This study describes aspects of obesity research, and especially the thinkingon theetiology, thedifferentiationofindividualformsofobesity,the problem of the size of fat cells, the assessment of obesity as a cardiovascular risk factor and the problem of the fatty infiltration of the liver in obesity. A summary of the literature on the subject is given. I n t r o d u c t i o n a n d D e f i n i t i o n Numerous definitions of obesity exist; let us take just one as representative: "Obesity is the propensity of the organism to excessive weight increase which occurs under certain conditions. It can lead to a clinical picture which includes a disturbance of the ratio of the body weight constituents in the sense of a more or less pronounced increase in the proportion of fat. Associated with this there may be physical and mental dsturbance of the organism"'.The cause of the obesity is always a disturbed energy balance, in that the intake of energy by the ingestion of food is greater than the energy consumption.The extent of the obesity is generally stated as a percentage overweight in relation to the normal weight of the person concerned. There are a number of systems of calculation and measurement relating to the boundaries of the normal weight range and hence also to the nosologically exact definition of the concept of obesity as a disease;as a rule, however, the normal body weight is calculated roughly in accordance with Broca's rule (body length in cm -100 = ideal weight in kg). If the normal weight according to Broca is exceeded by 20%, then obesity is present. However, the weight determined by using Broca's formula is related solely to the length of the body, and the peculiarities of the physique of the person concerned are not taken into account.In many cases the definition and quantification of obesity is also made on the basis of the ideal weight, with the ideal weight being designated as that at which, given a certain body length, the maximum life expectancy is anticipated in purely statistical terms'. As with the Brocu index,in theideal weight, which is m a d y based on an association between life expectancy and the ratio of body weight to body length, no account is taken of differences in the composition of the body" and constitution of the body4,". Doubts have also been expressed as to whether the data which are used as the basis for the calculations, and which were determined many years ago, are representative of the present population of the USA, and also especially of groups of the West European pop~lation"~~. On account of its ease of use the Broca index has held its own in clinical practice in spite of many disadvantages. Finally let us also mention that the terms adiposity, obesity, overweight and corpulency are used as synonymous designations for the disease. N u m b e r a n d s i z e of f a t c e l l s The questions of particular importance with regard to the etiology of obesity and also to the understanding of the results of therapy, are the number of fat cells deposited in theStandpunkte in der Erf...
