Using systems science to understand the determinants of inequities in healthy eating

Abstract

Introduction: Systems thinking has emerged in recent years as a promising approach to understanding and acting on the prevention and amelioration of non-communicable disease. However, the evidence on inequities in non-communicable diseases and their risks factors, particularly diet, has not been examined from a systems perspective. We report on an approach to developing a system oriented policy actor perspective on the multiple causes of inequities in healthy eating.

Methods: Collaborative conceptual modelling workshops were held in 2015 with an expert group of representatives from government, non-government health organisations and academia in Australia. The expert group built a systems model using a system dynamics theoretical perspective. The model developed from individual mind maps to pair blended maps, before being finalised as a causal loop diagram.

Results: The work of the expert stakeholders generated a comprehensive causal loop diagram of the determinants of inequity in healthy eating (the HE2 Diagram). This complex dynamic system has seven sub-systems: (1) food supply and environment; (2) transport; (3) housing and the built environment; (4) employment; (5) social protection; (6) health literacy; and (7) food preferences.

Discussion: The HE2 causal loop diagram illustrates the complexity of determinants of inequities in healthy eating. This approach, both the process of construction and the final visualisation, can provide the basis for planning the prevention and amelioration of inequities in healthy eating that engages with multiple levels of causes and existing policies and programs.

Fig 1. An example of a policy actor mind map of the determinants of inequities in healthy eating.

Fig 2. HE² causal loop diagram of the determinants of inequities in healthy eating.

The HE² diagram is structured according to accepted principles of system dynamics [48]. The arrows indicate the direction and polarity of influence. The solid lines indicate positive polarity and the dashed lines indicate negative polarity. Positive polarity means that the initiating variable influences the receiving variable in the same direction of change (e.g. as the ‘distance between households and food retailers’ goes up, so does the ‘time spent travelling to food retailers’). Negative polarity means that the initiating variable influences the receiving variable in the opposite direction (e.g. when the ‘level of misinformation about unhealthy foods’ falls, an individual’s ‘ability to sort through conflicting health related messages’ rises). Polarities do not indicate the rate of influence, and it is important to note that change may occur at uneven rates within the diagram.

Fig 3. Core mechanism of the HE² diagram.

Fig 4. CLD for determinants of inequities in healthy eating, showing sub-systems.

The arrows indicate the direction and polarity of influence. Solid lines indicate positive polarity and dashed lines indicate negative polarity. Positive polarity means that the initiating variable influences the receiving variable in the same direction of change (e.g. as the ‘distance between households and food retailers’ goes up, so does the ‘time spent travelling to food retailers’). Negative polarity means that the initiating variable influences the receiving variable in the opposite direction (e.g. when the ‘level of misinformation about unhealthy foods’ falls, an individual’s ‘ability to sort through conflicting health related messages’ rises). Polarities do not indicate the rate of influence, and it is important to note that change may occur at uneven rates within the diagram.

Fig 5. Feedback between sub-systems and the social distribution of healthy eating.