Once considered primarily a problem of the poor, obesity is growing fastest in among those making more than $60,000 a year, according to a study presented at the American Heart Association’s 45th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
“There has been a perception that poor people are more likely to be fat,” said presenter Nidhi Maheshwari, M.B.B.S., a graduate research assistant in epidemiology in the University of Iowa College of Public Health at Iowa City. “However, obesity is growing at a much faster rate in those with the highest incomes.”
The researchers compared data collected in the National Health and Nutrition Examination Surveys in 1971-74 and 2001-02. It included data from Americans ages 20 years and older in five surveys, and defined obesity as a body mass index, derived from a formula that accounts for height and weight, of 30 or above. Researchers used a mobile van to reach the neighborhoods to measure individuals’ heights and weights.
Family income was adjusted to 2,000 U.S. dollars and was divided into income quartiles of below $25,000, $25,000-$39,999, $40,000-$60,000, and above $60,000. The same income categories were used for both surveys.
They found that the highest income category, above $60,000, had the greatest increase (276 percent) in obesity prevalence from 9.7 percent in 1971-1974 to 26.8 percent in 2001-2002. Obesity prevalence in those making less than $25,000 was 22.5 percent in 1971-1974 and was 32.5 percent in 2001-2002, an increase of 144 percent. For those earning $25,000-$39,999, the prevalence was 16.1 in 1971-1974 and 31.3 in 2001-2002, a 194 percent increase. For those earning $40,000-$60,000, the increase was about 209 percent.
“The inverse relationship between income and obesity seen in earlier studies has eroded,” said co-author Jennifer G. Robinson, M.D., M.P.H., associate professor of epidemiology in the University of Iowa. “Obesity prevalence now is similar across all income categories, with obesity prevalence in the highest income group rapidly approaching that of the lowest income group.”
“The rich became a whole lot richer, pulling up the average income,” she said. “Interestingly, there are more in the lowest income group as well.”
Different dynamics are associated with the rise in obesity, she said. “The fact is that obesity is increasing in all races, all income categories and at a faster rate with people in higher incomes. While factors are common to both the rich and the poor, there may be certain factors primarily affecting the poor, and a different set of reasons primarily affecting the rich.”
Other researchers include Neal Kohatsu, M.D., M.P.H., and Bridget Zimmerman, Ph.D., University of Iowa, IowaCity, Iowa.