NO SCIENTIFIC investigation is needed to detect the familial nature of obesity, but the extent of the contribution of constitutional, cultural and other environmental components is not at all clear. That it is especially important, however, to understand these etiologic factors is suggested by the failures experienced by those who have undertaken to treat long standing obesity. A firm grasp of the nature of the causes of the condition is the key to prevention, and the time to prevent is childhood.
Before going on to a discussion of heredity in obesity it might be well to state what is possible in genetic studies on human populations. Genetics is the study of heritable variation, and it attempts to describe the degree to which familial like-nesses and dissimilarities result from the action of genes in particular environments. In general, we suppose that gene action is biochemical, and that it is expressed in the control of metabolic reactions in the cells, whether by conferring specificity upon enzymes or by other means.
Several methods for such investigation are available. First we may study discontinuous variation in which differences between individuals are clearly measureable, and a population may be divided into two or several types without misclassification. Such differences are often found to be associated with differences in molecular specificity or quantitative differences in enzyme activity. If these differences are genetic in origin, they are usually found to be due to one or at most a small number of genes, and the intrafamily distribution of the characteristics will follow some mendelian pattern.
A second method involves the analysis of continuous variation. By this is meant differences between individuals which are so small as to make actual measurement of such differences impossible, and covering a wide range or spectrum, so as to form a continuum.
- Copyright © 1957 by the American Academy of Pediatrics