The human brain is a marvel.This is not a self-help book, although it might serve that purpose. It is a review of scientific data on the problem posed by overweight, but it is more than that, the book also gives a simple answer to a complex problem.I am an 80 years old man and I weigh 74 Kg. My Body Mass Index is 23.35. Overweight has been a keen interest in my life of the last thirty years or so. In 1988 I had recently quit my academic life, legally opting for retirement after 27 years of work. My weight had increased due to my new activity: I was now a partner and administrator of a fine restaurant in Caracas. Being a doctor (UCV, 1961) and Biochemist (M.Sc. UCL 1965, Ph.D. UCH 1974) I decided to do something on the subject: I started reading academic articles on the subject.I can only say that after years of being a lab research worker, with all the social conduct that life means: reading journals, lab experiments searching for 'the secret of life', talking shop with colleagues while sipping a drink, meetings, etc. I found that research on body mass regulation, something that attains so intimately with what is human and its disconcerting variety is something utterly different to working with rodents or cultured cells. I felt very odd immersed in literature about overweight and obesity. And that was in spite of having worked a few years back helping a colleague, an endocrinologist not used to lab-bench work, to do research on the action of insulin (It had to be done using rat adipose tissue). [Pimentel, E., González, C.A., González-Mujica, F., (1974) Effects of insulin and glucose on subcellular fractions of rat adipose tissue. Acta Diab. Latina. 11, 206-212]. By the way, a curious event, that colleague, Enrique Pimentel, later became Director of the Instituto de Medicina Experimental, Universidad Central de Venezuela, a position that would be my own towards the end of my academic life. (1985-87).Anyway, what matters is that studying the subject of weight control I became an enthusiast and got into it with persistence, even as my life was in a totally different environment. I even counseled clients of the restaurant! Perseverance paid off, about three or four years ago I found a lead into a theoretical solid base for the answer of a puzzle always present in the minds of scientists, doctors, nutritionists, dietitians and fat people: Why so many differences among people trying to lose weight? Why the 'rebound' effect? Why so much imposture trying to look like science? What I had found was that it is fasting that makes things so interesting. Not that the problem is solved. No. But fasting has the potential for a coherent theoretical explanation of the problem. There is no doubt that modern man is eating in a manner that does not fit with our genetic endowment. With this core belief, research begins to make sense. Yet, I hold that with what we know today, it is possible to help those who are shortening their lives and turning their backs to a happier life due to erroneous nourishment. A final word, possibly the most important, may be the ONLY important one of this little new book. I have the hunch that I have seized Ariadna's ball of wool and with it someone may enter the maze of insulin resistance with the thread between their fingers. Without false modesty, I believe that postulating that insulin resistance is actually a defense mechanism of the human body against the pressure of excess calories, might prove to be a firm base to look at the problem from a different point of view and lead to researchers designing experiments that find answers to the problem millions of people are suffering. If this should happen, I will be very proud of having spent hours reading papers on the subject. If I am wrong, it is fortunate that the damage caused by my daring will be very small, if any. Pity, this will not be the case for my ego.