French Dukan Diet Founder Dr. Pierre Dukan is suing diet author Jean-Michel Cohen for libel.

Cohen told French health magazine "Meilleure Sante" that Dukan's high protein and oat bran diet is dangerous.  He also claims that the diet can lead to long-term health problems.

The Dukan Diet has four phases. The only questionable phase is the "Attack phase."

According to the Dukan book you must stay on the attack phase for 3-5days. On the Attack phase you can eat low fat protein such as lean beef and chicken and non-fat milk products. You must have 1.5 tablespoons of oat bran daily and 1.5 liters of water. He also prescribes 20 minutes of daily walking on this phase of the diet.