What is the Dukan diet?

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How does the Dukan diet work?

Like similar low-carb plans, the diet mimics the process of starvation by focusing on the consumption of protein with some fat, while omitting carbohydrates. This encourages the body to turn to glycogen stores (carbs) for energy, once these are exhausted (after about 3-4 days) the body switches from burning carbs for energy to burning fat. It does this by turning stored fat into compounds called ketones – this process is called ‘ketosis’.

How to follow the Dukan diet

There are four phases to the Dukan diet, two phases focus on weight loss and two phases support your weight maintenance. How long people stay on the diet depends on their current weight, fitness and desired goal weight. More details for each of the phases can be found on the Dukan website.

1. Attack phase

The duration of this first stage depends on your age, the weight you have to lose and how many diets you have done in the past. Although, on average you can expect it to last between two to five days. Dieters have 68 natural protein foods to choose from, along-with just 1½ tablespoons of oat bran, followers are also encouraged to drink at least six glasses of water.

2. Cruise phase

While pure protein days are still encouraged, carbohydrates are slowly reintroduced in the form of 32 approved non-starchy vegetables. These are enjoyed on PV days (protein and vegetable days). Weight loss in this phase is more gradual at about 1lb (0.45kg) every three days, followers stay in this stage until they have reached their ‘true weight’.

3. Consolidation phase

This phase marks the end of the weight loss phases, the 100 permitted foods remain along-with the gradual re-introduction of starchier, previously forbidden foods, such as fruit and dairy. Followers are even granted up to two ‘celebration meals’ a week where they are allowed to eat almost anything they like (some restrictions still apply).

4. Stabilisation phase

If you’ve managed to reintroduce carbohydrates back into your life without putting weight back on, you can move into stage four and unlock the ‘rules for life’ such as consuming oat bran daily and keeping active. You’ll also start ‘Protein Thursday,’ – on this day you eat just as you would have done during the attack phase; it is this strategy that the diet claims is your insurance policy to maintaining your weight loss.

What foods to eat on the Dukan diet

This depends on which phase of the programme you are in. The early phases of the diet are prescriptive with the 'attack' phase permitting 68 high protein foods only – these include lean meats, poultry, fish, shellfish, plant proteins like soy, as well as eggs and fat-free dairy.

As you progress through the plan, additional foods may be added, for example in the 'cruise' phase you can add 32 non-starchy vegetables. These include the likes of asparagus, squash, tomatoes and mushrooms.

What foods to avoid on the Dukan diet

During the weight loss phases of the plan ('attack' and 'cruise') any foods not on the permitted food lists are avoided. As you progress through the later phases there is a gradual addition of starchier foods, starting with vegetables.

What is Dukan Diet 2?

Since the development of the original diet, a second programme has been formulated. Dukan 2 involves seven steps on a ‘nutritional staircase’– each step represents the dietary inclusion of a food group. Steps one and two involve eating unlimited quantities of the 100 allowed foods, which include natural proteins and vegetables. Subsequent steps involve the graduated addition of fruit, breads, cheese and other starches, such as pasta.

The goal of the ‘nutritional staircase’ is that you lose weight at your own speed within a more relaxed framework.

What’s the evidence for the Dukan diet?

Studies suggest that an average weight loss of about 15 kilograms may be achieved after 8-10 weeks of following the diet. However, along with this comes a number of nutritional abnormalities including high levels of iron and potassium as well as vitamins A and D and low levels of vitamins C and folate.

Is the Dukan diet healthy? Our nutritionist’s view …

Unlike Atkins, the Dukan diet restricts fat and omits vegetables completely in the short ‘attack’ phase, with a gradual re-introduction of some fruit, veg and carbs in the subsequent phases of the diet. It is thought that the 'stabilisation' phase – the last of the four phases – is the one that causes the most problems. That’s because it’s hard to re-introduce a wider selection of food, without putting weight back on, and many followers find it difficult to stick to the weekly 'Protein Thursday'.

There is limited scientific support for the efficacy of the Dukan diet, so although you can expect to lose weight in the initial very strict phases of the diet, many followers go on to regain the weight they originally lost. Furthermore, the nutritional anomalies of the diet suggests that in the long-term, this eating style may pose health risks for the kidneys, liver, bones and cardiovascular system.

Unsurprisingly, Dukan’s weight loss plan has come under criticism from health professionals, many believing that the diet promotes an unbalanced way of eating. In recent years, Pierre Dukan’s controversial claims have also brought unwanted attention upon the Dukan brand. More importantly, though, the diet ignores key healthy eating principles – including the importance of fruit and veg, the benefits of wholegrains and fibre and the health benefits achieved by selecting from a variety of food groups. For these reasons, the diet is likely to be nutritionally imbalanced. It may be argued that Dukan Diet 2 attempts to address these issues by introducing a wider inclusion of food groups. As a result, weight loss is said to be slower and more gradual, requiring a longer-term commitment.

Does the Dukan diet work?

During the initial, very restrictive phase you can expect to lose weight relatively quickly, this can of course be a great motivator. The diet appears attractive for those who don’t like counting calories and prefer a more prescriptive way of eating, because it sets out exactly what you can eat. In the longer term, however, as you revert to a more balanced, healthy diet you may regain much of the weight you lost.

Who shouldn’t follow the Dukan diet?

Diabetics, especially type 1 diabetics, are at risk of complications if they attempt to follow a strict low-carb diet. For this reason, diabetics and anyone with a blood sugar management issue should discuss the potential implications with their GP and healthcare team before embarking on such a regime. Similarly, anyone who meets one of these criteria:

• has a kidney and / or liver disease or a family history of such;
• is under 18 years old or elderly;
• has a pre-existing medical condition;
• is pregnant or breastfeeding;
• has or is recovering from an eating disorder
• or is on prescribed medication including (but not restricted to) insulin, oral diabetic medication or diuretics.

It’s also important to look out for a condition called ketoacidosis. Although rare, it may occur when following a low-carb, high-protein diet. This is when there is insufficient insulin in the blood and as a result ketones are produced too quickly.

Please note, if you are considering attempting any form of diet please consult your GP first to ensure you can do so without risk to health.

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This article was last reviewed on 31 October 2023 by Kerry Torrens.

A nutritionist (MBANT) Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food magazine. Kerry is a member of the The Royal Society of Medicine, Complementary and Natural Healthcare Council (CNHC), British Association for Applied Nutrition and Nutritional Therapy (BANT).

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