The Dukan Diet is a high-protein, low-carbohydrate diet with four phases, each of which has specific rules and food lists. The diet was created by Pierre Dukan, a French physician and nutritionist, and is based on the theory that eating a lot of protein can help people lose weight. The four phases of the diet are:

1. Attack Phase: This phase lasts 2-7 days and involves eating only lean protein, such as chicken, fish, and eggs, along with 1.5 tablespoons of oat bran per day.

2. Cruise Phase: This phase lasts until you reach your goal weight and involves alternating days of lean protein with days of protein and non-starchy vegetables, along with 2 tablespoons of oat bran per day.

3. Consolidation Phase: This phase lasts 5 days for every pound lost and involves gradually reintroducing other foods, such as fruit, whole grains, and cheese, while still eating lean protein and oat bran.

4. Stabilization Phase: This phase is meant to be followed for the rest of your life and involves eating a balanced diet with one day per week of only lean protein and oat bran.

While the Dukan Diet may contribute to weight loss, research has linked it to possible health complications, including kidney disease and liver disease. Additionally, the diet may not provide the full range of nutrients the body needs, and it eliminates many healthy foods. The British Dietetic Association has named the Dukan Diet the number 1 "diet to avoid".