We examine the effect of lifestyle on the prevalence of overweight and obesity among adolescents. A cross- sectional study was carried out in 7 secondary schools in the state of Mostaganem, including girls and boys whose ages range between 15 and 19. The total sample included was 98 adolescents 34 boys and 64 girls their average age ≈18 years. It is shown that family forecasts related to the financial condition are in first- line risks obesity relative to genetic factors and level of prevention fatness stroke; eating degree energy calorie and eating behaviours are the most factors contributing to the prevalence of obesity and lack of regular physical activity is a key factor in weight gain and the prevalence of obesity.