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NEW YORK (Reuters Health) - Black and less-educated people tend to cut back on their fast food purchases when prices rise more than other consumers, according to a new study.
Low fast food prices were linked to worse health - including higher weights - among those participants in particular, researchers found.
"We were very interested in understanding whether fast food prices might influence fast food behavior, so if prices were high, did that reduce the number of visits to fast food restaurants," senior author Penny Gordon-Larsen told Reuters Health in an email.
Gordon-Larsen is a nutrition researcher with the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill.
"We were surprised to see differential effects by sociodemographic factors - such that lower socioeconomic status individuals and blacks seemed to show stronger sensitivity to prices," she said.
That suggests policies that affect fast food prices "might have comparatively greater influence on the groups at highest risk for diet-related chronic diseases," she added.
Most studies on this topic have been small or looked only at one point in time, Gordon-Larsen said. For their report, published in JAMA Internal Medicine, she and her colleagues examined changes in fast food prices and health over two decades.
They used data from a long-term study of 5,115 young adults living in one of four large U.S. cities.
Participants reported on their fast food consumption and underwent physical exams in 1985 when the study began and after seven, 10, 15 and 20 years. A total of 3,537 of them completed the study in 2006.
The researchers also tracked fast food price information that included data on pizza, cheeseburgers and fried chicken from national chains during that span. They adjusted prices for inflation.
Over the 20-year period, overall fast food consumption declined, as did fast food prices.
Black people and those with less education tended to eat fast food more often than other consumers. But they were also more sensitive to price increases.
For instance, when fast food cost $1.25 per serving, black people ate it 2.20 times per week and white people ate it 1.55 times per week, on average.
When prices rose to $1.53 per serving, black people dropped their fast food consumption to 1.86 times per week. White people held relatively steady at 1.50 fast food meals per week.
The researchers also noticed a connection between fast food prices and health. Lower prices were linked with heavier weights among black and less-educated participants and higher rates of insulin resistance (a precursor to diabetes) among less-educated and middle-class participants.
"Fast food has been getting cheaper," Dr. Mitchell Katz, a deputy editor for the journal, writes in an accompanying note.
"As the authors show, when fast food is cheap, people choose it more often. Blacks and persons with less education were more sensitive to fast food price, indicating that low cost fast food may be contributing to disparities in obesity rates," he adds.
SOURCE: bit.ly/IZGqPC JAMA Internal Medicine, online January 13, 2014.