Similar to Atkins, Dukan promotes a very-low-carb diet. And as with Atkins, there are four phases: induction, ongoing weight loss, pre-maintenance, and lifetime maintenance (though Dukan gives different names to these phases). And like Atkins, his diet is so popular, that it is impossible to ignore it, or consider it a mere “fad.” For the benefit of Amazon customers, I highlight what is new and different about Dukan. The following is quoted from my book Maimonides and Metabolism”Phase 1: Induction (Attack). Average length is five days. Zero caloric carbs. Unlike Atkins, Dukan: (1) severely restricts fats and (2) includes 1.5 tablespoons of oat-bran fiber. Dr. Dukan also stresses the importance of drinking enough water (at least 1.5 liters/d).Phase 2: Ongoing Weight Loss (Cruise). Average length two to six months. Oat-bran fiber is increased to 2 tablespoons daily. Nonstarchy vegetables are added, alternating between a day of unrestricted (nonstarchy) vegetables, and a day of only protein (like during the attack phase), with zero carbs (no veggies).Phase 3: Pre-Maintenance (Consolidation). Length five days for every pound lost (a person who lost twenty pounds in the first two phases will do this phase for one hundred days). Oat-bran fiber remains at 2 tablespoons. The attack/pure-protein diet is reduced to only one day per week (Thursdays) instead of every other day. Two slices of whole wheat bread, one piece of fruit, and one portion of cheese are allowed each day. Two portions of starchy food (grains, legumes, or potatoes) are allowed per week. During the first half of the consolidation period (five days for every pound lost), one may have one unrestricted meal per week—eating any food one desires, without overeating. And during the second half, one may have two “celebratory” meals/week.Phase 4: Lifetime Maintenance (Stabilization). Length is continual. Oat-bran fiber is increased to 3 tablespoons. Six out of seven days are “unrestricted,” while keeping to the good habits you have acquired. One day per week of attack/pure-protein diet (Thursdays). Take the stairs (not the elevator). In all the phases, Dukan stresses the importance of daily exercise. During the first two phases keep the exercises light, such as walking, because the diet itself is very taxing. Afterward more intense exercise is appropriate.Pros:1. Fast! The Dukan Attack phase is the fastest way to lose fat while maintaining muscle! It is faster than Atkins because instead of burning ingested fats, the body is forced to burn body fat for energy.2. Fiber. One of my biggest complaints with Atkins is the lack of fiber. Dukan solves that by stressing the importance of including a couple tablespoons of oat-bran fiber.3. Balanced and Feasible. Unlike the Atkins maintenance phase that keeps carbs below 10 percent, with Dukan you are not so restrained for six days of the week. For many people this makes the difference between the impossible and the possible. The idea of permanently having one day per week of restricted carbs is genius (extreme restriction from fats on that day I think is unnecessary), because it reduces one’s glycogen reserves, insuring insulin sensitivity and keeping one from storing fat as long as those reserves don’t get filled up.Cons:1. For people who are capable of getting sufficient fiber in real food, that approach is preferred to supplementation because it allows consumption of the many micronutrients and bioactive compounds contained in high-fiber foods. Calories from vegetables slows down the short-term fat-loss, but their benefits pay off in the long run, as vitamins A and D (plus calcium) help reduce fat-cell numbers and improve leptin balance.2. Phase 2 is quite difficult to adhere to. Many people might need a milder/slower approach.3. Legumes are very healthy, and high in fiber, protein, vitamins, and minerals. To totally abstain from them in phase 2, and restrict in phase 3 to two portions per week, is too restrictive, in my opinion.4. As with all diets, Dukan fails to address the problem that fat-mass decrease leads to a decrease in leptin. Without a way to increase leptin and improve leptin sensitivity, fat loss is very limited for most people.Notes:A person who carefully follows the Dukan instructions in the first two phases can expect dramatic short-term results. Most people desire a fast solution to obesity, and as Dukan delivers on this better than any other diet, it is no wonder he sold 20 million copies, and his book quickly became the most popular diet book of all time.Dr. Dukan is of the opinion that most people want (and succeed better with) detailed diet instructions and a rigid plan, as opposed to being taught principles of physiology enabling each person to make adjustments for their personal circumstances. Maimonides and Metabolism equips you with the knowledge of your opponent (your body). With the deeper understanding of your physiology and how your hormones work, you will know how to adapt your diet to any situation.Dr. Dukan admits that many people who attempted his methods “manage to keep going for a while but then lose their way, and some of the weight they lost goes back on.”(pg. 268) He also recognizes that with many people “resistance sets in, weight loss slows down, and one day the body resists a little more than on other days and weight loss comes to a halt”(pg. 290) The Dukan solution: “I prescribe what I call a ‘blitz operation’…four days of the Attack diet’s pure proteins without any deviation, restricting salt, etc.…” (pg. 291) This solution reminds me of how we used to fix the TV when we were kids. We’d smack it. If that didn’t work, we’d smack it again. If necessary, we’d smack it harder. Heck, sometimes it worked!It’s safer to go with a more conservative approach. Even though the idea of FAST weight-loss is appealing, too often it sets up a fast rebound. Like charging into a slingshot, the faster one hits it, the faster one bounces in the opposite direction. That’s another reason to include high-fiber vegetables in the first phases every day. Once the body is accustomed to Dukan’s pure-protein attack, adding in necessary foods, such as vegetables, may be used by the body to halt fat loss.Criticisms:1. Lipid-phobia. Dr. Dukan writes: “Lipids (fats) are the absolute enemy of anyone trying to be slim…Since Atkins appeared, opening the way for lipids by demonizing carbohydrates…cholesterol and triglyceride levels rise dangerously, some people paying for this with their lives.” (pg. 18)Refer to the studies in Maimonides and Metabolism, and you will see that Dr. Dukan is wrong; cholesterol and triglyceride levels drop significantly on the Atkins very-low-carb diet, despite ingesting more lipids.See also the meta-analyses in Maimonides and Metabolism. Very-low-carb diets that are fueled primarily by proteins and lipids help lower insulin and glucose levels, a very important benefit for diabetics and prediabetics.Omega-3 is an essential fat required to include in the diet, and certain vitamins require dietary fats to be absorbed.Reducing dietary fats to a minimum helps speed fat loss, but there’s no reason to go overboard by creating a fear of one of the three macronutrients.2. Fat cell number blooper. Healthy adults have between 25 and 30 billion fat cells, which contain about twenty to twenty-five pounds of fat. When fat mass increases, the fat cells stretch like balloons to contain it. The average size (weight) of an adult fat cell is about 0.6 micrograms, but they can vary in size from 0.2 micrograms to 0.9 micrograms.When a person puts on fat, at first that stretches the fat cells without changing the number, but as time goes by, if the added fat mass remains, the body adapts by gradually adding more fat cells. That explains why a typical person who has been overweight for years can have 50 to 75 billion fat cells, to accommodate their twenty to sixty excess pounds of fat (beyond the twenty to twenty-five pounds of healthy fat mass).The way The Dukan Diet explains fat cell increase leads to a seriously mistaken perception: that a person can put on fat up to a 28 BMI without adding fat cells, and if they continue to put on more fat, somewhere between 28 and 29 BMI their 25 billion fat cells suddenly all simultaneously divide in two, yielding a total of 50 billion fat cells instantaneously! Dr. Dukan writes (pgs. 227-28):“It is important to pinpoint simply and concretely the moment in their weight history when there is this risk of cell division….” “If the weight gain continues, the adipocytes hypertrophy, or enlarge, and reach the limit of their elasticity. At this critical moment, any additional weight gain triggers a new and exceptional event, completely changing the future and prognosis for weight problems. No longer able to contain any more fat the adipocyte cell DIVIDES into two daughter adipocyte cells. This simple division suddenly doubles the body’s capacity to make and store fat….” “I was able to work out statistics that enabled me to pinpoint this moment as being after BMI 28 has been reached and going toward BMI 29.”3. Oversimplification of time needed to adapt to new lower body weight. Dr. Dukan writes (pg. 109): “The high-risk period for regaining weight lasts about five days for every pound lost, 30 days or a month for six to seven pounds, and 100 days for a loss of 18–20 pounds.”There are more factors that influence the length of the high-risk period, such as how long the person was overweight. If a person recently put on twenty pounds, the risk period of regaining it once they’ve gotten rid of it is short compared to a person who has been living for many years with the extra twenty pounds, as his or her body has accustomed itself to the higher weight with a corresponding number of fat cells. The person who has been overweight for years has a higher homeostatic weight level, which their body is naturally set to.Another influencing factor is the percentage of fat mass lost. For a 130-pound woman who dropped weight to 110, the loss of twenty pounds of fat (i.e., 50 percent of her total fat mass) will take much longer to acclimate to than a 600-pound obese man, whose twenty-pound loss constitutes less than a mere 5 percent of his total fat mass. This woman will have a dramatic reduction in circulating leptin, as her fat mass has been cut in half. This man won’t experience a significant reduction in leptin, because his fat mass only decreased by 5 percent.4. Desperate and dangerous…Dr. Dukan recommends taking cold showers, sucking on ice cubes, and eating one’s food cold (pages 229-33). These methods will burn calories, but there is a risk of becoming ill. Losing fat reduces leptin, which weakens the immune system. Combining extreme dieting with cold showers may push people beyond their limits.