ENERGY VALUE 467 



relatively rich in lipase, hence is to that extent peculiarly fitted for storing 

 and distributing fats. 



Whether or not there are other special tissues involved in this imme- 

 diate problem is not adequately studied. It is quite possible that many 

 of the adipose tissues are involved. Certain tissues of the body are great 

 fat storage tissues subcutaneous, intermuscular, peritoneal, etc. These 

 tissues readily yield their fat in time of starvation but it is not known that 

 they are concerned in the production of lipase at this time. 



Destination of Fats, Obesity, Diet, etc. It has already been empha- 

 sized that fats are a direct source of energy of oxidation. This is their 

 primary function in the body. If fats are taken in excess in the food, or 

 are produced in excess from carbohydrates of the food, then they accumu- 

 late in great quantity, especially in middle and old age. This accumu- 

 lation gives rise to the condition of obesity which is a condition of excessive 

 fat storage. In many of these cases there is persistent storing of fat in the 

 presence of a dief of low energy value and when considerable physical 

 labor is expended. It seems that such persons have a perverted or at 

 least disturbed fat metabolism. The explanation is very often found in 

 deviation of function of some endocrine gland. For example, in decreased 

 secretion of the posterior lobe of the pituitary there is an increase in 

 sugar tolerance associated with a tendency to accumulate large quantities 

 of fat. Defects of this character are met by attempts to supply the 

 deficient internal secretion. 



Obesity may result purely from over eating, in which case the person 

 must use self restraint to restrict the quantity of food and the amount of 

 fat and of carbohydrates from which fats are easily produced. 



In many persons and under certain conditions, the oxidation of the fats 

 is incomplete. This is indicated by an increase in the intermediary pro- 

 ducts, acetone, etc. This phenomenon gives rise to the condition of mal- 

 nutrition expressed by the term acidosis which belongs to the field of path- 

 ology to which the reader is referred. 



THE METABOLISM OF CARBOHYDRATES. 



Energy Value. The nutritive function of carbohydrates in the body 

 is to serve as a source of energy. They are oxidized, with the ultimate pro- 

 duction of carbon dioxide and water, and must liberate the same amount 

 of energy as when burned outside the body, i.e., 4.1 Calories per gram. 

 A given weight of dextrose, therefore, furnishes a little less than half the 

 energy of a corresponding weight of fat. 



Carbohydrates are strictly energy-formers and may be regarded as the 

 chief immediate source of the energy of oxidations, although they may be 

 synthesized into fats and possibly even contribute to protein formation. 



