Overweight and obesity contribute directly to a variety of adverse health outcomes, as pointed out in a recent Lancet series. At least in high-income countries, these conditions exhibit a pronounced socioeconomic gradient, and therefore present both a challenge and an opportunity. A challenge, because of the complex etiology of overweight and obesity; an opportunity, because of the tremendous improvements in health that can be anticipated from any population-wide shift toward healthy weights.
Two recent syntheses of research findings offer useful insights, and also a few (intentional and unintentional) warnings, about how best to address overweight and obesity. A report by a committee of the US Institute of Medicine got the diagnosis absolutely right, from a health equity perspective: “If a community has no safe places to walk or play, lacks food outlets offering affordable healthy foods, and is bombarded by advertisements for unhealthy foods and beverages, its residents will have less opportunity to engage in physical activity and eating behaviors that that allow them to achieve and maintain a healthy weight.” Unfortunately this valuable analysis was not, in the end, used to arrive at system-level recommendations appropriate to the scale of the problem. The committee described its approach in terms of “large-scale transformative approaches,” but in its proposed responses it drifted back into behavioural nostrums like “mak[ing] physical activity and integral and routine part of life” and “mak[ing] schools a national focal point for obesity prevention” – an example of the phenomenon Jennie Popay and colleagues have described as “lifestyle drift.”
Some environments are far more supportive of maintaining healthy weights than others.
A recent literature review on policy interventions to tackle the obesogenic environment produced by the Scottish Collaboration for Public Health Research and Policy, a research unit headed by expat Canadian John Frank, is more effective at avoiding what I have come to think of as the lifestyle trap. Focused on the situation of working-age adults, the review is organized using a framework called ANGELO (Analysis Grid for Environments Linked to Obesity): a simple four-by-two matrix in which four aspects of the environment – physical, economic, political or legislative, and sociocultural – are each analyzed at two levels, micro (the household or community) and macro (the region, province or nation). The authors make a point that has broad applicability in other population health contexts: “[M]any strategies aimed at obesity prevention may not be expected to have a direct impact on BMI, but rather on pathways that will alter the context in which eating, physical activity and weight control occur. Any restriction on the concept of a successful outcome … is therefore likely to overlook many possible intervention measures that could contribute to obesity prevention.”
The authors of the review are candid about the difficulties facing large-scale interventions that are expensive or challenge vested interests, yet do not shrink from asking tough questions about the need for these, noting (for example) that the transport mode split in urban areas is 84% by car versus 9 percent walking in the United States, while it’s 36% by car versus 39% walking in Sweden. “Suffice it to say, it has been a concerted combination of infrastructure provision, integrated transport planning and disincentives for private cars which has helped to bring about the higher active travel rates,” which include a much larger role for cycling as well. And they argue that because of the relatively high price elasticity of soft drink taxation, it should be considered as a promising intervention along with price reductions of healthy foods like fruit and vegetables. (As an aside on a related point, I once heard a leading aboriginal health researcher wonder why Ontario can ensure that a bottle of whisky costs the same in the province’s far north as in downtown Toronto, but can’t or won’t do this for a carton of milk or a bag of apples.)
A further step in the Scottish review was to create another matrix classifying potential interventions on two criteria: certainty of effectiveness and potential population impact. Here a sugared beverage tax scored high on both criteria, as did healthy eating advocacy campaigns backed with supportive regulation, although curiously none of the policies that have been adopted to increase the costs of car travel scored similarly high, despite the authors’ extensive documentation of the role of public policy and their warning about defining successful outcomes too narrowly. But this is a minor disagreement with an important research synthesis on a complex problem that also provides a methodological template for reviews in other areas. It should be read by everyone concerned with social determinants of health, even if not specifically with overweight. Health policy analysis has joined other, more familiar high quality products for which Scotland is justifiably known far beyond its borders.
Not the only quality product of Scotland.