Living near fast-food restaurants and supermarkets hardly has any impact on an individual's body mass index, suggests new research.
Public policies that are designed to reduce the number of fast-food restaurants and increase the number of supermarkets are unlikely to reduce obesity, although such policies may make it easier for people to access healthy foods, according to the study published in the journal Health Affairs.
"Fast food is generally not good for you, and supermarkets do sell healthy food, but our results suggest blocking the opening of a new fast-food restaurant or subsidising a local supermarket will do little to reduce obesity," said Coady Wing from Indiana University in the US.
The research team based its findings on the Weight and Veterans' Environments Study, a comprehensive database stretching from 2009 to 2014 and covering 1.7 million veterans living in 382 metropolitan areas in the US.
The researchers could assess how BMI changed with each veteran and match it with the locations of fast-food outlets and supercenters such as Target and Walmart stores.
The researchers calculated BMI by using height and weight measurements taken when the veterans visited a doctor, nurse practitioner or other provider.
They added up the number of chain fast-food restaurants, supermarkets and other food outlets within one mile and three miles of the person's residence.
With that information, the researchers could track BMI changes, even when a person moved from one area to another or when a fast-food or other outlet opened or closed.
Previous research on this topic has been based on snapshots in time -- known as cross-sectional data -- and had suggested a link between food outlet access and BMI.
"We couldn't find evidence to support policies based on that presumed link," Wing said.