While genetic factors play a role in the development of obesity, the dramatic increase of its prevalence in the past years strongly suggests that environmental factors are largely responsible. The wealth and variety of food supply available 24h/day and throughout the year, the change in dietary habits due to time constraints and the change in physical activity due to technological advances all create a 'toxic' environment responsible for obesity and eating habit disorders. This manuscript describes and discusses the results of a systematic review of environmental opportunities & obstacles for physical activity and dietary intake influencing the obesity epidemic among children and adolescents. Although evidence clearly shows the impact of the environment on obesity related lifestyle factors, evidence for effective strategies combating this obesogenic environment is very scarce. Interventions aiming to change environmental factors in order to reduce obesity may include taxes/subsidies encouraging healthy eating or physical activity, extra provision of sporting facilities, efforts to improve safety and accessibility of walking, cycling or play areas or attempting to influence social meanings/values attached to weight, food or physical activity. It is clear that some level of institutionalization of systems that support the desired changes is required to sustain environmental and social changes in the long-term. At last, it is important to note that better-designed and -conducted research on the true importance of the interaction between environmental factors and psychosocial factors, including the micro- and the macro-level, for obesogenic behavioral change is needed to reassure the success of large-scale environmental change interventions.