Policy Interventions to Tackle the Obesogenic Environment
Hamilton’s meta-analysis of 48 published, community wide campaigns, for example, found an effect on population behaviour in the short term to be an attributable risk difference of 0.09 (i.e. 9% more people adopt the behaviour than did so before the campaign) [143]. Perhaps not surprisingly, larger effects were seen for behaviours that were enforceable by law (e.g. seat belt use=0.17) than for ‘purely persuasive campaigns’ (of the order of 0.05). Larger impacts were also associated with campaigns that had a higher reach (i.e. a larger proportion of the target audience were exposed) and for those that presented new information [142, 143]. Virtually all contemporary media campaigns now include the creation and promotion of websites, the more sophisticated of which also usually include interactive features. Although robust evaluations of web-based campaigns are still relatively rare, they can be a very effective means of achieving a high level of reach and engagement in settings with widespread internet connectedness. The CDC’s ‘VERB’ campaign is a nationwide initiative aimed at increasing physical activity among children aged 9–13 years, which began in 2002 and generated more than 10 million visits to its website [142, 144] over the first two years. Subsequent evaluation of the programme showed an impressive dose-response increase in self reported, free-time physical activity with increasing frequency of exposure to the VERB site (figure 6.2) [145]. Figure 6.2 Median number of free time physical activity sessions (self reported) among children aged 9–13 years in past 7 days, by frequency of exposure to VERB, 2004. *p<0.05
4.2
Medfian # weekly sessions
4.5
4.1
4.2
4.0 3.5
3
3.0
γ=0.09* 2.8
2.5 None
Less than once per week
About once per week
Several times per week
Every day
Frequency of exposures (Source: Huhman et al, 2007 [145]) γ (gamma) statistic for dose response, range: +1.0 (denoting perfect +ve correlation) to -0.1 (denoting perfect negative correlation).
Although VERB results are largely based on self reports, the evaluation is tied to a nationally representative longitudinal cohort survey (Youth Media Campaign Longitudinal Survey [YMCLS]). In addition to correlating activity reporting with campaign exposure as in figure 6.2, the survey also looks at three psycho-social dimensions of physical activity: i. Outcome expectations (i.e. beliefs about benefits) ii. Self-efficacy (i.e. confidence to overcome barriers) iii. Social/family influences (household and peer-group attitudes). The self reported activity data was also cross-correlated with detailed logs for organised and free time activity; the validity coefficients found to be as high as (or higher than), similar seven day recall instruments [145]. The VERB evaluation therefore is sophisticated enough to assess any underlying changes in attitudes, as well as effects on physical activity. Although measurable effects in the first year were confined to free time physical activity in defined sub-populations (e.g. 9 to 10-year old girls),
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