Since obesity is an emergent property of complex adaptive systems, it behoves us to apply systems thinking and systems methods to understanding the problem and trying to reduce its prevalence. Systems science is based on cause-and-effect relationships, the whole as well as the parts, and changes over time.
System Dynamics models show us the nature of the biological challenges with obesity because the goal of the human energy balance system is to ensure that we eat enough food to approximately meet the current energy and protein needs of, and prevent the ‘perceived’ threats to, the lean tissue mass and the energy-utilising activities of the organism. This means that it is easy to overeat beyond our energy needs (eg a diet high in ultraprocessed foods [UPFs]), but weight loss is a threat to the organism and metabolic and appetite plasticities kick in to prevent further weight loss, making prevention a priority.
System models (causal loop diagrams) demonstrate the fundamental characteristics of the most likely driver of the obesity pandemic which is rising in almost all countries and declining in almost none – the profitability of UPF systems. These models show how food systems actors (eg corporate executives, consumers, politicians, food supply chain providers) are intimately part of, and exploited by, the UPF system. Fundamental regulatory constraints are needed on the UPF system to prevent this exploitation.
At the community level, systems approaches can be used to engage local actors in prevention actions targeting the most effective leverage points under their influence. The holistic and relationship-based thinking and participatory processes used in systems approaches (like Group Model Building) are highly concordant with indigenous world views and approaches to action. These hold promise for the food systems transformations we need to prevent obesity.