Epidemiology of obesity

Obesity is a serious threat to public health worldwide [1-3]. In developed countries, obesity prevalence historically has been greatest among those of lower socioeconomic status, whereas in developing populations obesity was a condition of affluence. However, the prevalence of obesity (body mass index [BMI] ≤30 kg/m2) has risen steadily during recent decades among all the major population subgroups (e.g., gender, age, social class), leading obesity to replace more traditional public health concerns such as infectious diseases and malnutrition as a principal cause of illness [2]. Approximately 250 million individuals are clinically obese and it is estimated that by 2025 this number will increase to more than 300 million [2]. Among U.S. adults who at age 40 are non-obese, the estimated residual lifetime risk of becoming obese is close to 50% in both women and men [4].