570 METABOLISM, NUTRITION AND DIETETICS 



question in many cases of obesity may be not why the metabolism is 

 managed so parsimoniously that is, in the physiological sense, so 

 thriftily but why the fat man or the man tending to become fat still 

 experiences so strong a desire for food after he has eaten what in pro- 

 portion to his metabolic wants is enough, whereas the man with no 

 tendency to obesity is no longer hungry after he has eaten an amount 

 of food sufficient for the requirements of his tissues. Is there here 

 perhaps an anomaly in the nervous mechanism in virtue of which, for 

 instance, the gastric hunger contractions are more readily initiated 

 and less easily stilled than in the normal person ? It is recognized 

 that in the usually much more serious anomaly of the carbo-hydrate 

 metabolism, diabetes mellitus, the nervous element may be important. 

 The influence of the loss of certain of the internal secretions on the 

 deposit of fat will be alluded to in the next chapter. 



In the treatment of obesity the factor of appetite and hunger control 

 has to be specially kept in mind. Bulky but comparatively innu- 

 tritious food, such as green vegetables, e.g., in the form of salads, should 

 form an important constituent of the dietary, since the mere distension 

 of the stomach staves off hunger. The total heat value of the food 

 must be reduced gradually. Carbo-hydrates must be largely excluded, 

 and also fats, although a certain amount of fat, say in the form of 

 butter, is permissible and even beneficial as aiding in the passage of 

 the food along the digestive tube. Alcoholic beverages are in general 

 contra-indicated, because alcohol, as an easily oxidizable substance, 

 protects the carbo-hydrates and fats from oxidation, and perhaps also 

 because the normal oxidative power of the tissues may be depressed by 

 its habitual use. On the other hand, tobacco smoking, which has some 

 power of inhibiting the gastric hunger contractions, may be permitted. 

 Muscular exercise, cold baths, light clothing both during the day and 

 at night, and a cool environment, are favourable to the reduction of 

 fat by increasing the consumption of material and the loss of heat, 

 just as a sedentary life in an overheated house in a person predisposed 

 to obesity, and eating too much for his requirements, favours the 

 putting on of fat. But if the appetite of the patient is allowed to 

 govern the intake of food, the increased decomposition brought about 

 by exercise, etc., is very likely to be balanced by an increased ingestion, 

 and no progress will be made. 



Metabolism of Sterins or Sterols. It has been previously stated 

 that cholesterin appears to be the only representative of the sterins 

 in the higher animals. Its source and function have been much 

 discussed of late years. As to its source, there seems to be no 

 reason to believe that any part of the cholesterin of the tissues is 

 formed from decomposition products of ordinary fats, carbo- 

 hydrates, or proteins. It is probably entirely derived from the 

 cholesterins of animal, and the phytosterins of vegetable food. On 

 this assumption, its metabolism, unlike that of the great groups of 

 food substances, is carried on in a closed circuit. Evidence that 

 it can be synthesized from other substances in the body is lacking. 

 No increase in the cholesterin has been observed during the develop- 

 ment of eggs, and the cholesterin content of growing chickens 

 appears to correspond to the sterins taken in the food (Gardner). 

 The portion of the cholesterin which is ingested in the form of esters 



