The British Dietetic Association (BDA) has named the Dukan Diet the worst celebrity weight loss plan of 2013.
The diet, which is said to be a firm favourite with stars including Kate Middleton, Jennifer Lopez and Gisele Bundchen, beat the Party Girl IV Drip Diet and the Alcorexia / Drunkorexia Diet to top the BDA's annual list of the Five Worst Celebrity Diets to Avoid in the New Year.
The Dukan Diet recommends consuming only foods rich in protein which it claims promotes weight loss of 7lb a week.
Despites its popularity, experts at the BDA have branded the diet as "confusing, rigid and ineffective" and said that cutting out entire food groups can do more harm than good.
The leading health group said: "There is little solid science behind this. The diet works on restricting foods, calories and portion control. Cutting out food groups is not advisable.
"This diet is so confusing, time consuming, very rigid and, in our opinion, so very hard to sustain. Even Dukan himself warns of the associated problems like lack of energy, constipation and bad breath. That sounds lovely!!"
Sian Porter, consultant dietician and BDA spokesperson, said: "As much as we all would love it to be the case, there is no magic solution to losing weight and keeping it off long-term.
"Glamorous images of celebrities saturate our daily media in all forms. These celebs have an army of people to help them to keep looking good, which is essential to their livelihood and plenty of money to do whatever they think it takes.
"If you have some weight you need to lose, then do it in a healthy, enjoyable and sustainable way. In the long term this will achieve the results you are after."
IBTimes UK has a closer look at the other diets that made the five worst celebrity diets to avoid in the 2013.