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.
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.