Both children and adults become fatter because they consume more energy than they expend (Han, Lawlor & Kimm, 2010).

Genetics also plays a role but genetic factors cannot be responsible for the recent epidemic in overweight and obesity (Lindgren et al., 2009).

It is clear that the main emphasis must be on downstream (individual level) solutions and individual responsibility for lifestyle change.

Government recommendations increasingly acknowledge the varied ways individuals can achieve healthy levels of physical activity. However, they tend to emphasise leisure time physical activities, such as sport, running, and going to the gym for adults, and school time activities for children (Hu, 2008; Dobbins et al., 2013).

However, such activity accounts for only a small part of total physical energy expenditure (Hu, 2008). The effect of increasing childhood activity through compulsory physical activity lessons is small and may not result in sustained change.

In recent decades, energy expenditure has decreased markedly because of changes to the urban environment and these include (Frumkin, Frank & Jackson, 2004; Bain, 2006):

• Urban design (which discourages adults from walking to work);
• Safety concerns (which discourage children from walking to school);
• The rise of the car (which causes further concern about the safety of children walking); and
• The near demise of public transport.

Excessive energy intake among individuals is also driven by upstream structural factors. These include the widespread availability of cheap energy dense foods, including vending machines, targeting by the manufacturers of these foods, and ever increasing portion sizes of foods and sugary drinks (Cummins & Macintyre, 2006).

Given these societal influences, it is not surprising that childhood obesity follows similar patterns of transmission to those seen for infectious diseases (Christakis & Fowler, 2007).

This does not mean that we should give up trying to persuade people to change their lifestyles, but it does mean that this is not enough. Interventions aimed at educating people to make healthier choices are generally of limited effectiveness and must be renewed with each generation, which is expensive and time consuming (Ebrahim & Davey Smith, 2001). Such interventions also tend to exacerbate health inequalities.

By contrast, upstream changes are potentially longer lasting and more equitable. Changes to the environment – which make physical activity and a healthy diet once again part of daily life rather than a lifestyle choice – are needed.

References

Han, J.C., Lawlor, D.A. & Kimm, S.Y.S. (2010) Childhood Obesity. Lancet. 375, pp.1737-1748.

Lindgren, C.M., Heid, I.M., Randall, J.C., Lamina, C., Steinthorsdottir, V. & Qi, L., et al. (2009) Genome-wide Association Scan Meta-analysis Identifies Three Loci Influencing Adiposity and Fat Distribution. PLoS Genetics. 5(6): e1000508. doi:10.1371/journal.pgen.1000508.

Dobbins, M., Husson, H., DeCorby, K. & LaRocca, R.L. (2013) School-based Physical Activity Programs for Promoting Physical Activity and Fitness in Children and Adolescents aged 6 to 18. Cochrane Database Systematic Reviews.  2, CD0077651.

Hu, F.B. (2008) Obesity Epidemiology. Oxford: Oxford University Press.

Frumkin, H., Frank, L. & Jackson, R. (2004) Urban Sprawl and Public Health: Designing, Planning and Building for Healthy Communities. New York: Island Press.

Bain, C. (2006) Commentary: What’s Past is Prologue. International Journal of Epidemiology. 35, pp.16-27.

Cummins, S. & Macintyre, S. (2006) Food Environments and Obesity – Neighbourhood or Nation? International Journal of Epidemiology. 35, pp.100-104.

Christakis, N.A. & Fowler, J.H. (2007) The Spread of Obesity in a Large Social Network over 32 Years. New England Journal of Medicine. 357, pp.370-379.

Ebrahim, S. & Davey Smith, G. (2001) Exporting Failure? Coronary Heart Disease and Stroke in Developing Countries. International Journal of Epidemiology. 30, pp.201-205.