The Dukan Diet

The Dukan Diet has been hugely popular in France. Devised by French medical doctor Dr Pierre Dukan, it promises to help you lose weight permanently. But does it really work? DietDoc takes a closer look.

I was recently asked to review 3 books that explain the principles of popular slimming diets. The first in this series, is The Dukan Diet by Dr Pierre Dukan, which is advertised as "The French medical solution for permanent weight loss". Dr Dukan writes competently and convincingly and his book is easy to read.

The basic principles expounded in this book are based on the Atkins Diet, with certain modifications as explained below. Dr Dukan divides his diet into 4 phases, which he calls the Attack Phase, the Cruise Phase, the Consolidation Phase and the Stabilisation Phase. Let’s see what each phase entails.

The Attack Phase

This initial phase is relatively short and drastic. Patients who want to lose weight are instructed to eat only certain protein foods for a period of 1 to 10 days, or 5 days on average.

The following foods are allowed:

  • Lean meats like beef and veal, grilled or roasted without fat
  • Offal such as liver, kidneys
  • All poultry, except duck and goose, without any skin
  • All fish and shellfish
  • Eggs
  • Fat-free dairy products like yoghurt or milk

(Dukan, 2010)

In addition Dukan Diet users are encouraged to drink lots of water, reduce their salt intake and have 1 ½ teaspoons of oat bran a day.

Dr Dukan also stresses the importance of doing exercise every day.

During the Attack Phase, patients tend to lose a large amount of weight very rapidly, which, as Dr Dukan rightly points out, is highly encouraging to most slimmers.

The Cruise Phase

The second step of the Dukan Diet is called "The Cruise Phase" and consists of 1 day of Attack Phase eating alternated with 1 day of eating lean protein and certain selected vegetables. The latter are mainly vegetables with a very low carbohydrate content such as lettuce, cucumber, spinach, etc. (i.e. the so-called "negative energy" vegetables). Dieters are encouraged to continue drinking plenty of water, use oat bran on a daily basis and do exercise (Dukan, 2010).

Dr Dukan stresses that this second phase of his diet regimen is the most important and should be followed until the person using it has reached his/her desired goal or true weight. Considering that Dr Dukan predicts an average loss of 0,5 kg every 5 days, the Cruise Phase could last for rather long in the case of patients who need to lose 20 or more kg.

The Consolidation Phase

This phase, which Dr Dukan also calls the "crucial Transition Period", allows the addition of one fruit, 2 slices of wholewheat bread and 1 serving of cheese per day, plus 2 servings of starchy foods and 2 so-called celebration meals (eating any foods desired in moderate quantities) per week. 

The length of the Consolidation Phase is calculated according to the amount of weight a dieter has lost during the previous 2 phases, e.g. 5 days for every 0,5 kg or 10 days per 1 kg lost (Dukan, 2010). Thus someone who has lost 20 kg in Phases 1 and 2, would have to stay in the Transition Phase for 20 x 10 = 200 days or nearly 7 months.

The Stabilisation Phase

At this point, dieters will have reached their true or goal weight and will have adapted to the high-protein and selected vegetable diet and are including some fruit, starches and the occasional treat. In the final phase, Dr Dukan advises that individuals who have completed the previous 3 phases of the diet, can return to normal eating, but should reserve one day a week , namely the famous "Protein Thursdays" on which they eat only Attack Phase foods (i.e pure proteins). 

Dr Dukan prescribes three simple rules of this final phase: Protein Thursdays, taking 3 tablespoons of oat bran for the rest of one’s life and doing daily exercise (Dukan, 2010).

Will this diet work?

Dr Dukan writes very persuasively and many people who have tried and failed to lose weight in the past will probably use his diet with varying degrees of success. I can imagine that most dieters will definitely lose weight during the 1-7 day Attack Phase because research indicates that eating only lean proteins tends to suppress the appetite due to ketosis, improve satiety, prevent cravings and cause a diuretic effect (LaRosa et al, 1980). Patients would also only use the Attack Phase for a very short period of time, which in most cases should not lead to serious negative side-effects.

However, I doubt that most individuals would be able to stick out the Cruise and Transition Phases which could last for months on end depending on how much weight the person has to lose. Ask yourself if you could eat (and afford) only protein, a few selected vegetables and a small portion of oat bran for a long period during the Cruise Phase. 

And afterwards, could you eat the restricted diet of the Transition Phase for months and months? 

Research studies have indicated that the fall-out rate for high-protein diets is very high because people tend to get very tired of eating only proteins and a few vegetables (Foster et al, 2003; Stern et al, 2004). As omnivores (not carnivores), humans tend to need a varied diet which also includes carbohydrates.

The ADSA position  

I have previously referred to the position of the Association for Dietetics in SA (ADSA) in regard to high-protein or any other diet that cuts out whole food groups or concentrates on only a few selected foods. As a member of ADSA, I can also not recommend that anyone should eat only proteins (even if they are low-fat and if some do contain calcium - improvements on the original Atkins Diet) and ‘negative energy’ vegetables for long periods of time. This type of diet may help you lose a lot of weight very rapidly at the beginning, but its sustainability over time is questionable.

The first and most important Food-Based Dietary Guideline for South Africans is "Eat a variety of foods". Because the Dukan Diet does not subscribe to this guideline, I cannot recommend it and would urge Readers to rather use a well balanced, low-fat diet with a reduced energy content and daily aerobic exercise to lose weight sensibly without sacrificing dietary variety.

 - (Dr IV van Heerden, DietDoc)

Any questions? Ask DietDoc                                                 


(Dukan, P (2010). The Dukan Diet. Hodder & Stoughton, UK; Foster GD et al (2003). A randomized trial of a low-carbohydrate diet for obesity. New Eng J Med, 348(21):2082-90; LaRosa JC et al (1980). Effects of high-protein, low carbohydrate dieting on plasma lipoproteins and body weight. J Am Diet Assoc, 77:264-270; Stern L et al (2004). The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomised trial. Annals of Int Med, 140(10):778-85.)

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