THE METABOLISM OF FAT 569 



passes beyond a certain point it causes obvious changes in the contours 

 of the body, and often some embarrassment in its movements. This 

 condition is termed obesity. It is extremely difficult to say when the 

 condition oversteps the physiological boundary and becomes actually 

 pathological. Some individuals who are notoriously stout are noted 

 also for their intellectual activity, and may not fall below the average 

 even in the ordinary kinds of physical effort. It would be an exaggera- 

 tion to speak of such persons as suffering from a disease. In other cases 

 the pathological stamp is clearly imprinted upon the metabolic anomaly 

 which leads to the overfilling of the fat depots. This is perhaps best 

 illustrated in those cases of extreme obesity in children where, in spite 

 of the intense metabolism associated with growth, with the restless 

 muscular activity characteristic of that age, and with the relatively 

 great surface through which heat is lost, great quantities of fat continue 

 to be put on. Muscular activity by itself is no certain antidote to or 

 prophylactic against obesity, and it is a mistake to suppose that the 

 condition is exceedingly rare among manual workers sufficiently well 

 paid to be able to gratify their tastes in the quality and quantity of 

 their food. Statistics or rough estimates covering the whole of the 

 hand-workers of a country throw no light on such a question, for few 

 indeed are the lands where the masses of the people have such well-filled 

 purses that they are able to nourish themselves according to their wishes. 

 While it is true that the great majority of normal individuals (although 

 not all, since even in the fattening of stock for market some animals are 

 rejected as bad feeders) can be compelled to lay on fat when overfed 

 with fat and especially with carbo-hydrates, and prevented from taking 

 much exercise or from losing heat freely, the most important factor in 

 the excessive storing of fat by human beings leading a free life seems to 

 be an anomaly in the metabolism which permits the machine to be run on 

 less than the usual amount of fuel. From the point of view of thermo- 

 dynamics the fat man, in very many instances at least, grows fat and 

 fatter because his body is a machine whose ' efficiency ' is greater than 

 the normal that is to say, a machine which is capable of doing a given 

 amount of work and of keeping itself in repair with a food intake of 

 smaller heat value than is usually needed. Whether this anomaly is to 

 be considered a metabolic fault or a metabolic virtue depends largely 

 upon the ease with which the intake is adjusted to the actual require- 

 ment of the body. If the adjustment is rendered accurate, the man 

 with the anomalous tendency to put on fat, the adiposophil, ashe might 

 be called, is in all probability just as well off in every physiolog ical sense 

 on a smaller diet than a so-called normal individual of the same age, 

 weight, and daily routine, on a larger quantity of food, and on this 

 smaller diet he does not become fat. In this connection it may be 

 recalled that, in speaking of the blood-flow in the hands and feet (p. 127), 

 which are in this relation to be regarded as essentially an ' outcrop ' , 

 of the cutaneous circulation, it was pointed out that some healthy 

 persons have habitually small flows and a habitually cool skin which 

 perspires little, in comparison with others living practically the sam e life; 

 It was suggested that this difference in the blood-flow through the skin, 

 which of course would correspond with a difference in the rate of heat 

 loss, and therefore in the rate of heat production, may be correlated with 

 a difference in the intensity of the metabolism and the intake of food. 



The difficulty of adjusting the appetite to the actual physiological 

 requirement is perhaps the real anomaly in adiposophilia. Several 

 factors seem to be involved in the group of sensations comprised under 

 appetite and hunger (Chapter XVIII), and the onset and intensity of 

 these sensations are unquestionably influenced by habit. The real 



