Résumé : Obesity is defined as an excess body fat leading to impaired health. It is measured by the Body Mass Index (BMI), computed from weight and height of an individual. A BMI greater or equal to 30 kg/m
2 defines obesity. Increase in BMI is associated to overall and cardiovascular mortality, as well as respiratory and osteo-articular conditions. Obesity prevalence was estimated in France in 2006 at 16.1% [95% confidence interval] [14.8-18.9] in men and at 17.6% [15.0-20.2] in women. Prevalence is increasing in France, as well as in other western countries. Developing countries face a very high increase in obesity prevalence. Rapid transformation of agricultural production and profusion of food supplies as well as increase in sedentary behavior in the population participate in the increase of obesity prevalence.