I HAVE HEARD some hilarious excuses from fat people in my time, but the one rolled out in the last item of yesterday’s Today programme managed to flabbergast even me. Indeed, I dare say that obese people all over Britain were so delighted by this new chance to blame their condition on something other than their own moral turpitude that many of them choked on their cornflakes. Except that by 8.53am they had probably already wolfed down their cornflakes and were well onto their third plate of scrambled eggs and bacon with pancakes and maple syrup.

While making a documentary about the obesity crisis for More4 this year, I went to great trouble to show how such excuses as “I’ve got a slow metabolism”, “it’s genetic”, “I can’t afford healthy food” and “I’ve got an underactive thyroid” were in most cases as meaningless and self-deluding as “I’ve got heavy bones” and “like Superman, I have infinite mass”.

I little dreamt, however, that the health editor of The Ecologist, Pat Thomas, would soon be attempting to persuade us, by way of a report in her magazine and a debate on Radio 4, that the critical rise in obesity in the past 20 years has been caused by . . . pollution. According to Ms Thomas, fatness is caused not by greater intake of calories than output but the debilitating effect on the body’s metabolism of pollutants such as organophosphates and organochlorines. If you eat a burger in a city, Ms Thomas appeared to be saying with an entirely straight face, it will put more weight on you than if you eat it in the New Forest.

Staggering hokum, I know, but the BBC gave it airtime, allowing this woman to draw the most bogus anecdotal conclusions from the fact that obesity is rifer in cities than in the countryside (ignoring socio-economic issues, opportunities for exercise, the starch-based convenience food diets of deskbound office flunkies, etc) in a way that allows our growing legion of lard-arses, who should be radically altering the way they live, to get off the hook once again.

But if it is pollutants rather than diet and lifestyle that make us fat, then why, pray tell, have urban dogs and cats not got fatter at the same rate as humans? Metropolitan Police horses, who plod along with their noses at exhaust level all the days of their life, should be the size of elephants. London pigeons should be too fat to fly, town mice too porky to squeeze into their mouseholes.

If there is a relationship between pollution and obesity to be looked at, then it is surely the way in which obesity makes people significantly more vulnerable to the effects of pollution. A study of 611 Boston children by the Harvard School of Public Health in 2004 found that when air pollution levels went up, obese youngsters had an 11 per cent decrease in lung function, compared with only 2 per cent in children of normal weight. Being fat, in other words, makes you five times more vulnerable to your contaminated environment. What our wheezing porkers need is a wake-up call, not the consolation of sham excuses.

That said, one’s sympathy for fat people is severely mitigated by their consumption of more food and energy than those who sustain a more traditional mass and volume (creating more packaging waste and requiring more fuel to heat and cool and transport them) and thus create more pollution. Pollution doesn’t make you fat; being fat causes pollution.

And another thing: I spent the first four days of this week in Tokyo, and if pollution makes you fat then why, in a city so polluted that a good proportion of the workforce feels compelled to walk the streets in face masks, did I not see a single person even as chubby as me? I went, in a bound, from being the thinnest man in London to the fattest man in Tokyo.

Indeed, after a couple of days among these beautifully dressed, impeccably polite and helpful, slim and well-groomed people, I had almost forgotten what a race of fat, feckless scruffs my own compatriots have become — until I caught sight, on the third morning, of a vast-arsed European male in shorts and trainers galumphing wheezily up the street towards me, looking for all the world like a giant toddler.

In Japan, only schoolchildren wear short trousers. Once past 10 they dress, as we used to in Britain, like adults, in well-fitting, modest clothes and lace-up shoes. Why did the flabby tourist not have the decency to identify the cultural inaptness of his appearance and modify it with more suitable clothing, or stay at home?

An even heftier reminder of the crisis in Britain came at Tokyo airport when I was checking in, where three Englishmen of 18 stone each or more stood in front of me, their feet wide apart in that stability-maintaining stance to which the morbidly obese resort, wearing the first tracksuits I had seen since I arrived (for I had attended no athletics meetings) and clutching vast Starbucks tubs of warm frothy milk drinks, just like mother used to express. This tubby triumvirate looked not like toddlers, but bona fide babies.

Did we start dressing as infants because we got too fat to be comfortable in grown-up clothes, or did we eat ourselves into the shape of babies because once we were dressing like them we thought we might as well look like them? I’d say it was a chicken and egg question, except that two thirds of you (according to statistics) don’t need to be reminded that it’s ten minutes since you last ate something.

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