Study participants had physical examinations that included weight, height, and waist measurements, and they supplied blood samples. Using the blood samples, the researchers determined each man's genetic makeup for three genes of the renin–angiotensin system: the ACE gene, the AGT gene, and the angiotensin II type I receptor (AT2R1) gene. They then looked for associations between the forms of these three genes and being overweight (defined by a measure that considers weight and height) or having abdominal obesity (defined by waist measurement). Of the 959 men, 314 had information from 1975 through 1995, enabling the researchers to examine the development of obesity over 20 years in relationship to the renin–angiotensin genes.