Behaviors do not exist in a vacuum: Health behaviors are shaped through a complex interplay of determinants at different levels. For example, physical activity is influenced by self-efficacy at the individual level, social support from family and friends at the interpersonal level, and perceptions of crime and safety at the community level. Ecological models suggest that these multiple levels of influence interact across levels. For example, social support for exercise from co-workers may interact with the availability of exercise equipment at the worksite to lead to increased physical activity.

Traditionally, and especially in clinical settings, strategies to change health behaviors have focused on individual-level factors such as knowledge, beliefs, and skills. As ecological thinking has gained currency, intervention strategies have broadened to target factors at other levels of influence such as organizational policies and the built environment. This recognition of the complex range of factors that shape health behaviors can make the selection of intervention strategies daunting.