It has been hailed as the French diet that reportedly helped the Duchess of Cambridge squeeze into her royal wedding frock and enabled the singer Jennifer Lopez to shift her pregnancy pounds. [See footnote]
The protein-rich Dukan diet, which has swept across Europe and the US, has become the weight-loss plan of choice for the rich and famous. They are attracted by the promise of losing up to 15kg (2 stone) in a few weeks by eating as much as they want, as long as it is mostly meat, fish and fat-free cheese.
Fans of the diet are also said to include mother-of-the-bride Carole Middleton and the opera singer Katherine Jenkins. Those who have slimmed to a shadow of their former selves on the diet will not have a word said against it, despite its draconian rules.
It may, however, all be too good to be true. Some have claimed that the diet, invented by the French nutritionist Dr Pierre Dukan, is not only ineffective but can damage dieters' health.
A survey of nearly 5,000 "Dukanians" found that 80% regained all the weight they had lost within three years, and experts who analysed the results of the survey claimed the diet was a public health risk.
Dr Boris Hansel, a metabolism and cardiovascular system specialist at the Pitié-Salpêtrière hospital, in Paris, said: "The diet is not a long-term success because it does not meet our body's needs.
"There are real risks … infertility, sleep apnoea, high blood pressure, type-two diabetes, liver disease or cardiovascular problems. Following this diet is not harmless; it could cause real health problems," he told Le Parisien newspaper.
"Our inquiry is preliminary and shows the need for a real scientific study. The Dukan diet has to be evaluated because it poses a public health problem."
Doctors claim Dukan's latest advice to pregnant women to follow his diet "as early as possible and throughout the pregnancy" put their unborn baby at risk.
Irene Margaritis, spokeswoman for the French food standards authority, said a pregnant woman who dieted risked slowing down the growth of her baby.
She criticised Dukan's recommendation that mothers-to-be eat plenty of oily fish, seafood (including crustaceans) and offal, which is rich in vitamin A, an excess of which can cause malformations.
Dukan, whose 20 books have been published in 14 languages and sold millions of copies around the world, is the biggest selling author in France. He rejected the criticism, saying his diet was normal and healthy, and helped those following it to avoid what he considered the real health risk: being fat.
"We doctors have weighed up the risks and the benefits. I consider that the real risk is an excess of weight and obesity. Every day there are people who die from this and I am trying to fight against it," he told Le Parisien.
He added: "If a mother is obese during her pregnancy she will have a child at risk of diabetes or being overweight."
• This article was amended on 10 February 2012 because it listed model Gisele Bündchen among women reported to have "shed their pregnancy pounds" through using the Dukan diet. A representative for Gisele Bündchen has asked the Guardian to make clear that the model "has never followed this diet, nor has she ever authorised Mr Dukan ... or any media to use her name or image in any way associated with this matter". Gisele Bündchen's name has been deleted from this story.
