dr. pierre dukan, the inventor of the renowned dukan diet, sued a rival for libel.ere's juju chang. >> reporter: in large part, because one reported devotee was a very slim mother of the bride and not just any bride, this one had the most watched wedding in history. dr. pierre dukan's high-protein diet has hollywood star lets and commoners singing its praises. >> i tried weight watcher. i've tried them all. >> reporter: anna was a serial dieter. this was before, she says, a new diet changed her figure and her life. you look like a different person there. >> i am a different person. you don't know how much more confidence i've got. >> reporter: latest in the bulging pantheon of fad diets. each captures the hopes of people struggling to lose those annoying extra pounds. >> that is okay. that is okay. >> reporter: the diet was launched by this man, dr. pierre dukan, a french nutritionist who traveled across the pond to launch dukan here in america with its promises of quick results and easy rules. too much fat? >> too much fat. >> reporter: but back in france, dr. duka

dr. pierre dukan. author of the dukan diet. it has at kin high mix of protein and oat bran and in this corner diitition. john cohan who said dukan low carb diet is dangerous. dukan is suing for libel after he bad mouthed the diet to a french magazine accusing the media of climbing on the bandwagon of the fantasy. cohen said it is unhealthy but lead toz long-term health problems. >> it is a dangerous diet. you have too much protein and you eat too much fat and you don't have vegetables and you need vitamins and so you have no fiber . you have consteipation and breast problem and sometimes, urges. >> and dukan said there is no truth to the allegation. when followed correctly it is safe and effective method of weet i sat down with dr. dukan. it is not a quick fix. >> quick to lose weight but long to keep it. >> dukan diet works in four faces. encouraging speedy weight loss with lean protein and his special ingredient. oat brain. not rolled oats. but oat bran from the husk. >> it makes you feel full. >> full and fortified. >>> and

dr. pierre dukan, the designer of the popular dukan diet.hout going hungry. and in this corner, dietitian jean michel cohen, another author who says dukan's low-carb diet is dangerous. dukan is suing cohen for libel, accusing the media of climbing on the bandwagon of this fantasy. cohen says the diet is not only unhealthy, it the lead to long-term health problems. >> this is a very dangerous diet because you have too much protein. you eat too much fat, chicken. and you need vitamins. you have no fiber. and you have constipation, breast problem. and sometimes a very frequent heart disease. >> reporter: in a statement, pierre dukan says, there is no truth to the unsubstantiated allegations. when followed correctly, the dukan die set both a safe and effective method of weight loss. i recently sat down with dr. dukan. this is not a quick-fix diet. >> no. it's quick to lose weight. but very long to consolidate. >> reporter: consolidate, that's the key. the dukan die quiet works in four stages. the attack phase starts with encouraging weight loss,