TV,” he said. “It’s on from the moment we get up. Often I’m so tired from watching TV, I have to have a nap.” Audrey disclosed her weekly shop, as if to prove how birdlike they were, although the first item was 18 bags of crisps. “We all love nibbling on biscuits. I once bought some pears, but they tasted funny.”

Although they refuse to diet, the Tele-tubby family still feels hard done by. It’s not their fault they’re so fat, they say; someone else should do something.

“What we get barely covers the bills and puts food on the table,” said Philip, who joins 2,000 other Brits in receiving £84.50 a week because they are too fat to work. “We deserve more.”

I admit that when my appalled gaze rested on the Chawner family, I almost had a heart attack myself. In a week when The Lancet published the findings of the biggest survey on obesity, which showed that being quite fat (up to the size of the BBC DJ Chris Moyles) shortens your life by three years, and being vastly fat (the size of a hippo) takes 10 years off your life, the Chawners really did seem to be the poster family for everything that we didn’t want to be as a nation.

Putting the fattist prejudices to a side for a moment, before you rush to “fatty-bait” – the practice of shaming fatsos into losing weight – consider, please, the Chawners’ case from the other side of the elasticated waistband.

Audrey put it best. “It’s not my fault I’m this size. I’d work if I wasn’t disabled,” she said. She didn’t say “hugely fat”. She said “disabled”. And if Audrey is disabled from a recognised medical condition, then who are sizeists like me to judge? People like Audrey know there’s something wrong, that they do not conform to society’s accepted standards.

And, as it turns out, the Chawners and their ilk do have a case to make, and here it is. Susan Ringwood, chief executive of Beat, the eating disorders charity, says those who overeat are, in many cases, as worthy of concern as those who undereat, but for obvious reasons don’t get as much attention as skeletal teenage girls who look almost like size-zero models.

“Overeaters know they are unhealthy. They know about their five a day but it’s no easier for them to make the long-term lifestyle changes to their diet than it is for anorexics,” she says. She also points out that when it comes to the spectrum of eating disorders, those who don’t eat, the anorexics, constitute only 10% – the tip of the iceberg. Most eat too much.

In the US they are way ahead of us. There, obesity has achieved the status of a “disease” even though it is caused by a combination of voluntary and involuntary factors: genes, sedentary lifestyles in the suburbs, the McDiet and an inability for various reasons to lose weight through exercise.

Stateside, the long-term effects and costs of what is regarded as the – sorry – ballooning obesity “epidemic” is the hottest issue in public health. Here, too, where two-thirds of us are carrying too many pounds of adipose tissue, we are beginning to wake up; the word “pandemic” has been applied to the nation’s thickening waistline by Brio, the Bristol University Research Into Obesity.

Dr James Le Fanu, the medical historian and GP, is one clinician who challenges the orthodoxy that chubsters have only themselves to blame. He thinks the cause of obesity is “not known”. He’s seen women on restricted diets failing to lose a single pound. His guess is that we all have thermostats, which govern our “energy balance” – how much weight we lose or gain relative to what we put in our mouths. He also believes that fatness runs in families, from observing this in his surgery.

This is the essence of the Chawner case, too. “We’re fat because it’s in our genes. Our whole family is overweight. Even when Philip went into hospital with septicaemia in 2006 he didn’t lose any weight. And he was eating tiny portions.”

Right, then. Fair enough. I am prepared to concede that being fat or being thin is partly in our DNA. But come on – it’s also a matter of choice, habit, lifestyle. It’s like smoking, drinking, sun-bathing – you can choose to gorge. Only, unlike smoking, which is in decline, more and more of us are “choosing” to be fat, or allowing our children to get fat, and that’s not good for any of us.

According to some estimates, obesity could cost the NHS in England £6.3 billion by 2015 unless the flab is fought. Some councils are having to shell out thousands of pounds on fat-friendly services, such as wider crematorium furnaces and bigger school chairs.

Whatever obesity’s cause, and however sympathetic we may or may not be, it doesn’t matter. Obesity is a national emergency. It is, yes, the new smoking. Rather than see them like animals in the zoo, we should commend the Chawner family freak show for displaying their bulk. They have drawn our horrified eyes to a health crisis that concerns us all.

“So, Nigel Havers was next to me,” I was saying. “And on stage there was this exquisite 76-year-old woman called Liliane in a black velvet catsuit and diamonds, belting out I Never Do Anything Twice in a heavy Parisian accent, while doing the splits . . .”

“Don’t tell me,” my companion said in a bored voice. “And then you woke up.”

“But it wasn’t a dream,” I shrieked. “It was last Wednesday night. And get this. I looked round and saw the Queen of Norway and Paul O’Grady together, applauding.”

Some evenings in London are more bizarre than the deepest recesses of the subconscious mind can arrange. I was at a party to launch the cabaret American Songbook in London, at the Pizza on the Park restaurant. And all the above happened – drag queens and real queens and old queens. Everyone had a marvel-lous time. In fact, come to think of it, I can’t believe it either.

rachel.johnson@sunday-times.co.uk

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