Searching for Effective Policies in Obesity

From the perspective of public health, we have a tremendous burden of obesity – and it’s growing all over the world. Decades of work to bend the curve of rising prevalence has had no discernable effect. Large and persistent disparities in diet quality mirror disparities in obesity prevalence. We might be good at nudging the population to make a few very specific shifts in dietary behaviors. (Dramatic reductions in sugar consumption come to mind.) But effective policies that actually make an impact on overall diet quality and obesity prevalence are hard to find.

In fact, a new umbrella review of food environment policies tells us:

“Current research largely fails to provide good quality evidence on impacts of food environment policies on socioeconomic inequalities in diets.”

Effectiveness of Taxation?

The new review by Anne Lene Løvhaug and colleagues examines 159 studies of various food policies in six domains. Those domains were composition, labeling, provision, prices, and retailing. In fact, they did find evidence to suggest that taxation might have potential to reduce social and economic disparities in diets.

Certainly, the enthusiasm for tax strategies to shape diet quality across the population is great. A recent analysis of the UK tax on sugar in soft drinks suggests a substantial reduction in caloric intake from those beverages across the population.

But the problem comes when you go looking for data on health outcomes or overall diet quality. On health outcomes, there is simply no data to show a benefit. Mexico has had taxes on sugar sweetened beverages (SSBs) in effect for nearly a decade now. But its problems with diabetes and obesity have only grown worse.

In AJCN,  Pourya Valizadeh, Barry Popkin, and Shu Wen Ng recently looked at linking SSB taxes with fruit and vegetable subsidies. Once again, they did find that taxes can reduce SSB purchases. But they found it was hard to stimulate meaningful increases in fruit and vegetable consumption through subsidies.

Success in Schools

Studies of school-based policies are more encouraging. A recent study of food sources and diet quality for U.S. adults and children found striking improvements in school nutrition.

Other recent encouraging data come from China, published in JAMA Pediatrics. In primary school children Zheng Liu and colleagues conducted a rigorous cluster-randomized study of a school-based obesity prevention program. It used a smartphone app and aimed to involve the whole family. After a year, they found the program reduced obesity prevalence by 27 percent.

Without a doubt, this is remarkable. The remaining big question is whether these results can work at scale in other communities.

Meeting the Challenge

The challenge is daunting. COVID-19 has taught us that, even with effective tools like masks and vaccines, winning public support for health policies can be quite difficult. In obesity, the challenge is even greater because the tools we have are not as potent.

So we have to be clear and objective about this challenge. Only with sufficient determination and curiosity about what will really work can we meet it.

Click here for the review by Løvhaug et al, here for the Valizadeh analysis, and here for the study by Liu et al.

Effects of Good Government in the Countryside, painting by Ambrogio Lorenzetti / WikiArt

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March 8, 2022