Great news for couch potatoes: exercise is neither safe nor healthy Goodbye Lycra, hello lunch.
"Exercise is bunk," said Henry Ford. "If you are healthy you don't need it; if you are sick you shouldn't take it." According to new research he was right. A recent survey of male joggers has found that despite taking vigorous exercise many suffered expanding waistlines. In conclusion: if you are destined to develop middle-aged spread you will.

The research carried out in California (where else?) found an average 6ft man gained about 3.3lb and about three quarters of an inch round the waist for each decade of their life between 18 and 50 (which only goes to show they weren't really trying; with real dedication I could put on at least 3.3lb in ten days). This was regardless of the amount of miles they ran.

The scientists said their findings were true of exercise in general and warned that the only way to keep weight gain to a minimum was to increase exercise levels as you get older.

The consequences sound truly horrific. If you're averaging 10 miles a week at 30, you would have to be running 24 miles at 40. But then, seeing as we are living longer and mortality rates are improving, you could still be fighting fit at 70 but having to run 66 miles - the equivalent of running from London to Portsmouth every week or indeed running all the way from London to Aberdeen and back again three times a year.

Or if you still wanted a svelte figure at 80 you would be running three marathons a week. And even if you were superfit, running 10 miles an hour that's still a good hour spent jogging every day. Many people have plans for their retirement but they're usually centred on enjoying oneself and garden centres. The prospect of thousands of exhausted seventy-year-olds knocking you off the pavements as they clock up their 3,432 miles a year is too terrifying to imagine. "Where's Granny today?" "Oh it's her day for fell running." "No, that was yesterday, so it must be decathlon."

The worst thing is that at the end of it all, you're not going to be super-thin. You just won't have put on any more weight. And if you're a fitness freak at 30 and are running 20 miles - shudder. By the time you're 70 you'll be employed as a courier for people needing weekly London to Nottingham deliveries.

Anyone who thinks this is unlikely to be true, think of Diana, Princess of Wales. This is a woman who appears to have dedicated half her life to attending the Chelsea Harbour Club (and not all of it could have been asking men like Christopher Whalley what a girl has to do to get a coffee round here). And think of the recent photographs. The first thing everyone says is "But he's shorter than her". The second thing is "Hasn't she put on weight?" I haven't felt so happy since an aerobics instructor warned that doing stomach exercises wrongly meant you could end up with convex rather than concave stomachs. I've felt free to avoid sit-ups ever since - just in case.

Exercising is neither safe nor healthy. Just think: have you ever heard of anyone suffering from groin strain who wasn't a serious sportsman (or perhaps Peter Stringfellow)? And is it possible to have painful torn ligaments if all you do is sit around and watch television?

No, the health business is just out of control. The logical conclusion is that we will all spend so much time exercising so that we do not have any time to eat and so lose weight.

Even then there are problems. It might seem virtuous to spend your life miserably munching on carrots and baked potatoes. But in May 1995 the Ministry of Agriculture, Fisheries and Food advised people to peel, top and tail their carrots before eating them. It had been discovered that some contained more than 25 times the expected content of organophosphate pesticides.

And acute illness and even death have resulted from eating sprouted green or blighted potatoes because of the alkaloids solanine and chaconine present.

At the same time a recent Health Which report has calculated that swapping a healthy-looking Greek salad with garlic bread for shepherd's pie and broccoli would wipe 429 calories and a massive 39g of fat off your daily intake. Wash it down with a glass of red wine and a bar of chocolate which contain chemicals known as phenols, which prevent the oxidation of low- density lipoproteins ("good" blood fats) into a more dangerous form that clogs up the coronary arteries and you're well on the way to a healthy diet.

So at last the gym instructors, Lycra manufacturers and diet book authors can back off and leave me in peace in front of the television. The next time I'm urged to go and do something healthy I shall simply quote the American educator Robert Hutchins back at them. "Whenever I feel like exercise I lie down until the feeling passes"