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."