The answer to being too fat is utter self-delusion

Icaught sight of some fat, pompous ass haranguing a bunch of attractive women at a party the other night. He was on the far side of the room, clutching a poncy cocktail the colour of a 1970s duvet cover and declaiming God knows what to these poor girls who appeared hectored and harassed and kept checking their watches.

He looked a bit like me, this self-satisfied git, except more addled and ancient and even more pleased with himself. At least have the dignity and self-possession to hold your stomach in, you paunchy, fatuous idiot, I muttered to myself, having taken an instant and violent dislike to the fellow. Everything you're telling those women is somehow, horribly, negated by your big gut, I added, as a spiteful afterthought.

And then guilt crept along. I started lamenting such bitchiness and began to feel ashamed. True, this was a party for jabbering media monkeys, and bitchiness was therefore a non-negotiable condition of entry. But, as Dr Kelly's widow has exhorted us all, we should really show more kindness and compassion to those whom, for whatever reason, we heartily despise or revile. So I looked away, a little chastened, and silently wished the chap all the best, by means of recompense.

A few minutes later one of the women with whom I was engaged in conversation made a comment about the voluptuous room we were in. Imagine, she said, having the whole of one wall of a room covered by mirrored glass.

'Mirrored glass?' I asked, my voice faltering a little.

'Yes,' she said, puzzled that I hadn't noticed. 'Look over there.'

And so I looked, and saw.

It's an unusual state of affairs to feel compassion for yourself because you've been the apparently unwitting victim of your own contempt and vindictiveness. It's the sort of thing which leads — ineluctably, I would guess — to severe mental illness. But what bothered me most, as I stared headlong into the huge mirror, across acres of polished pine flooring, past Alan Rusbridger and Melvyn Bragg and the controller of BBC 1, was not the metaphysical ramifications of my self-loathing, but the great big gut. Where the hell had that come from? I wondered.

I used to be Biafra-thin. Thing is, I still think of myself as Biafra-thin, despite the occasional slivers of evidence to the contrary. For example, my son Tyler, who is five years old, recently pointed to my stomach and asked me innocently if I was going to have a boy or a girl. When the copious bleeding from his nose had stopped, and he had ceased crying, I carefully explained to him that it was both overfamiliar and dangerous to make such personal comments about other people. But then, worried, I asked our nanny Cheryl if she thought that I was fat.

'Urn . . . n00000. No. Not at all,' she said. 'I mean, no more than most men. You look like Homer Simpson, more than anything. You're a dad, aren't you?'

This, taken together with the horrible revelation which occurred at that media party, convinced me that I needed to lose weight: and that meant a diet. And at the same time I wondered how things had reached such a lamentable stage.

I think I used to keep thin, in my youth, through the strategic deployment of amphetamine sulphate and masturbation. Both of these burn up the calories, but neither are meet or fitting during middle age. Aside from that, my lifestyle is much as it was 15 years ago and quite possibly healthier, in terms of the food I eat: my affection for Big Macs plus a giant cheery cola has diminished with age.

Anyway, I tried the famous Atkins diet first. I ate nothing but steak for a couple of weeks. It was incomprehensibly expensive, believe me. And it had no effect whatsoever except that, in addition to being overweight, I began to smell bad. Plus, I found that in restaurants, the social stigma of explicitly avoiding carbohydrates was more injurious and embarrassing than the social stigma attached to having a fat gut. So I stopped that, sharpish.

I began a radical diet of eating no food whatsoever. My sustenance, for the best part of a week, consisted entirely of cut price Soave (£5.50 for two bottles) and Jack Daniels, plus many, many cigarettes. To be honest, this was never going to work. It's only a hair's breadth away from my normal diet, if I'm honest.

Quite a few female friends suggested that a fortnight in Goa was the best way to lose a stone or two. You fly there, drink the water and eat the food, and by the morning of day three you're camped out in the lavatory in receipt of nature's own peremptory and apparently perpetual form of colonic irrigation. 1 didn't have the money for the flight, so I poisoned myself with some undercooked eggs and very old corned beef which had been left on top of the fridge next to the cat food. After three days immobilised, prostrate on the sofa, I was visibly thinner, at least six pounds to the good. This is the only diet I tried which actually worked. But hell, it was a miserable three days. And for those three days I was unable to work, which cost me a couple of grand.

I tried salads and running. My God, the misery of those few days. Let me tell you, amphetamine sulphate and masturbation are both far preferable. I even tried supermarket low-cal Healthy Eating Stay Slim gloop and slime (taste-free rusks made of polystyrene, and soup the flavour of semiskimmed water) but this was desperate and depressing — plus I felt as if I was turning into a woman. A couple of days into this diet and I noticed my breasts beginning to swell, and bud. I began to deal with other human beings in a caring, consensual way, started taking an interest in soft furnishings and lost my sense of spatial awareness.

But there's a happy ending. Because the truth is that right now I look like Johnny Depp. At least, I think I look like Johnny Depp. I have a washboard stomach and cheekbones as sharp as knives. And the answer, in the end, was to eschew this shallow and debilitating fixation with vanity and the outward appearance of the self and to institute a rigorous regime of utter delusion, To wit: never look in a mirror at a distance of less than 12 feet. Never, ever, weigh yourself. Only speak to people who are sufficiently polite not to mention your physical shortcomings. Eat what the hell you like, with unconstrained abandon, and drink more and more to encourage the delusion. Smoke cigarettes as an aid to insouciance.

And thus remain, in your head, 16 years old, happy, whippet-thin — and to die for.