A Los Angeles ordinance designed to curb obesity in low-income areas by restricting the opening of new fast-food restaurants has failed to reduce fast-food consumption or reduce obesity rates in the targeted neighborhoods, according to a new RAND Corporation study.

Since the fast-food restrictions were passed in 2008, overweight and obesity rates in South Los Angeles and other neighborhoods targeted by the law have increased faster than in other parts of the city or other parts of the county, according to findings published online by the journal Social Science & Medicine.

"The South Los Angeles fast food ban may have symbolic value, but it has had no measurable impact in improving diets or reducing obesity," said Roland Sturm, lead author of the study and a senior economist at RAND, a nonprofit research organization. "This should not come as a surprise: Most food outlets in the area are small food stores or small restaurants with limited seating that are not affected by the policy."

The policy is a zoning regulation that restricts the opening or expansion of any "stand-alone fast-food restaurant" in Baldwin Hills, Leimert Park, and portions of South Los Angeles and Southeast Los Angeles. The areas subject to the rule have about 700,000 residents. While the rule was not the nation's first local regulation limiting fast-food outlets, it was the first one presented as a public health measure by advocates.

Sturm and co-author Aiko Hattori of the University of North Carolina, Chapel Hill, examined the fast-food ban by analyzing information from two sources. They tracked the opening of new food outlets across the city by reviewing permits issued by the Los Angeles County Department of Public Health, which licenses and inspects all food outlets.

Information about neighborhood eating habits and weight came from three different waves of the California Health Interview Survey, which polls residents across the state about an array of health issues. Participants from South Los Angeles and other neighborhoods targeted by the ordinance were compared to residents from other parts of Los Angeles.

Examining weight trends across the city, researchers found that both obesity and being overweight increased in all areas from 2007 to 2012, with the increase being significantly greater in areas covered by the fast-food ordinance. In addition, fast-food consumption increased in all areas since the ban was passed, but was statistically similar across all areas.

Before the ban was passed as well as three years later, the average body mass index (a ratio of weight to height) and the proportion of people who were obese or overweight were higher in South Los Angeles than in other areas of the city. That gap continued to widen from 2008 to 2012.

"The one bright spot we found is that soft drink consumption dropped, but the decrease was similar in all areas across Los Angeles," Hattori said. "Unfortunately, the rates of overweight and obesity increased and they increased fastest in the area subject to the fast-food ban."

Researchers found that about 10 percent of food outlets in Los Angeles are new since the regulation was approved, but there was no evidence that the composition of those establishments has changed as a result of the ordinance.

New food outlets in South Los Angeles were most likely to be small food stores while new food outlets in other parts of the city were most likely to be larger independent restaurants.

There were 17 new permits for outlets belonging to larger fast-food chains in South Los Angeles from 2008 to 2012, just slightly more than in other parts of the city, but none of them were stand-alone restaurants. The findings show the ordinance has done little to reshape the retail food landscape in the targeted neighborhoods.