Shaun Ward MSc ANutr
What Is The Dukan Diet?
The Dukan Diet is a low-carbohydrate, protein-based diet created by Pierre Dukan – a French medical doctor. Many aspects of the diet seem to originate from other similar diets such as the Atkins diet and the Ketogenic diet.
Although it had been promoted for many years previous, its popularity increased substantially in 2000 when an official diet book was released, The Dukan Diet. The book was a huge success and sold over 7 million copies.
The main selling point of the Dukan Diet is its claims for rapid, permanent weight loss without any hunger. This selling point was the crucial driver behind its great success.
Specifically, the diet consists of a list of over 100 ‘allowed’ foods, as well as 4 specific dietary phases each with their own unique goal; Attack, Cruise, Consolidation, and Stabilization.
The Diet Was Quickly Labelled Unhealthy
Shortly after its release, the Dukan diet was named as one of the five worst diets of 2011 by the British Dietetic Association.
The National Agency for Food, Environmental, and Work Health Safety in France have also declared the diet as “unhealthy” and do not recommend its use in any population.
How Does The Dukan Diet Work?
Below we've detailed the four difference phases the program has:
Phase 1 - ATTACK
This phase is designed to initiate rapid weight loss. The goal is to lose 2-8lbs within a week, although this phase can be maintained longer if users are starting at a high bodyweight.
Individuals are only allowed to consume foods from a list of 68 high protein-containing foods. On top of this, 2.5 tablespoons of oat bran should be consumed per day, as well as completing 20 minutes of physical activity a day.
Phase 2 – CRUISE
This phase is meant to take you to your ideal weight after the more extreme attack phase has been completed. The expected weight loss is slightly less than the first phase, at 1lb every 3 days, but is aimed to be more consistent as the weeks progress.
The cruise phase allows 32 vegetables to be consumed every other day on top of the protein-containing foods. Therefore, users will alternate between pure protein days, and protein plus vegetables days. In addition, 2 tablespoons of oat bran, and 30 minutes of physical activity are recommended each day. 
Phase 3 - CONSOLIDATION
This phase is started when the target weight has been reached and is aimed at avoiding weight regain. The length of this phase depends on the time spent in the cruise phase - 5 days for every pound lost in the cruise phase.
To achieve this, there is a gradual return of previously forbidden foods in small quantities, whilst also allowing for up to 2 cheat meals per week. The restricted foods that can be reintroduced are fruit, starches, whole grain bread, and cheese. However, a pure protein day such as seen in the attack Phase is still scheduled for every Thursday. In addition, 2.5 tablespoons of oat bran, and 25 minutes of physical activity are recommended each day.
Phase 4 - STABILIZATION
This phase is meant to be followed for the rest of someone’s life. It assumes individuals have learned how to eat healthier in the previous phases and can now develop a more sustainable eating pattern to follow whilst including all types of food groups. This phase states that in order to keep the new bodyweight, there are 3 simple but non-negotiable rules:
- 3 tablespoons of oat bran per day
- Walk 20 minutes daily and choose to take the stairs whenever possible
- Have a pure protein Thursday i.e. attack phase menu.
Are There Any Negative Aspects To The Diet?
Below we've broken down the popular criticism of the diet:
It Is Very Restrictive
Despite there being limited quality research analyzing the Dukan Diet, it does not take long to notice that it will not meet nutritional needs and cannot be defined as a balanced diet.
One of the main reasons for this is because unlike other high-protein diets, the Dukan diet heavily restricts both carbohydrates and fat – usually the intake of one of these other macronutrients remains high or at least moderate.
Low-carbohydrate, and low-fat diets, have been proven to be healthy dietary approaches when practiced correctly, however low intakes of both these nutrients at the same time has never been deemed a healthy dietary approach.
For this reason, current evidence indicates that energy intake on the Dukan diet is very low, achieving just ~50% of an individual’s energy needs per day .
In fact, individuals on the the attack phase of the diet have shown to consume under 1000kcal per day, which officially makes the Dukan diet a ‘crash’ diet. Not ideal for a diet that markets itself as a “diet for life”!
The major issues with this low energy intake are that it will cause great losses in lean body mass and have a negative influence on maintaining hormone levels.
Crash diets are also associated with an elevation of cortisol that may cause suppressed immunity, hypertension, skin issues, and muscle weakness .
But aside from crash dieting being physically detrimental, they are also psychologically damaging.
It is documented that extreme diets can have negative emotional consequences such as depression, anxiety, decreased self-esteem, nervousness, and irritability .
Crash diets are even linked with a form of temporary hair loss – Telogen Effluvium – due to the large increases in mental stress .
There have even been cases of severe mental disturbances after rapid self-induced weight reduction that have resulted in hospitalization .
Clearly a less severe reduction in energy intake would still be able to stimulate fat loss but at a more sustainable rate without the extreme side effects seen with crash diets. In terms of fat loss, slow and steady will always win the race.
Another issue with diets that create such a large reduction in food intake is that it becomes increasingly hard to reach micronutrient requirements per day.
It is possible to avoid this if individuals consume high amounts of green leafy vegetables and supplement with various vitamins and minerals, however unfortunately the attack phase of the diet has people eliminate vegetables from the diet. This puts everyone at a very high chance of health issues.
Following the diet for just 8-10 weeks has found to produce nutritional abnormalities, especially regarding water-soluble vitamins (B and C) which need to be consumed in adequate amounts every day as they are not able to be stored for long-term use .
In particular, vitamin B deficiencies are closely linked to weakness, heart palpitations, and nerve problems, whilst vitamin C deficiency may result in internal bleeding, impaired wound healing, and fatigue.
Low in Dietary Fiber
The initial stages of the Dukan Diet are also low in dietary fiber, as this is found only in plant-based foods. It seems Pierre Dukan tried to counteract the lack of vegetables on the diet by using a mandatory serving of oat bran each day, however these servings (1.5-2 tablespoons; 9–12 grams) contain less than 5 grams of fiber.
Compare this to the dietary recommendations of 30 grams of dietary fiber per day and the major issues become apparent.
Dietary fiber is critical for modulating the digestion and absorption of food, is largely responsible for the bacterial composition of the gut, and plays a role in preventing diseases such as type 2 diabetes, cardiovascular disease and colon cancer .
Potential Issues with High Protein Intake
A high-protein diet is not as larger concern as once speculated, and can still be part of an overall healthy balanced diet.
However, when high-protein is combined with diets lacking micronutrients such as ‘crash’ diets, especially those lacking vitamin B groups, then this creates an inadequacy to efficiently metabolize homocysteine - a sulphur containing amino acid produced by methionine metabolism that is abundant in animal products .
Elevated homocysteine concentrations are commonly linked with osteoporosis and atherosclerosis and therefore are another potential health concern on an eating plan such as the Dukan diet which causes B vitamin deficiencies.
Is the Dukan Diet Sustainable?
There is no data to determine whether the Dukan diet is sustained by those that choose to follow it, however given the large body of research on crash diets it is assumed it is not a diet that can be followed in the long-term.
For diets to be successful there has to be an adequate amount of flexibility in most cases to help reduce psychological distress .
However, the highly restrictive nature of the Dukan diet, along with its complicated rules, make it near impossible for anyone to easily follow.
The evidence is clear in showing that very low energy diets such as this end up causing greater weight gain at the end of the weight loss period than the amount lost during weight loss .
Although the high protein intake may help to suppress the large alterations in hormones regulating hunger , the very low energy intake will eventually cause a large increase in appetite that individuals will have to comply with in order to avoid psychological issues. After all, the body is not designed to be starving for endless periods of time.
The Dukan Diet is a low-carbohydrate, protein-based diet created by Pierre Dukan – a French medical doctor.
It is split into 4 separate diet phases, with the first 2 phases designed to severely restrict energy intake and cause dramatic reductions in bodyweight by eliminating the consumption of most food groups.
This diet is clearly a form of ‘crash’ dieting, with caloric intakes shown to drop below 1000 calories in the early stages.
Such large restrictions will inevitably cause significant losses in lean body mass, hormonal issues, psychological disturbances, and micronutrient deficiencies.
A dietary approach such as this is also not sustainable in the long-term, even for the most strong-minded of us, and should be avoided at all costs.