A systems approach requires seeing the whole picture and not just a fragment, understanding the broader context, appreciating interactions among levels, and taking an interdisciplinary approach (Leischow and Milstein, 2006). A systems approach highlights the importance of the circumstances, or context, in which an action is taken in order to understand its implementation and potential impact. Thus while investigators must, for practical reasons, establish boundaries to define the system being studied, they must also recognize that each system exists within and interacts with a hierarchy of nested systems (Midgley, 2000). In addition, appreciating leverage points or points of power within a system can help explain how a small shift in one element of a complex system can produce larger changes in other elements (Meadows, 1999). These advantages of systems investigation are particularly important for interventions targeting obesity, given their far-reaching impact on the population; solutions should be designed to maximize benefit and minimize negative consequences.
The systems approach offers a further advantage with respect to the well-recognized gap between research and practice, which limits the extent to which advances in research translate to advances in improving public health. Most efforts to