Most diseases have something to do with lifestyle and the environment, but the experts in our community, the doctors, know very little about such things. As they only get about one hour's teaching on nutrition in their five years of medical training, this is probably not so surprising.

So when overweight and obese people come to them for advice, the doctor is instead likely to revert to pill-pushing type and reach for the prescription pad.  As a result the anti-obesity drugs orlistat (Xenical) and sibutramine (Reductil) have recently become the most prescribed drugs on the UK's National Health Service, with more than 1 million prescriptions written every year.

The drugs are supposed to be used only when dieting and exercise have failed, but, as Alan Maryon-Davis, president of the Faculty of Public Health, has said: "My fear is that these drugs of last resort are actually used quite early on.  It is too easy to turn to the prescription pad."

But is this really helping the patient?  Despite the enormous commercial success of orlistat, it doesn't seem to.  The drug has lived off early glories for the longest time.  One of the very first trials found that a third of participants lost 10 per cent of their initial weight, a result that had newspapers such as the Daily Mail claiming this was the magic bullet cure for obesity. 

Since then, researchers have conducted 30 further trials on the drug, and have never been able to replicate that early result.  A review of 30 trials into orlistat and other weight-loss drugs found that it achieves an average weight loss of just 2.9 kg a year.

The drugs can also increase the risk of heart disease, and orlistat is especially likely to cause gastro-intestinal problems and faecal incontinence, which the manufacturer has delicately described as "the ooops factor."

The World Health Authority says that "eating less and exercising more must remain the cornerstones of managing obesity."

Just don't go to the doctor if you want to find out how.