Although public health research draws heavily on health psychology, it goes beyond the analysis of individual behaviours to include aspects of their social contexts such as families, institutions, communities, local environments, national policies, and social norms. At DECIPHer, we use a socio-ecological model, which theorises health behaviours as occurring within social contexts at different levels. We take an interdisciplinary perspective; researchers come from many different fields including psychology, sociology, social policy, education, sports science and geography, and we use a wide variety of theories and methods in our research.
In a recent DECIPHer seminar in Cardiff, we discussed how public health research has looked outwards from the individual to various levels of social contexts, but in taking this perspective has lost sight of the human body to some extent. The role of biochemistry, physiology and neurological development are not often discussed in the public health literature or incorporated into intervention designs, yet these are fundamental aspects of human biology which are closely related to health behaviours.
For the seminar, we read a recent paper on obesity, which argues that public health interventions for obesity do not draw on recent findings in the natural sciences on the biological processes and biochemical aspects of weight loss. The paper claims the simple weight loss model used by many public health interventions, based on energy balance (i.e. taking in fewer calories than you burn) is out of date. It argues that weight loss is regulated in the body by complex ‘homeostatic feedback’ mechanisms. These are processes by which various aspects of the body’s metabolism can inhibit weight loss – for example, hormonal or neural processes may increase hunger or fatigue, which drive a tendency to eat more and exercise less. These mechanisms have particular significance for maintaining any weight loss long-term as they tend to counter initial weight loss.
The paper also discussed the ‘hyperpalatability’ of foods high in sugar and fat, and how these may interact with different aspects of appetite and eating behaviour at a biological level through levels of sugar, insulin and lipids in the bloodstream. Restricting carbohydrates, for example, may produce better insulin control and in doing so contribute to weight loss more effectively than weight-loss strategies based solely on energy balance.
Some areas of public health research draw more on the natural sciences than others. One area where biology has had some attention is health inequalities. For example, the relationship between poverty, stress and cortisol, where poverty is associated with increased cortisol levels (an indicator of physiological stress), is an established link between biology and social environment. Additionally, a recent editorial in the BMJ discusses the relationship between poverty and the reduced functioning of the part of the brain responsible for resisting impulses. This has implications for health behaviours, such as greater difficulty in resisting unhealthy food. This may exacerbate problems of living in deprived areas where opportunities to eat unhealthily (through higher densities of fast food outlets) are greater.
An interesting TED talk by neuroscientist Professor Sarah-Jayne Blakemore highlights how brain development is related to impulsivity and decision-making. It was once thought that early childhood was a critical time for learning but as Prof. Blakemore highlights in her talk, research is showing that adolescence is a time of fine-tuning skills. The environments people find themselves in shape the skills that are learnt during this period. Adolescence is therefore an excellent opportunity to nurture adolescent decision-making and improve healthy adolescent development.
This is not to say that we should revert to a model of health improvement that focuses only on the individual. Health behaviours are also dependent on many other factors, including an individual’s environment. For example, a teenager might be more likely to engage in alcohol use because of changes in the brain associated with puberty. However, the ability of a young person to engage in alcohol use will also depend on environmental and social factors such as parental supervision and access to alcohol in the first place (for more on this, see the section titled implications for prevention in Steinberg’s article about adolescent risk-taking).While a few examples of integration with the natural sciences can be identified in public health research, this is still somewhat piecemeal and no common frameworks or models exist in the public health literature. However, an example of combining biological and psycho-social perspectives does exist in the healthcare field in the US. The biopsychosocial model is a multi-level model that encompasses biological aspects of disease, psychological factors and the social environment, and takes into account how these different aspects might interact. It can be applied in drug rehabilitation, for example, to address the biochemical processes of withdrawal from substance misuse while at the same time resocialising individuals through healthy relationships and a drug free environment.
This biopsychosocial model functioned as a corrective to earlier medical models, which privileged biological aspects of disease over social factors. Combining a biopsychosocial model with the socio-ecological perspective into a ‘bio-psycho-socio-ecological’ model could reorient public health research inwards towards the biology of the human body as well as outwards to the social, environmental and structural levels, resulting in a more extensively interdisciplinary and multi-level approach to health behaviour research.