I will limit myself to a very brief discussion of the factors that lead to obesity. It is necessary, however, to indicate the main rules that should govern the treatment of obesity, for a careful understanding of the underlying principles is necessary before a reduction cure can be intelligently undertaken.

Under normal conditions there is an automatic regulation of the output of energy and the intake of food. A human being after having attained an optimum, that is, a medium average state of nutrition, adjusts himself to a definite amount of food that constitutes for each individual the so-called "maintenance diet"; the latter deviates upward and downward [according to the varying demands created by a varying amount of physical labor performed] from the average medium food intake. Of course, the exact amount of energy that corresponds to the consumption of energy on each day is not introduced during each 24 hours' period; but these differences become so completely equalized by small increases and decreases that many persons for years and for decades maintain their weight, that is, the resultant between intake and output, unchanged.

This finely adjusted normal regulatory mechanism is occasionally disturbed, sometimes forcibly, but more frequently by the cumulation of numerous small causes producing a large effect.