PUBLIC HEALTH
March 24, 2015

Lessons from The Battle on the Bulge

Cities have banned super-sized sodas and built bike lanes. What works?

What makes a difference when it comes to curbing the obesity epidemic? Public health officials around the world have enacted a number of policy changes in an effort to help people eat less and move more. But do they work?

There are now communities which require calorie counts and nutritional information on restaurant menus, and others which encourage cafeterias to offer healthier, lower calorie, food choices. Some cities have focused on adding activity to the environment, with walking paths and bike lanes, banned certain foods and beverages, and added grocery stores to areas considered food deserts.

It is not easy to figure out what sorts of programs and policies actually help people lose weight.

What changes really have an effect on obesity? Researchers at Drexel University reviewed the results to date. What they found is preliminary — in many cases more years are needed to adequately measure the long-term benefits on health — but they do suggest things we can all do to reduce our risk of gaining weight and even increase our chances of losing it.

Act Naturally

It is not easy to figure out what sorts of programs and policies actually help people lose weight. Not only are the various health efforts monitored differently, they gather different kinds of information. Few, for example, weighed citizens or checked body mass (BMI) before and after implementing new public health initiatives.

The Drexel researchers focused on “natural experiments.” Did people lose weight after a policy like banning the sale of extra-large cups of sugar-sweetened soda was put into effect? Did calorie consumption or the activity level of a population change after bike lanes were built?

The researchers combed through nearly 1,200 abstracts to find policies and changes to the built environment that had been evaluated using natural experiments, and selected 37 studies from which they were able to identify the types of changes that were more successful in reducing obesity, as well as areas where further research is needed before conclusions can be drawn.

Policies that Work

They found a few programs that did help in the battle of the bulge. The food policy changes that had the biggest effect on improving diet were banning trans fats, limiting the availability of sugary foods and beverages and high-fat foods, and altering purchase/payment rules for low-income food vouchers.

Surprisingly, requiring that nutrition information be provided to consumers or adding grocery stores to underserved areas appeared to have little to no impact on citizens' weight.

Certain changes to the environment — policies that encouraged active transportation like building bike paths and bike sharing — had the strongest impact on physical activity. Other changes like park improvements and adding more trails may also be effective, but they require more time, and funding, to accurately determine their effects.

More Information Needed
One reason it was difficult to get a complete picture of the effects of different interventions is that they often didn't measure the desired health outcomes, like weight loss. Instead, the studies recorded how many people used a park or how many fruits and vegetables were purchased, so it was not possible to firmly conclude their effects on obesity. It's not that they don't necessarily help, just that there isn't enough information to know for sure.

The food policy changes that had the biggest effect on improving diet were banning trans fats, limiting the availability of sugary foods and beverages and high-fat foods.

In general, studies with longer follow-up periods after a policy change or intervention was enacted had better results, but the authors concluded that there isn’t yet enough evidence to say whether environmental and policy changes actually help people lose weight. Again, this doesn't indicate they don't work, just that more data are needed.

Natural experiments can help us see what types of public policies and capital investments make a real impact on the health. More of these types of experiments are needed to add to the knowledge base about obesity-related policies and interventions, the authors conclude.

The study is published in Obesity Reviews.

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