The research, published in Obesity Reviews, systematically analysed information from 37 previously published studies of ‘natural experiments’ that looked at people's calorie consumption or physical activity levels either comparing before and after a policy or environmental change, or comparing against a similar group of people not affected by that change.
Led by Stephanie Mayne from the Drexel University School of Public Health, the research team reported that nutrition-related studies found greater effects because of bans/restrictions on unhealthy foods, mandates offering healthier foods, and altering purchase/payment rules on foods purchased using low-income food vouchers compared with other interventions (menu labelling, new supermarkets).
“Our results suggest that certain types of interventions have more success than others in improving outcomes of interest. For example, a majority of studies evaluating regulations that required improvements to the food environment, either through local or school policies found improvements in purchasing or self-reported diet, while studies that simply required the posting of nutritional information found little effect, with a few exceptions,” wrote the team.
Mayne and her colleagues noted that a common shortcoming in many studies is that they only measured process outcomes such as food purchases, rather than measuring the desired health outcomes, such as weight loss.
Indeed, only three studies directly assessed body mass index or weight, leading to a conclusion that top-level evidence is still lacking on whether environmental and policy modifications are successful in maintaining healthy weight or reducing excess weight.
Systematic review
The Drexel team reviewed the state of the science on this topic, evaluating the results and methods of previous studies published in the medical literature between 2005 and 2013.
In this time, the authors found 1,175 abstracts, of which 115 papers were reviewed and ultimately 37 studies were included in the review.
According to the findings, changes with strong impacts were ones that improved the nutritional quality of foods, including trans-fat bans, limiting the availability of sugary food and beverages, and limiting the availability of higher-fat foods.
Meanwhile, changes that had smaller or no impacts in the research to date included building supermarkets in under-served areas and enforcing nutritional information requirements.
Policies that improved the ability of low-income people to use benefits to purchase fruits and vegetables found improvements to purchasing or home availability of healthy food, the team added.
Source: Obesity Reviews
Published online ahead of print, doi: 10.1111/obr.12269
“Impact of policy and built environment changes on obesity-related outcomes: a systematic review of naturally occurring experiments”
Authors: S. L. Mayne, A. H. Auchincloss, Y. L. Michael