When I was a child, we used to drive every summer up the Great North Road from London to Scotland to visit my grandparents in Lanarkshire, and sometimes we would spend the night on the way in the George Hotel at Stamford. I always looked forward to this, because there was a picture on the ground floor of the hotel of somebody my father assured me was the fattest man that had ever lived - Daniel Lambert, the "fat man of Stamford". Lambert was actually born in Leicester in 1770, but he died at the George Hotel while on a trip to the races in 1809, and so became associated for ever with the Lincolnshire town. He weighed 52 stone 11lb, and the circumference of his waist measured 9ft 4in. It took more than 20 men to lower him into his grave.

Lambert turned out not to have been the world's fattest man, after all. According to the Guinness Book Of Records, that distinction belongs to an American, Jon Brower Minnoch, who is said to have weighed more than 100 stone when he died in 1983, aged 42, in Seattle. But Lambert was certainly a colossus. He weighed nearly three times as much as the popular American dietician Robert Atkins, who was recently exposed as having weighed 18 stone 6lb at the time of his death last year, making him, too, technically obese.

Obviously, Lambert was in a terrible state. On the other hand, he was much liked and admired. He was considered so wise that people were willing to pay money to have conversations with him, and that was how he earned his living. And the portrait that I used to study as a child in the hotel made him look very endearing, despite his enormous bulk.

I remembered him with affection as I read the newspaper headlines last week about how Britain is facing an obesity "timebomb" - an odd word, timebomb, that seemed to imply that an awful lot of fat people were suddenly going to explode. In fact, it meant that by 2020 at least one third of adults in Britain were going to be obese (as measured by what doctors call the body mass index), with dreadful consequences for their health and for the exchequer, unless they changed their eating and exercise habits forthwith.

Already most of us - 70% of men and 63% of women - are officially said to be "overweight", meaning heavier than the "ideal" weight prescribed by the medical profession. And this condition, though falling short of obesity, is also considered very bad. The panic is on. We must get thin now, or face a terrible future.

But wait. If fatness is so reprehensible, why is it that fat people are generally liked and trusted more than thin ones? "Let me have men about me that are fat," said Julius Caesar in the Shakespeare play. "Sleek-headed men, and such as sleep a-nights. Yon Cassius has a lean and hungry look; He thinks too much. Such men are dangerous."

"Who ever hears of fat men heading a riot, or herding together in turbulent mobs?" wrote the 19th-century American writer Washington Irving in his History Of New York. "No, no, 'tis your lean, hungry men who are continually worrying society and setting the whole community by the ears."

I was watching Question Time on BBC1 last week, and Roy Hattersley was much the most popular member of the panel. I couldn't help thinking that this was partly because he was also the fattest. And would Winston Churchill have enjoyed such trust and confidence during our darkest hour if he had been thin and wiry like Robin Cook? (Churchill, by the way, was over 90 when he died, so a little of what you fancy doesn't necessarily do much harm.)

Me, I am usually fairly thin, but once, when I was in my 20s, I was treated for a chest complaint with heavy doses of cortisone that made me swell up until I came to resemble Orson Welles. It changed my whole character. I was relaxed and hearty, with a fruity laugh. Then the end of my medication restored me to my normal, edgy, nervous self.

I accept that obesity is a tragedy for those who suffer from it, but it strikes me that a little corpulence is no bad thing. It reassures people and makes them feel safer and happier in your company. If even a freak like Daniel Lambert could have this effect on people, then perhaps we should all strive to be just a little bit above our "ideal" weight.