In all cases of progressive obesity the intake of food is greater than the output of energy, and the problem to be solved is to arrange a proper proportion between the two. As soon as this is accomplished the accumulation of fat is arrested. During the reduction proper, however, the intake of food is to be rendered smaller than the output of energy. Under such conditions the deficit is borne by the tissues of the body proper. According to the principles that have been formulated in a previous lecture, the body has a tendency to cover this deficit from its adipose tissues, while at the same time manifesting a tendency to spare its albumen content. In obese individuals, who possess an enormous amount of reserve material in their fat layers, the body albumen is protected much better than in subjects who are in a medium or in a poor state of nutrition. Nevertheless, body albumen may be sacrificed if one does not proceed properly. This was shown by the nitrogen balance studied by F. Hirschfeld, in 1893. His patients in the course of a reduction cure lost from 1 to 3 g. of nitrogen daily (corresponding to about 6 to 8 g. of albumen). Exactly at the same time C. Dapper and I, jointly, published a series of investigations that demonstrated that the loss of nitrogen can be fully obviated and that it is possible to dismiss the patients at the end of a reduction cure with the same amount of body albumen as they possessed when they came. This question has frequently been studied since that time, and I have always kept this point in view. The most important summary of my conclusions is that relatively high amounts of albumen, administered together with relatively high amounts of carbohydrate, are the proper means to protect obese subjects undergoing a reduction cure from loss of nitrogenous body substance. The introduction of fat may and must be correspondingly decreased. I will have occasion to speak of this in more detail later on.

The rules in regard to feeding that obtain in reduction cures must all be formulated upon the science of caloric feeding. This does not imply, of course, that in each case and on each day a tedious calorimetric study of the diet should be carried out by the physician or the patient. Only in really energetic reduction cures (reduction cures of the third degree, see below) do exact caloric determinations become necessary. This does not constitute an impossible task nor one that cannot fairly be demanded, because strict reduction cures after all belong to the domain of sanatorium treatment or should be carried out only by physicians who occupy themselves especi ally with problems of this character. A physician who is not fully familiar with caloric calculations of the food should never undertake the management of an energetic reduction cure.

It is, of course, impossible in this place to give detailed rules, and I will limit myself to the elucidation of general principles. In every case a general estimate should precede the actual reduction cure in order to determine the true demand of the patient for food (amount of the "maintenance diet"). From the product obtained by the multiplication of the body weight by the caloric demand pro kilo (see Vol. VIII), a certain sum must be deducted in obese subjects, because adipose tissue does not participate in the transformation of energy, this function being relegated exclusively to the protoplasmic substance. One must, therefore, calculate by about how much the body weight of an obese patient exceeds the weight of a normal individual of the same height. This difference must be included in the calculation. We will assume, for instance, that an obese patient weighs 100 kg.

The normal weight of an individual of the same height we will say is 70 kg.

The occupation and the amount of labor performed by the patient we will assume to be such that under normal conditions 37 calories pro kilo of energy would be consumed (see Vol. VIII).

In order to calculate the maintenance diet of such a patient the figure 37 must be multiplied not with his actual weight, that is, 100 kg., but with his normal (ideal) weight, that is, 70 kg. And we arrive thus at the product of 2500 calories as his "maintenance diet." In this method of calculation there are, of course, included certain sources of error, but they are not of great importance. Practically I have found that this method works out very well. If this figure is assumed as the basis, then we must estimate as closely as possible, the nutritive value of the diet that the patient actually is in the habit of ingesting, and we will almost invariably find that this sum is greater than the calculated "maintenance diet." It now becomes a relatively easy matter to determine where one must begin to reduce the diet in order to bring down the total caloric value of the diet that this patient was accustomed to eat; besides, one must determine, in each particular case, whether it is advisable to proceed slowly or fast.