5 July 2011 Last updated at 06:50 ET

The Dukan diet: Four slimmers give their verdict

Dr Pierre Dukan's book has sold more than seven million copies

A court in France has ruled in favour of a nutritionist who described the popular Dukan diet as dangerous. Dr Pierre Dukan had brought a libel case against his rival Dr Jean-Michel Cohen, who had said the protein-rich diet could cause heart disease and breast cancer.

The Dukan diet currently features on non-fiction bestseller lists in both the UK and the US, and was France's best-selling book last year. Well-known devotees range from the Duchess of Cambridge's mother, Carole Middleton, to singer Jennifer Lopez.

The diet begins with an "attack phase" when only protein and oat bran may be eaten. In phase two, non-starchy vegetables can be added every other day. Ultimately, you are allowed to eat normally, but with one protein-only day per week. Exercise is obligatory.

Here four people who have tried it describe their experiences. Below that, the verdict of Dr Elisabeth Weichselbaum of the British Nutrition Foundation.

Can you Dukan diet?
Dee Atta	Hilary Robinson	Camilla Rzewuski	Joel Solon
Marketing, London	Event planner, London	Teacher, Paris	Website designer, London
Weight lost
5kg/11lbs in two weeks	16kg/2st 7lb in 13 months	6kg/13lbs in two weeks - but I've gained it all back since giving up	13kg/2st in one month, and another 6.5kg/1st after that
Side effects
Headache on day two, general loss of energy, bad breath, constipation	None	Dry mouth, bad breath, constipation	No constipation if you drink lots of water and eat oat bran
Protein source
You end up eating breast of chicken, breast of chicken and breast of chicken	I eat a lot more fish than I used to - mainly salmon and prawns	I got totally fed up with crab sticks - I even had them for breakfast	I now make my own sashimi - it's raw salmon, you just need a sharp knife
Too much salt or fat - high cholesterol?
Cholesterol is a concern - which is why Dukan recommends salt-free and fat-free foods, where possible	You can choose to eat too much of these things, or not - and I am careful	This was not a worry for me	I always tend to eat too much salt, but my cholesterol level has gradually gone down while I've been on the diet
Comparison with other diets
Have not tried other diets	I tried Atkins about 10 years ago, but did not get anywhere with it. Also French Women Don't Get Fat - that worked for a while but didn't last	I tried one other, the Montignac diet, which was really good - you can eat everything. I will try that one again.	I have tried to eat less before, but it has left me feeling hungry. With this diet if I feel hungry I just go and eat some raw fish
Would you recommend it?

Dukan Facts

• The Dukan diet tells followers to drink at least 1.5 litres of water per day
• It recommends oat bran on the grounds that it provides fibre, makes you feel full, and may lower cholesterol
• Pierre Dukan told Le Figaro last week that people following his diet should take multivitamins during the first two phases
• Bad breath can result whenever the body burns its own fat, instead of food - Dee Atta says he overcomes this by chewing cardamom pods

Dr Elisabeth Weichselbaum of the British Nutrition Foundation says it is never a good idea to cut out a whole food group from your diet - in this case, starch and carbohydrates.

"If you restrict yourself for a week, you may not really risk your health, but for a longer period of time you will miss out on important nutrients," she says.

The best answer for someone wanting to lose weight is to continue eating a balanced diet, but in sensible quantities.

High-protein diets do lead to weight loss, she says, and cutting out carbohydrates for a short period to kick-start a diet is acceptable.

"But in the long term, if you have anything that's too restrictive you will risk your health."

Diets that are higher in carbohydrates and lower in protein are "generally associated with lower risk", Dr Weichselbaum says. "High-protein" can mean "high-fat", she points out, if people eat fatty meats.

And if "high-protein" means "low-fibre", constipation is very likely to be the result.