"I feel fantastic absolutely fantastic, I go out shopping now and i buy size 10 clothes and I just feel wonderful." Says Isabel

"It's so tasty and easy you don't want to break it at all, it's not a healthy diet and it's not a sustainable diet." Says Kerry

Try telling that to the 10 million worldwide devotees of the Dukan Diet made famous by Jennifer Lopez and more recently Kate Middleton...Its been a year since it hit our shores and today its transformed the lives of nearly 70,000 Australians the book is still one of our best sellers and its our most popular diet.

"My waist, my stomach, my thighs they've halved, they've halved in size, its just amazing." Says Isabel

At 48 Isabel Coulson is ecstatic at her weight loss after failing at many other diets she's finally experienced success on the dukan diet she's been on it for 6 months.

"I started the diet on Jan 11 and within 4 months id lost 13.5 kilos, my goal was to lose 12.6 but i actually went up to 13.5 kilos I can now fit into size 10 clothing which before I was fitting into a size 14 to 16." Says Isabel

Kate Middleton's dramatic weight loss is attributed to the diet. Her latest appearance has sparked concerns that the new Duchess of Cambridge has lost too much but for another devotee of the diet Kerry Kitson Kate's a shining example of the success you can achieve

"So I've gone from a size 14 to a baggy size 12 now. So I need to go out and buy some size 10s now which is wonderful." Says Kerry

The diet designed by a French Dr is split into four phases the first attack phase is also the hardest protein rich foods only for five days. The second cruising phase allows vegetables dieters stick to this until they hit their goal weight.

"The weight comes off really quickly which is really motivating and then you go on to the consolidation phase and I've just managed to keep it off." Says Kerry

The third consolidation phase introduces fruit, cheese and starchy foods and two free choice meals a week...this lasts 10 days for every kilo lost the stabilisation fourth phase encourages healthy eating with one protein only day a week.

"The thing I love about it is that you never have to be hungry I never really thought that I ate a lot but if I did try a diet I was always really hungry." Says Kerry

"It really promotes yo yo dieting and it creates yo yo dieting because you really do feel great after you've lost weight, everyone will try the Dukan diet because they know it's successful." Says Arlene

Dietician Arlene Normand advises her clients to steer clear of the Dukan Diet and instead follow a simple balanced diet with smaller portions.

"Cutting out a lot of fruit, vegs, whole grains is not a balanced diet so i really wouldn't suggest people go on this, and if you dont go on it long term how are you going to sustain your weight long term." Says Arlene

But Isabel disagrees "It's been super easy I'm now six months since I started the diet and I'm finding it very easy to maintain very easy."