Dukan is suing Jean-Michel Cohen for €15,000 over the allegations made in a French health magazine in 2010, according to press reports.
Dukan’s protein-centric, non calorie-counting diet has won a number of celebrity adherents including the new wife of Britain’s Prince William, Kate Middleton, and Jennifer Lopez, but Cohen slammed it.
He called the diet plan a, "veritable alimentary destruction which leads to serious health problems among certain patients such as a strong rise in cholesterol, cardiovascular problems, breast cancer".
Dukan’s legal counsel told the Paris court hearing the case that Dukan, author of 20 books, sought neither, “profit or fame" rather to promote, "slimming methods capable of bringing them ways of fighting obesity for their whole life.”
Cohen’ counsel called the diet a, "reverse fairy tale".
Both parties submitted surveys reflecting the success of the diet with Cohen’s camp suggesting 80% of those on the diet regained weight after four years. Dukan said the fail rate was closer to 40%.
In 2010 the French Food Safety Agency (ANSES) concluded diets like the low-carb Atkins and high-protein Dukan diet were linked to heart disease and cancer.
Dukan told the French press: "I consider that the real risk is being overweight and obese. Every day, people are dying of that and I am fighting against it. The food that I prescribe is nutrition that I consider to be rigorously normal, healthy and which prevents an excessive weight gain."
The case is due to be resolved on July 5.