It is a high-protein diet in which both fats and carbohydrates are restricted. This is unlike the Atkins Diet and other low-carbohydrate:high-fat (LCHF) diets, in which fat is not restricted.
The diet consists of four phases designed to aid fast weight loss and ultimately, weight maintenance. The diet's first two phases are based on a list of 72 to 100 permitted foods to promote rapid, consistent weight loss. The final two phases involve re-introduction of foods with an aim to help dieters keep the weight off permanently.
There is no calorie restriction and you are allowed to eat as much of the allowed foods as you like. For every stage of the diet, you are required to eat a limited portion of oat bran daily.
The four phases of the Dukan Diet
- Attack Phase - this phase can last up to 10 days depending on how much weight you have to lose. During this phase, dieters can expect to lose the most weight in a short amount of time. This helps with motivation and to continue with the diet.
- Cruise Phase - this is the longest phase of the diet. The aim is for steady, gradual weight loss of around 2 lbs per week, using a combination of 'Pure Protein' days and 'Protein and Vegetable' days from the list of permitted foods. This phase continues until you have reached your weight loss goal.
- Consolidation Phase - In this phase, you are entitled to a list of 100 unlimited foods. Small amounts of higher-calorie foods and celebration meals are also allowed. Other food groups are gradually re-introduced including strictly controlled portions of starchy carbohydrates and fruits. You are required to eat only 'Pure Proteins' one day per week, which claims to keep your weight stable.
- Stabilisation Phase - this phase allows you to eat as you wish, as long as you are following three rules for life. This includes:
- Walking for 20 minutes every day and avoiding lifts or escalators.
- Including one 'Pure Protein' day every week.
- Including three tablespoons of oat bran every day.
What can I eat on the diet?
The diet is based around 72 to 100 permitted foods which are high-protein, low-carbohydrate and low-fat. The permitted foods vary depending on what phase of the diet you are on. Foods allowed include:
- Lean meat such as chicken, turkey, lean beef, lean ham, and veal.
- All fish and shellfish including trout, cod, mackerel, salmon, haddock, prawns, mussels, clams and squid.
- Fat-free yoghurt and fromage frais (as long as it does not contain fruit), quark, fat-free/low-fat cottage cheese and skimmed milk.
- Certain vegetables during the 'Cruise Phase', including celery, peppers, asparagus, mushrooms and broccoli, but other vegetables such as carrots, sweet potatoes and sweetcorn are not allowed.
How does the Dukan Diet work?
There are a number of claims as to why the Dukan Diet works.
- Protein is low in calories. It contains only 4 calories per gram compared to fat, which has 9 calories per gram. Therefore, you are less likely to meet your daily energy needs from foods high in protein and low in fat.
- Protein makes you feel full and satisfied, which helps you to eat less. A number of studies have provided good evidence that protein has a filling (satiating) effect leading to weight loss.
- There is convincing evidence showing that protein increases 'thermogenesis', which is the production of heat within the body. In other words, it takes more energy to metabolise protein; therefore, you are burning more calories eating protein than you would by eating fat or carbohydrates.
- By restricting carbohydrates and fats, the diet mimics a state of starvation within the body. This forces the body to use fat stores as a source of energy.
What are the pros (benefits) of following the Dukan Diet?
- Losing a lot of weight in the initial stages of the diet is highly motivating. This encourages people to carry on with the diet.
- Having a list of 'allowed' and 'not allowed' foods makes it easy to follow and understand.
- There is no restriction on how much you are allowed to eat, and protein satisfies hunger. This means you are less likely to feel hungry on the diet.
- The diet is restrictive, and therefore you are cutting out foods that are high in sugar and fat which are linked to weight gain and obesity.
- There are support groups, coaching and recipes that can be found online and on internet forums, which can help with encouragement and to reduce boredom with the diet.
What are the cons (disadvantages) of following the Dukan Diet?
- The initial loss of weight is mostly water. When carbohydrates are cut from your diet, the body uses a stored source of energy in the liver and muscle, known as glycogen. Each gram of glycogen is bound to around 3 grams of water, which is lost from the body. This is why you see a considerable decrease in weight on the scales.
- Evidence shows that no more weight is lost following a high-protein, low-carbohydrate diet in the long term compared to other diets providing all food groups. In fact, some studies have shown that eating a diet with carbohydrates, fats and proteins results in a larger percentage of fat loss. High-protein, low-carbohydrate diets result in a larger percentage of weight loss coming from water, at least initially.
- The diet is based on higher-priced food items such as meat, fish and oat bran so can be an expensive way to lose weight.
- The diet is very restrictive which can lead to boredom and poor compliance with the diet.
- There can be unpleasant side-effects of the diet, including headache, feeling sick (nausea), constipation, bad breath and extreme tiredness (fatigue).
- There has not been enough research to confirm the safety of following the Dukan Diet. Some concerns have been raised that low-carbohydrate, high-protein diets can lead to a build-up of ketones in the body. Ketones are produced if your body is forced to break down fat for energy. This can affect the way important chemicals (hormones) are metabolised, including insulin. This, with the addition of excessive protein consumption could ultimately impair the function of the liver and kidneys. However, more research is needed.
- The diet is very limited, which can lead to nutrient deficiencies. The diet discourages foods that are known to promote good health and well-being, whilst protecting against disease and illness. This includes nuts, seeds, fruit, some vegetables, beans, pulses and whole grains, all of which contain vital vitamins and minerals.
Should I follow the Dukan Diet?
The Dukan Diet may help you to lose weight quickly, but it does not go without risks. The Dukan Diet is a high-protein, low-carbohydrate diet, which does not seem to result in any more weight loss than a diet that adopts healthy eating principles. In the final stage of the diet, you are advised to eat how you like, which could result in returning to unhealthy eating habits. This usually ends up with weight being regained.
Ultimately, a diet that is as restrictive as the Dukan Diet will result in weight loss simply due to a calorie deficit as a result of limited food choices, boredom and lack of enjoyment from eating. Weight loss can be more effective by making realistic changes that you can stick to for life, meaning that food can be enjoyed and no foods are off the menu.
The Dukan Diet does not educate those following the diet on the healthy eating behaviours that are key for long-term weight loss and overall health. A diet that is well balanced will be more likely to:
- Be one you will be able to keep to (sustain).
- Be enjoyable.
- Provide you with all the nutrients necessary for long-term health.
A well-balanced, healthy diet is based on fruit, vegetables, whole grains, fish and nuts, plus small amounts of meat, dairy and unsaturated fats. This is backed up by extensive research and evidence, as opposed to the Dukan Diet which lacks evidence to confirm the long-term safety and effectiveness of the diet.
Further reading and references
Obesity; NICE CKS, June 2015 (UK access only)
Weight management before, during and after pregnancy; NICE Public Health Guideline (July 2010)
Hafekost K, Lawrence D, Mitrou F, et al; Tackling overweight and obesity: does the public health message match the science? BMC Med. 2013 Feb 1811:41. doi: 10.1186/1741-7015-11-41.
Guasch-Ferre M, Babio N, Martinez-Gonzalez MA, et al; Dietary fat intake and risk of cardiovascular disease and all-cause mortality in a population at high risk of cardiovascular disease. Am J Clin Nutr. 2015 Dec102(6):1563-73. doi: 10.3945/ajcn.115.116046. Epub 2015 Nov 11.
Noakes TD, Windt J; Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review. Br J Sports Med. 2017 Jan51(2):133-139. doi: 10.1136/bjsports-2016-096491.
Harvie MN, Pegington M, Mattson MP, et al; The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes (Lond). 2011 May35(5):714-27. doi: 10.1038/ijo.2010.171. Epub 2010 Oct 5.
Johnston BC, Kanters S, Bandayrel K, et al; Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA. 2014 Sep 3312(9):923-33. doi: 10.1001/jama.2014.10397.
Hooper L, Abdelhamid A, Bunn D, et al; Effects of total fat intake on body weight. Cochrane Database Syst Rev. 2015 Aug 7(8):CD011834. doi: 10.1002/14651858.CD011834.
Osterdahl M, Kocturk T, Koochek A, et al; Effects of a short-term intervention with a paleolithic diet in healthy volunteers. Eur J Clin Nutr. 2008 May62(5):682-5. Epub 2007 May 16.
Obese, overweight with risk factors: liraglutide (Saxenda); NICE Evidence Summary (June 2017)
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