I HAVE had to get used to people I have not seen for a year or so sidling up to me at receptions with a concerned look on their faces.

'Are you well?' they ask, with something more than the usual, polite tone of inquiry.

'I'm fine,' I reply. 'I've lost a lot of weight, but I've done it on purpose.' Decoded, what I am really saying is: I don't have Aids; I've been dieting.

'You look great,' they then say, shifting gears rapidly. 'How did you do it?'

'Easy. I just got used to being hungry.'

Everyone wants an easy way to lose weight, and are disappointed to discover that there is nothing more to it than not eating as much as you need to meet your daily energy requirements. The only trick to my method was to take it slowly: for a year I ate a little less than my everyday needs. Along the way, I began to exercise - mainly cycling for an hour about three times a week. As I grew fitter and more enthusiastic, I began to bear down harder on my previously undisciplined eating.

Losing weight is, intellectually, the simplest thing imaginable; but it is one of the hardest psychologically. Motivation is the difficult part. You have to want to lose weight more than you mind being hungry. In fact, feeling hungry has to be taken as a welcome sign that your body is getting less succour than it needs, that it has started to consume its surplus fat.

I lost an average of a pound a week for a year; and then stopped (that's about three and a half stone). My motivation was initially supplied by a couple of snapshots. In one, I was caught in the act of being tipped out of a rowboat: like the Hindenburg, I hovered between sky and earth, a great airship obscuring the horizon. In another, I have my arms around two women, who appear like children nestling up to a giant teddy. These photographs were nothing like my self-image, and when everyone said they were wonderful likenesses, I grew worried.

Somehow I had been lying to myself about how overweight and unfit I had become. I knew what to do - I had lost three stone in nine months in 1984 as part of a magazine article assignment. With self-discipline, I could do it again.

People who don't want to lose weight badly enough to take the straightforward road of modest abstinence and light exercise remind me of the student who asked me at university how she could get a First in her exams. 'It's easy,' I told her. 'To begin with, you learn the subject inside out, and then when you get to the exam room . . .' There was no need to finish the sentence; her face had already fallen.

Dieting is similar. If you do the work, it's easy. Like many things in life, though, it is harder to start than it is to complete. At first, the hunger is great, as the habit of eating for pleasure at all hours and in all amounts has not yet been broken. As time goes on, it is easier to eat small portions and avoid rich desserts. Hunger pangs subside, and the delight of being lighter gives added incentive.

I have discovered two curious advantages to shedding my rolls of fat, and two unexpected disadvantages. The pluses are, first, that clothing fits better: shirt-tails stay tucked in, trousers stay in place; and, second, it is easier to balance on a bicycle or stand up in a bus: this is because one is less top-heavy as the big belly melts away.

The disadvantage is that you grow weaker as you become lighter. This must be what makes fat bullies able to throw their weight around. To compensate for my slighter strength, I have begun to work out with weights.

I kept my spirits up in the beginning by weighing myself once a week, and entering the new weight on a graph developed on my home computer (see illustration). I was comforted by watching the declining line and the fact that I was meeting - or only just missing - lots of small, interim goals.

At first I just hoped for the best; but now I have learnt something of what I was up to. I consumed about 2,500 calories a day, about five-sixths of my daily needs (about 2,900 calories). That is a shortfall of 400 calories a day, or 2,800 calories a week. The body burns a gram of fat for every six calories it needs to make up the daily shortfall: thus 2,800 calories is worth about 460gm of fat a week. And that is about a pound a week weight loss, or a stone every 14 weeks.

Of course, if, like me in 1984, you go back to full, unthinking indulgence afterwards, you will have to do the whole thing over again a few years from now. Perhaps this time I should put some 'before' photographs on the wall: they might help to keep me on the straight and narrow.