There’s more to be gleaned from national health surveys than just health statistics. Not only can these data illustrate the scope of a public health problem such as obesity, but they can also provide researchers with clues about ways to intervene. Parke Wilde, PhD, a food economist at the Friedman School of Nutrition Science and Policy at Tufts University, and a co-author recently analyzed data from the continuous National Health and Nutrition Examination Survey (NHANES), a nationally-representative survey of more than 10,000 Americans. Their findings not only confirm the seemingly counterintuitive relationship between weight and income, but suggest that, for women, the risk of weight gain over time is increased when access to food is uncertain or inconsistent.

“To my knowledge, this is the first study to focus on the association between adults’ food security status and change in weight over time, using national level data,” Wilde says. Household food insecurity is defined as “the lack of access to enough food for household members at all times in socially acceptable ways.” Wilde believes this research may have implications for federal food assistance and nutrition programs designed to improve nutrition and household food security for low-income Americans.

The team analyzed NHANES data from 1999 to 2002, accounting for factors that might influence both weight and food security status, such as income, race/ethnicity, education level, and health status. Survey respondents were classified into four levels of household food security, ranging from fully food secure to food insecure with hunger. With the exception of those living in households with the most severe level of food insecurity, women in food-insecure households were approximately 50 percent more likely to be obese and to gain at least 10 pounds in one year, compared with women in fully food-secure households. These relationships were similar for men, but not as pronounced as they were for women.

One hypothesis for why there is a contradictory relationship between weight and income, Wilde says, is that, “gradual weight gain may occur from inconsistent access to food, leading to periods of underconsumption followed by compensatory overconsumption. Alternatively,” he adds, “when money is less available, people may consume inexpensive, high-calorie foods.”

According to Wilde, changes to some food assistance programs might reduce the problem. “Food stamps are available in monthly cycles. This may lead to uneven purchasing and consumption. Perhaps the federal Food Stamp Program could be modified to provide benefits more frequently to even the distribution. This possibility is worth investigating.” Wilde also suggests ways that nutrition education programs can be used to help discourage consumption patterns that promote obesity.  For example, he says, USDA’s Expanded Food and Nutrition Education Program (EFNEP), might be able to teach low-income families strategies to manage their resources in such a way that consumption is more stable over time.

“Our results for weight change bolster the circumstantial evidence that intermediate levels of household food insecurity contribute to weight gain and risk of obesity,” says Wilde. “However, firm causal claims cannot be made using our research,” he cautions. “Further research is needed to better establish that cyclic purchasing leads to cyclic consumption patterns, and that the cyclic consumption patterns lead to gradual weight gain over time.” Wilde proposes, “If we can identify economic factors that increase the risk for obesity among low-income Americans, we can work to modify some of these risk factors.”

Wilde PE, Peterman JN. Journal of Nutrition. May 2006; 136(5): 1395-1400.  “Individual weight change is associated with household food security status.”

Tufts University Health Sciences