The INSEE national surveys in 1980 and 1991, and the OBEPI study in 1997, allowed to study the prevalence of overweight and obesity in France, as well as its increase during these past years. The number of adult obese individuals remained stable between 1980 and 1991. The 1997 estimation suggests a moderate increase. By contrast, the number of obese children has increased between 1980 and 1991, whatever the level of study of the mother. Several diseases are strongly linked with obesity, such as hype ruricemia, hypertension, coronary heart disease, diabetes mellitus. Thus the declared prevalence of diabetes is 2 % when BMI ranges from 18.5 to 25 kg/m(2), and reaches 20 % at a BMI > 34 kg/m(2) with age ranging 40-70 years old. The presence of obesity during childhood is also correlated with an increased mortality, with an enhanced prevalence of coronary heart disease, hyperuricemia, colon cancer in men, and joint disease in women during adulthood. An increase in the prevalence of diabetes is expected in the near future: demography, as children born after the war will reach age of 55-75, the lowering of glycemic threshold for the diagnosis of diabetes, increased prevalence of obesity a re the ma in explanations. Our health care system will need to evolve in order to deal with this increased number of patients, and measures have been recently set for that purpose.