What Is the Dukan Diet? Here's What a Dietitian Has to Say

The Dukan Diet may not be as popular as the keto diet or the ProLon diet. But this meal pattern is gaining traction in the weight-loss world, thanks to lofty promises to help people lose weight quickly, making it very appealing for people who need to drop some pounds ASAP. But although the Dukan Diet might be linked to some appealing potential outcomes, it does have some aspects that raise red flags regarding how healthy following it actually is. To learn what the Dukan Diet actually is and whether you should try it out, read on to find out.

What Is the Dukan Diet? And How Does It Work?

French general practitioner Pierre Dukan created the Dukan Diet back in the 1970s. At its core, the Dukan Diet is a low-carbohydrate and low-fat meal plan built around eating primarily lean protein, drinking water and taking a daily walk for about 20 minutes. As with most low-carbohydrate diets, the theory is that the body transitions to burning fat by limiting carb intake.

The Dukan Diet has four phases—attack, cruise, consolidation and stabilization. How long you stay in each phase is based on how much weight you want to lose. Before you start any phase, you calculate your "true" weight by using your age, weight-loss history and other factors. The calculation is made by inputting information on the Dukan Diet website.

Once a person is ready to start the diet, they begin by following the attack phase.

Phase 1: The Attack Phase

The attack phase is intended to jump-start weight loss. During this first phase, participants will eat only lean protein from the allowable protein list the diet provides, along with 1.5 tablespoons of oat bran and a minimum of 6 cups of water per day. During this time, your body is supposed to enter ketosis, similar to other low-carb plans, the idea being that you will use your fat stores as fuel. It is also recommended to include moderate exercise into a participant's day. Typically, that attack phase lasts three to seven days, depending on how much weight a person wants to lose.

Protein foods allowed in this phase include lean meats, fish, eggs, nonfat dairy products and seitan. Small amounts of oil, lemon juice and pickles are permitted. Artificial sweeteners, dietary gelatin and shirataki noodles, low-carb noodles made from glucomannon, can be eaten in unlimited quantities.

Phase 2: The Cruise Phase

Most of the weight loss will come during the second phase of the Dukan Diet, related to the implemented restrictions and guidelines. Transitioning into phase 2 means adding nonstarchy vegetables to the diet in unlimited amounts every other day. Examples of nonstarchy vegetables include zucchini, green beans, eggplant, onions, mushrooms, lettuce, celery and cucumber. Additionally, the plan recommends increasing the oat bran quantity to 2 tablespoons per day. One teaspoon of olive oil to cook vegetables is allowable.

The average length of this phase is based on a schedule of three days for every pound you want to lose and can last several months, depending on your goals. The amount of weight loss that should be achieved should coincide with the "true weight" determined at the beginning of the diet.

Phase 3: Consolidation

This phase is considered a maintenance phase to prevent regaining the lost weight and solidifying the new eating and exercise habits in the diet. Participants start to add back previously restricted foods such as fruit, cheese, whole-grain products like bread and pasta, and celebration "treat" foods and meals in specific quantities. This phase requires that you make one day a week a "pure protein day," essentially meaning that you follow the guidelines for the attack phase once a week. Oat bran and exercise are included in this phase as well.

Phase 4: Stabilization

Stabilization is essentially how a person should eat indefinitely, according to the diet. During this final phase, a person will follow three rules—reserve one day a week for eating pure protein and following the "attack phase" guidelines, eat 3 tablespoons of oat bran per day and walk 20 minutes each day. The consolidation phase should be used as the basis for planning meals during the stabilization phase, helping people avoid eating whatever they please without considering the nutritional content and value. No foods are off-limits, but quantities of foods like fruit are limited.

Certain versions of this diet require people to avoid taking elevators and lean on stairs. People can also reintroduce moderate amounts of alcohol during this final lifetime phase.

Dukan Diet Foods List

The diet's 100 foods list includes lean proteins and vegetables. These foods are permitted in the first phases of the diet. Some foods included on the list are:

Lean Proteins:

• Lean beef such as tenderloin and filet, flank steak and sirloin
• Lean pork such as tenderloin or loin roast
• Chicken and turkey
• Fish such as halibut, cod, salmon, tilapia and tuna
• Low-fat deli meats such as ham and turkey
• Soy products like tofu and tempeh
• Fat-free dairy products like Greek yogurt, cottage cheese and milk

Nonstarchy Vegetables:

• Asparagus
• Beets
• Cabbage
• Cauliflower
• Celery
• Cucumber
• Eggplant
• Fennel
• Green beans
• Kale
• Lettuce
• Mushrooms
• Onions
• Leeks
• Shallot
• Peppers
• Squash
• Spinach
• Tomato
• Zucchini

During these phases, sugar-free gum, sugar substitutes, spices and unsweetened tea and coffee are also allowed.

Does the Dukan Diet Work?

You are likely to lose weight whenever you make drastic changes to your diet, especially when reducing the quantity of food eaten. While this diet may result in people experiencing short-term weight loss, sustained weight loss may not be seen, as is the case with many low-carbohydrate and restrictive diets.

And as with any diet that eliminates or limits many foods, people can risk experiencing nutritional gaps, possibly resulting in vitamin and mineral deficiencies, digestive challenges, fatigue and other undesirable side effects. Plus, any diet that is highly restrictive might not be sustainable or enjoyable to follow. With many restrictive diets, people regain the weight once they stop following the diet.

One study evaluated 51 women who followed the Dukan Diet to assess the foods that people lean on when on their Dukan Diet journey. Results showed that protein intakes were excessive—especially from foods of animal origin—when compared to recommended nutritional standards. Fruit and vegetable intake was extremely low, possibly contributing to the low intakes of nutrients like vitamin C, folate and fiber that were observed. While these women did experience weight loss, the researchers did report "many nutritional abnormalities" when evaluating the participants. They caution that "adopting this diet in the long-term may pose health threats through acquiring kidney and liver disease, osteoporosis and cardiovascular disease."

Although rare, there have been reports of people experiencing nausea and vomiting due to developing ketoacidosis when following the Dukan Diet.

If a person chooses to follow the Dukan Diet, they should only do so under the guidance of their health care provider or a dietitian. And especially during the first two phases of the diet, a person may experience constipation, fatigue and even bad breath, due to the lack of fiber and carbs their body is receiving.

The Bottom Line

The Dukan Diet has been followed for decades thanks to the weight loss that people might experience in the short term. And while it is true that weight loss will likely be experienced when eliminating entire food groups, people may increase their risk of experiencing other unsavory side effects when they are adopting this eating pattern.

For a person who needs to experience rapid weight loss, this diet is an option that could be explored under the advice of a health care provider or dietitian, especially if the person does not have any underlying health concerns like heart disease or diabetes. But for a person who wants to eat in a way that supports their overall health, more balanced and sustainable diets like the Mediterranean Diet may be a better match for long-term health benefits and lasting weight loss.