The following figures give an idea of the frequency of the coinci dence of diabetes and obesity : Frerichs had 59 cases of obesity among 400 diabetic patients, or 15 per cent., Seegen 30 per cent., and Bouchard 45 per cent. It has been remarked by some (Bou chard, Kisch) that in families in which obesity is common, one or another member who is himself not obese suffers from diabetes. Of Bouchard's patients 36 per cent. gave a history of obesity among their ancestors.
In the treatises on diabetes in the text-books the view is gener ally held that diabetes occurs secondarily to obesity, and this form of the disease is therefore designated as " lipogenous diabetes." Kisch in particular holds to this view. Others express themselves with great reserve concerning the exact relation existing between the two affections, although admitting the fact of such relation. Seegen be lieves that obesity is frequently a precursor of diabetes. I myself have already expressed the opinion, in my work on " The Pathology of Metabolism," that our present knowledge of the mutual relations of carbohydrate and fat exchange permits of a more profound under standing of the interdependence of diabetes and obesity than is ordi narily admitted. I have already laid stress upon the belief that, in every case of true diabetes, not only the exudation of carbohy drates but also their conversion into fat must be restricted. Were the first-named function alone interfered with there could be no long continued and excessive glycosuria, especially if the diet were one poor in carbohydrates, so that the entire amount of sugar thrown into the circulation would be comparatively small and very much below that ordinarily taken up from the intestinal canal of a healthy man living upon an unrestricted mixed diet. In such a case the carbohydrates not consumed in the muscles, glands, etc., would be seized upon by the fat-forming cells and, through welding together of the molecules, be compressed into fat, just as occurs in the healthy organism. Hyperglycaemia and glycosuria can follow only when the fat-forming as well as the oxidizing cells have lost their power of arresting the sugar molecule. It is possible that both the consumption (oxidation) and the storage (fat conversion) of the material are interfered with by a common cause, as for example the resistance of the diabetic tis sues to glycogen formation, but on this point we have as yet no cer tain knowledge.
The following consideration seems to me to be justified by what has just gone before. It may be conceived that there are cases iu which at first the power to burn- up sugar in the organism is alone interfered with, while the conversion of carbohydrates into fat still goes on. Under these circumstances the working cells of the body are richly bathed in a nutritive sugar solution; nevertheless they are starved because they cannot, or at least can only with difficulty, seize upon the sugar molecule. As a consequence of this there occurs a sort of tissue hunger which excites reflexly a sharper appetite and leads to the ingestion of a greater quantity of food. The latter re sults directly in an increased deposit of fat. Such individuals are diabetic, only they do not excrete sugar externally through the urine but rather into the freely accessible layer of adipose tissue. The adiposis masks the diabetes ; we have to do, in fact, with a " diabeto genous obesity," as I call the condition in opposition to the common teaching of a " lipogenous diabetes." A logical analysis leads us to the following schema: a. There are cases in which the consumption of sugar and its con version into fat are simultaneously restricted—glycosuria of varying degrees of gravity and emaciation (ordinary diabetes).
b. There are cases in which only the burning up of sugar, and not its conversion into fat, is interfered with,—obesity without glyco suria (masked diabetes) ; these pass readily at a later period into a. Cases in which the consumption of sugar is restricted and the heaping up of carbohydrates in the fatty tissues is also more or less interfered with—obesity with consecutive glycosuria (ordinary dia betes of the adipose).
I regard this theory as by no means filling all the gaps existing in the present state of our knowledge, but I think that the teaching as far as it goes is warranted. The fact of a relationship between dia betes and obesity is, in the light of my theory, no longer question able, but follows logically from the connection which has been found in recent years to exist between carbohydrate metabolism and fat for mation. It may, indeed, be said that, even if practice had not long since spoken correctly, theory would have forced us to construct an hypothetical relationship between diabetes and obesity.