In the 1920s American physician George Draper proposed an ambitious new program to explain the causes of disease on the basis of body types--tall, short, fat, thin, muscular, or flabby. Draper tried to explain why, even in a group where every member has been exposed to the causes of disease (infectious or otherwise), some individuals get sick and others resist disease. Today we usually think some people have greater resistance to disease than others, and explain it through immunology. Draper explained the same resistance to disease through strong and weak body types.
Draper was a well known expert in Infantile Paralysis (polio) and was Franklin Delano Roosevelt's personal physician.
Draper G, Dupertuis CW, Caughey JL. Human Constitution in Clinical Medicine. PB Hoeber, Inc. New York, 1944