Life and style: Health

We know that diets are inherently flawed, so why do we keep swallowing regimes such as the Dukan?

Have you ever wondered how French women stay so miraculously thin? Me neither. However, given the regularity with which this question now comes up for consideration it may not be an issue we can dodge for much longer. Supposing French women are, indeed, thinner than women from other affluent nations, is it because a) they don't eat too much or b) because so many are followers of the high-protein Dukan diet which promotes itself as "the French medical solution" and "the real reason the French stay thin", catchphrase: "Five million French people can't be wrong"?

You might, pedantically, argue that it has not been unknown, in living memory, for at least five million French people to be less than reliable role models. Even now, the National Front's Marine le Pen remains ahead of Sarkozy in the polls. Again, if French practice provides an irrefutable argument for lifestyle change, we ought, surely, to be emulating their enthusiasm for enemas and nuclear power stations. But in the fat department, Dr Pierre Dukan has, it turns out, made an inspired marketing decision and one that might, in retrospect, help explain the shaky reputation of a fellow protein-gobbler: what does American obesity tell us about the Atkins diet? By declaring his regime the answer to the perennial question about thinness and the French, Dukan has enlisted every non-obese French woman as a testimonial, regardless of whether she has ever been persuaded by his super-scientific approach. "Dear readers, be on your guard," he writes, in the new English edition of his bestseller. "The fight against excess weight has to be carried out by doctors, this is crucial."

Be on your guard, dear readers: Dr Dukan refers to medics of a particular persuasion and not, for example, doctors such as Dr Jean-Michel Cohen, a critic of the Dukan method, whom he is currently suing for libel. Nor does he allude to the doctors working for France's Agence nationale de sécurité sanitaire, which last year included his diet in a list of 14 popular regimes which it alleged – Dr Dukan is very sensitive on this point – are ineffective and potentially dangerous to health. Dr Lecerf, who led the study, was satisfied – pace five million French people – that 95% of dieters regain weight as soon as they stop dieting. "Each regime is less effective than the one before and the weight gain afterwards is greater each time."

The five million French can look after themselves: what of our leading British Dukanians, Carole Middleton and Woman's Hour's Jenni Murray, the latter author of a Dukan diary in the Mail? Are they at risk? We note, at any rate, that Mrs Middleton has yet to pose in the accepted manner of triumphant slimmers, inside the gargantuan, elastic-waisted jeans worn by her obese self, alongside the headline: "I cried when I realised I would not fit through the door of the Abbey". As for her fellow Dukanian, following an inspirational loss of three stone, recent lapses involving chips, chocolate, wine and ice-cream now threaten to make Jenni Murray less the pin-up for protein-fuelled transformation than a reminder of this eternal truth: the diet industry is built on the repeated, utterly predictable and necessary failure of its own products.

The peculiar commercial brilliance of high-protein wheezes is that once any initial, dramatic, carb-starved weight loss has given way to normality, as it must for all but the most lonely or obsessed, and to the gradual regaining of weight and fresh breath, its euphoric adherents will have already invested in the required library of diet book, recipe book, lifelong rule book – none of which can add much to what was said, with far greater modesty and concision, by William Banting in his "Letter on Corpulence", published in 1863. "The great charm and comfort of the system," wrote Banting, after he lost 50 lbs on an eccentric but effective protein diet, "is that its affects [sic] are palpable within a week of trial, which creates a natural stimulus to persevere for a few weeks more, when the fact becomes established beyond question." Or not.

To be fair to Jenni Murray, she is not the only intelligent woman publicly to confess to a private habit some people would find embarrassing. Where weight loss is concerned, the most respectable journalism will suspend scepticism, offer promotional services gratis and, in extreme cases, accommodate claims that would, if made in a South African village, prompt reflections on the stubborn nature of superstition. Who would believe, for example, in singing fat away? Step forward a woman introduced in the latest Elle magazine as the Fat Whisperer. "I talk to the fat," she explains. "And I just tell it to go. I listen to the emotion in the cell membrane and I tell the cell which way to move out of the body." And the cell has to go somewhere, right?

It's easy to be cynical, but how else, other than migrating fat cells, do you explain the plight of people who gain without over-eating? For all we know, Eric Pickles is 90% composed of Whisperer clients such as Kate Hudson and Paris Hilton.

Moreover, from a first do no harm perspective, no one could say of Whispering, as Dr Jean-Michel Cohen has said of Dukan, that it causes "veritable alimentary destruction which leads to serious health problems among certain patients such as a strong rise in cholesterol, cardiovascular problems, breast cancer".

Last week, the libel case came to court. In Cohen's defence, his lawyer has cited a study of 5,000 Dukanians, indicating – allegedly – that 80% of those who followed the diet regained their lost weight in four years. Dukan's lawyer says the figure is 40%. The only reason to doubt the purity of Jean-Michel Cohen's intentions as the enemy of "malbouffe" is his connection with another French diet: "Savoir Maigrir avec Jean-Michel Cohen." For Dukan's part, the great carb-hater is not "seeking profit or fame". He wants, says his lawyer, to bring people "slimming methods capable of bringing them ways of fighting obesity for their whole life".

I am no doctor, but if that is so would not his profits be best dedicated to nutritional education, so women won't fall for regimes like the frankfurter diet recently – and mischievously – awarded the imprimatur of the British Heart Foundation? A BHF dietician explained that a dinner of two frankfurters, half a cup of carrots, a cup of broccoli or cabbage followed by vanilla ice-cream "lacks a number of nutrients we need to stay healthy". How could anyone fall for it? Possibly because it looked so varied after two weeks dining, in the Dukan manner approved by Grazia, Carole and the Daily Mail, on a couple of slices of meat.

Why are French women so thin? From sprinting away from Dominique Strauss-Kahn still has to be the most plausible explanation.