In the meantime I had gone to the medical school library, where I spent time learning more about the nutritional properties of meat and other proteins.
When my patient returned 5 days later, still in tip-top shape and having shed another 4 pounds, I told him to add fish and seafood, which he accepted with good grace because he had explored all that meat had to offer.
When at the end of 20 days the scales registered a loss of 22 pounds, I ordered another blood test, which turned out to be just as reassuring as the first one. Playing my ace, I had him add the remaining categories of protein: dairy products, poultry, and eggs. However, to allay my concerns, I asked him to increase his water intake to 3 quarts--twelve 8-ounce glasses a day.
He agreed to add vegetables, as I was beginning to worry that they had been absent from his diet for so long. When he came back 5 days later, he had not lost an ounce. He used this as an argument to go back to his all-protein diet. I let him have his way on the condition that he alternates this regimen with 5-day periods that would include vegetables, arguing that otherwise he risked vitamin deficiency. He did not buy that argument, but he agreed because he was suffering from constipation due to the lack of fiber in his diet.
This is how the first phases of the Dukan Diet were born, as well as my interest in obesity and weight loss. My patient had changed the course of my studies and my professional life. I worked to improve the diet, creating an eating plan that seems to me today to be both the most appropriate for the particular psychological make-up of overweight people and also the most efficient for weight loss based on real food.
However, over the years, I have come to the bitter realization that even effective weight loss diets are not effective in the long term. At best, the dieter slowly and imperceptibly drifts off course; at worst the weight piles back on again, usually because of stress, setbacks, or other problems.
It was seeing how the vast majority of dieters inevitably lose this war against weight that led me to design a plan that protects the accomplishment of reaching the target weight. The job of this Consolidation phase is to reintroduce, in increments, the basic elements of proper eating and to control a body that, stripped of its reserves, would be bent on revenge. To allow enough time for this rebellious phase and to make the transition acceptable, I fixed a precise time limit for the second part of my plan, easy to calculate and in proportion to the weight lost: 5 days for every 1 pound lost.
However, once the Consolidation phase was over, I saw my patients' old habits gradually creep back, thanks to the pressures of metabolism and the inevitable resurgence of the need to compensate for life's miseries with those thick, creamy, sweet comfort foods that craftily overwhelm our defenses.
I therefore had to resort to a measure that is hard to even suggest to people, a rule that I dare to call "permanent," the kind of shackle that all overweight people the obese or the just plain overweight-detest be-cause it is there for good. However, this rule, which needs to be followed for the rest of one's life but which guarantees real weight stabilization, applies to only a single day a week; a day that is predetermined, whose structure cannot be changed or negotiated but which bears amazing results.