OBES'ITY, Coneut.ENm or INILYSAKCIA ( Lat. obrsitas, from obrsus, fat, p.p. of °bracer. to eat up. from oh, before. near rdrrc, to eat ). An abnormal deposit of fat under the skin and around the viscera. The amount of fat pos sessed by an individual may vary widely within the limits of health, hut so long as it does not interfere wills the bodily funetions or move ments. it is not indeed, a certain quantity is usefnl and necessary to protect the Va Hums organs and to maintain their leintierature. as well as to serve as a reserve supply of nutri tion. ( See Fars.) The normal proportion of fat to the whole body weight is given as about lift Pell lb to one-twentieth. Obesity may occur at any period of life. but llie lendeney to corpulence is greatest after forty. In women the predisposi tion is greatest after the first years of child-bear ing, and again after the menopause. In the prn duetion of obesity three great causes are active as a rule. These are heredity, overindulgence in food and drink, and lack of exercise. \Io•t persons over forty eat too much and exereise too little. Alcohol tends to fatten by substituting itself for food in the oxidizing process. Fat when once deposited favors tin deposition of more fat, for by acting as a non-conducting envelope to the body it prevents the radiation of heat, and so decreases the combustion of those substances which, when not used to produce heat, are stored up as fat. The immediate cause of obesity is generally a faulty assimilation due to some digestive derangement by which oxidation of the albuminous elements of the food is interfered with. The carbohydrates are not as was long thought directly to blame, since they are readily converted into carbon dioxide and water. On account, however, of the ease with which the carbohydrates are oxidized, the albuminous ele ments of the food undergo incomplete oxidation, are not so fully decomposed, and the fat is in reality derived from them. The fatty portions of the food are not so prone to cause undue deposition of fat as are the carbohydrates, since they interfere less with the conversion of the nitrogenous elements, and are less easily oxi dized.
The symptoms which may attend extreme de grees of corpulence are a falling off of mental and physical activity, shortness of breath on the least exertion, and impairment of the functions of respiration, circulation, and digestion, together with aniemia and muscular weakness. This, however, is an extreme picture. It is a matter of daily observation that obesity is compatible with a high degree of mental and physical alert ness and general good health.
Many plans of treatment, based on systems of exercise and diet, have been advocated for the reduction of fat, the most notable being those of Banting, Ebstein, and Oertel. All of these systems have for their object the regulation of exercise in such a way that oxidation may pro ceed in a normal manner, and regulation of the diet so that a less quantity than normal of the fat-producing elements is taken in. This object
is attained in various ways. in the method of Banting the total quantity of food is retwed, the liquids restricted, and the fats and carbohy drates excluded. Ebstein's method permits the use of fats, but eliminates the carbohydrates. Oertel's system is especially intended for in dividuals with cardiac complications, and con sists of three parts. First, the redaction of liquids with promotion, by baths or other men Ilq Of perspiration; second, restriction of the diet largely to protcid substanees: and third, the taking of graduated exercises in walking up hill. Cathell proposed some years ago a method which was entirely independent of diet and exercise. This was the taking, on alternate days. of Kis singen and Vichy mineral waters. with the addi tion, in obstinate eases, of lemon juice to the Kissingen, and aromatic ammonia to the Vichy. Thyroid extract enjoyed for a time a reputation as a fat-reducer. but its tendency to interference with the heart, which is apt to be weak in obese persons, makes it a somewhat dangerous drug. Among other substances which have been used for this purpose are iodine, bromine, mercury, lead, arsenic, lemon juice, sour wines, vinegar, Phytolaeca, Gulf weed. and bladder wrack. Many of these, while having an influence on the fat,,, act as slow poisons and damage the assimilative organs. so that their ultimate effect is injurious.
OBI, 614), or OB. The westernmost of the great rivers of Siberia (Map: Asia, tt 2). It rises in the Altai Mountains, and tlows north west, then north through the Siberian govern ments of Tomsk and Tobolsk, emptying into the Arctic feenn through an immense estuary. the Gulf of Obi, which is 600 miles long and an miles in average width. The length of the ricer itself above the estuary is about 2500 miles, and it is nearly two miles wide at its mouth. After emerging from the foot-hills of the Altai range the river flows fur the remainder of its course through an almost perfectly level country con sisting first of sandy steppes, then of rich tracts of fertile soil, and finally of vast marshes. In its lower course it divides repeatedly into paral lel arms connected by vrosx•chane1s. forming a network of islands, which during floods are submerged under sheets of water many miles wide. Although not yet extensively used as a waterway, the Obi with its tributaries presents, a total navigable length of over 9000 miles. In summer the main river and all its larger tribu taries are navigable almost to their sources, and during the spring floods many secondary tributaries can be ascended by light-draught steamers. The river is ice-bound near its mouth from October to June. Of its numerous tribu taries the largest is the Irtysh (q.v.), which is considerably longer than the main stream from the point of confluence.