Turns out, limiting the access to fast-food restaurants is unlikely to reduce obesity.

The Indiana University researchers used results from the largest national study ever conducted of the connection between residential environments and body mass index (BMI)."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 subsidizing a local supermarket will do little to reduce obesity," Researcher Coady Wing said.The study also found that changes in the availability of fast-food restaurants and supermarkets near a person's home are not associated with reductions in BMI.

There is no evidence that relationships between BMI and food outlets are different in neighbourhoods with higher poverty levels.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.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.

"We couldn't find evidence to support policies based on that presumed link," Wing said. "Strategies like the healthy food financing initiatives some cities are pursuing could have benefits, for example reducing the saturation of unhealthy food sources in impoverished neighbourhoods. But those policies alone aren't likely to lead to healthier BMI."The study appears in the journal Health Affairs.