From the community to the federal level, concerned citizens and public health professionals have tested various interventions to reduce obesity, from banning super-sized sodas to building fresh food markets in neighborhoods that have little access to healthy foods.
But which of these natural experiments has really made an impact and resulted in improved health?
The answer to that question is not black and white—and it requires rigorous review of the science and methodology of each experiment. Still, we can draw some conclusions about the interventions that show the most promise in helping to slow the obesity epidemic.
A recent systematic review of naturally occurring health- and obesity-related experiments sheds some light on the interventions that had the strongest social impact. The review was led by Stephanie Mayne, a doctoral student, and co-authored by Yvonne Michael, ScD, an associate profession and associate dean for academic and faculty affairs in the Drexel University School of Public Health. The review included PubMed (Medline) articles published from 2005-2013; 1,175 abstracts and 115 papers were reviewed, and 37 studies were included in the review.
The results? Certain types of interventions were more successful than others in reducing obesity-related outcomes. For other interventions, more research is needed.
Here's a summary of the review's findings.
Diet and food policy changes
These interventions showed the strongest impact—and they all had to do with improving the nutritional quality of food offerings:
- Ban on trans fats
- Limits on availability of sugary foods and beverages
- Limits on availability of higher-fat foods
In the research to date, these interventions had a smaller or no impact on obesity:
- Requiring access to nutrition information (Nutrition Facts, ingredients, etc.)
- Supermarkets built in underserved areas
Physical activity changes
This intervention showed the strongest impact on obesity—and results continue to show promise after each long-term follow-up:
- Improving the infrastructure of active transportation (making active transportation—such as walking and biking—easier and safer for people to do)
In the research to date, these interventions had smaller or no impact on obesity:
- Making improvements to parks
- Adding trails
It’s important to note that a common shortcoming of these studies is that they often only measure easier-to-report outcomes, such as the change in foods purchased or change in use of a bike trail. However, rarely do they measure the desired health outcomes, such as weight loss or reductions in chronic disease.
"Research suggests that people will use new amenities like bike shares, and limit purchases of unhealthy foods in specific contexts like schools," said Mayne. "But it is less clear whether these changes translate into overall improvements in diet and physical activity."
What does this teach us?
So you may be asking: Well, what does this teach us then?
The biggest takeaway about reviewing these social experiments is to reveal the current public policies and investments that have the ability to make the biggest a real-world impact on reducing obesity, and to what degree. Regarding food, it appears one of the most successful ways to impact a large population is by improving the nutritional quality of foods offered. Likewise, giving more people access to active transportation options (in my mind, this means things such as making bikes, walking shoes, and safe transportation environments more accessible) had the biggest impact on affecting change in physical activity.
Another takeaway from this review is that it’s not easy or possible to know how obesity interventions can improve the health of a community—but that doesn’t mean we shouldn’t do them. Many people would say that improving even just one person’s health through experimental interventions is reason enough to try it. Others would agree, adding that there’s a trickle-down effect whenever you improve a single person’s health—a phenomenon that stretches over generations, both within and beyond immediate families and social circles. And others would disagree entirely with the concept of obesity interventions, saying that health is more personal—it can’t be forced on anyone.
The authors of this review concluded that more natural experiments are needed to strengthen the evidence about obesity-related policies and interventions. They also recommend more natural experiments to explore whether the timing of a change or repeated exposure to the changed condition enhances or reduces impacts on obesity-related outcomes.
Personally, in my own health journey, having more trails in my neighborhood and having access to calorie counts on menus HAS, to some degree, made an impact on my actions and food decisions (and, perhaps, has moved me farther away from obesity), though this review would say that impact is not widely reflected in society. Perhaps other natural experiments have had more of an impact on you or others in your community, whether you realize it or not. As citizens, one thing we can do is applaud and support natural interventions when we see them happening in our nation, states, and communities—you just never really know who may be affected. Because, like health in general, obesity interventions will probably never be a "one size fits all" model.