Résumé

Is Obesity a disease or only an adaptation?

Mme Martine LAVILLEa

a Centre Hospitalier Lyon Sud, Hospices Civils de Lyon

Obesity is increasing all around the world at an epidemic rate. Although France is not the most affected country, the last OBEPI study shows that 14.5 % of the population was obese and 31.9% overweight. In fact, only 50% of the population has a normal body weight (18

Increasing body weight is an adaptation to the large changes in life-style that are occurring with a decrease in physical activity and the development of sedentary behaviours as well as changes in food habits patterns. This leads to a positive energy balance and the body has no other solution than to increase fat mass. The increase in obesity prevalence is problematic, as this condition is associated with health complications such as diabetes and cardiovascular diseases, more particularly when the excess body fat is stored in the deep abdominal region. Cut-off values for obesity, de?ned as a body mass index (BMI, kg=m2)>30 come from the epidemiological observations of the large increase in mortality risk above this level. However, we can found some people with large obesity and lacking of metabolic alteration usually associated to obesity (obese metabolically normal), subjects only prone to mechanical complications of obesity. On the other hand, patients with total lack of fat, as seen in lipoatrophic diabetes, have also important metabolic complications. Understanding the underlying mechanisms leading to ectopic fat accumulation are of major importance to detect subjects for whom weight gain will be particularly deleterious. However on a Public Health perspective, labelling obesity as a disease is a necessary step in a campaign to combat obesity. Prevention by deep changes in lifestyle is mandatory as many of chronic diseases such as diabetes, cardio-vascular diseases, cancer could be prevented by better management of body weight.