In Norwegian adult men, body mass index (BMI) increased from around 25 kg/m(2) in the late 1960s to around 26.5 kg/m(2) in the late 1990s, and the prevalence of obesity increased from about 5% to 15% in the same period. In women the prevalence of obesity actually decreased from around 13% in the late 1960s to 7% in the late 1980s. However, during the last years the prevalence has also increased reaching about 13% in the late 1990s. It is important to note that both mean and median BMI has increased with a shift in the distribution to the right. The proportion of normal weight individuals has thus decreased, whereas the proportion of obese has increased. The increase in BMI has occurred in different age groups. Although obesity is associated with low education and a sedentary lifestyle, the increase in BMI has also occurred in the more educated and physical active.