The Dukan diet has overtaken the Atkins in terms of popularity this year, with the French doctor's book selling like hot cakes since its launch in the UK in May. With celebrity fans including Jennifer Lopez and supermodel Gisele Bundchen - both of whom credit losing their baby weight to the Dukan plan - and more than two million copies of the book sold in France, it really is the diet everyone's raving about these days.
Well, not quite everyone is raving about it. Experts from the renowned Institut Pasteur in Lille have declared the protein-heavy eating plan as 'unbalanced', along with several other popular diets including Atkins and the Montignac diet.
The diets, say the experts, lead to serious nutritional imbalances, and provide far more protein than is recommended on a daily basis. And those diets that include a virtually carb-free initial phase - including Dukan and Atkins - contain 10 times less daily fibre than official recommendations too.
The researchers also claim that in 95% of cases, slimmers who lose weight on such a diet plan just gain it all back - and sometimes even more - afterwards. Nothing, they say, can replace a balanced, varied diet. In other words, forget about all the faddy eating plans and just eat healthily.
Dr Dukan, meanwhile, has hit back, claiming his work helps fight against the real health risk - obesity.
Whose side are you on?