The CLAHRC WM Director spotted an article on obesity prevention in a recent issue of the Economist. It was based on a systematic review and quantitative analysis of the literature covering 74 anti-obesity interventions, classified into four groups according to the mechanism of action. The main findings are very much in line with current opinion:
- Highest impact interventions rely on restricting choices (through regulation or structuring the environment differently), rather than individual will-power.
- Structural solutions, such as provision of healthy food at schools, apply to wider populations and tend to be more enduring than those targeting behaviour on individual / small group basis.
- However, there is no magic bullet and investing in the lower impact measures is still worthwhile; we cannot rely only on regulation and structural solutions, and a number of CLAHRCs are investigating methods to change individual behaviour.
- Strategies relying on conscious effort have ephemeral effects, but some more so than others. Exercise alone is least effective in reducing weight in the short-term and these minimal effects are not enduring. Diet and exercise is more effective than diet alone in the short-term, but they end up about the same (mean weight loss of 5kg) at 50 months. Of course, exercise has benefits apart from weight-loss.
- Advertising campaigns that address social norms and self-image are particularly effective in primary prevention – for example, stigmatising drunk drivers. However, the CLAHRC WM Director thinks that such messages would have to be carefully framed to avoid “victim blaming” in the context of obesity.
The authors have a provocative message for researchers that is relevant to the prevention themes within CLAHRCs. They make two points:
- It is difficult to measure the effect of some interventions, such as making cycle lanes available.
- Some worthwhile effects are very small and hence hard to measure.
These are important points to which the Director makes the following responses:
- It is crucially important not to conflate “no evidence of effect” with “evidence of no effect” – a lack of precise and accurate evidence is, by itself, a prescription for neither action nor inaction.
- Evidence of take-up of healthy behaviour can be used to model downstream effects and hence can help in deciding whether, on balance, a certain intervention is worthwhile. It is possible to model, for example, the potential effects on health of cycle lanes on the basis of changes in cycling behaviour.
- Because such models must be populated with a wide range of parameters, many of which are very uncertain, Bayesian methods should be used to calibrate effects and their credible ranges.  
- It is possible that the effect of introducing a wide range of interventions in parallel is more than the sum of each individual intervention effect. To put this another way, multiple interventions across society may generate a change in attitude – a culture change.
— Richard Lilford, CLAHRC WM Director
- The Economist. The War on Obesity: Heavy Weapons. The Economist. 2014.
- McKinsey Global Institute. Overcoming Obesity: An Initial Economic Analysis. New York, NY: McKinsey & Company. 2014.
- Yao GL, Novielli N, Manaseki-Holland S, Chen YF, van der Klink M, Barach P, Chilton PJ, Lilford RJ; European HANDOVER Research Collaborative. Evaluation of a predevelopment service delivery intervention: an application to improve clinical handovers. BMJ Qual Saf. 2012; 21 (s1): i29-38.
- Lilford RJ, Chilton PJ, Hemming K, Girling AJ, Taylor CA, Barach P. Evaluating policy and service interventions: framework to guide selection and interpretation of study end points. BMJ. 2010; 341: c4413.
- Lilford RJ, Girling AJ, Sheikh A, Coleman JJ, Chilton PJ, Burn SL, Jenkinson DJ, Blake L, Hemming K. Protocol for evaluation of the cost-effectiveness of ePrescribing systems and candidate prototype for other related health information technologies. BMC Health Serv Res. 2014. 14: 314.