Packing on the pounds may be an unintended consequence of the U.S. Food Stamp Program, according to research that shows that getting food stamps may help contribute to obesity, at least among women.

We can't prove that the Food Stamp Program causes weight gain, but this study suggests a strong linkage, Jay Zagorsky, a research scientist at Ohio State University's Center for Human Resource Research, Columbus, noted in a university-issued statement.

Food stamps, the major U.S. anti-hunger program, help poor people buy groceries.

Zagorsky, along with Patricia Smith of the University of Michigan in Dearborn, studied weight changes over 14 years in nearly 4,000 people in the food stamp program and almost 6,000 not in the program.

They found that the typical female user of food stamps was heavier than the non-user, after taking into account a variety of factors that might influence body weight.

Specifically, the researchers calculated body mass index, or BMI, a measure of weight in relation to height used to gauge how fat or thin a person is. Female food stamp users, they found, had a BMI 1.15 points higher than a similar woman who did not participate in the food stamp program.

For the average American woman standing 5 feet 4 inches tall this means an increase in 5.8 pounds of body weight.

Zagorsky and Smith also found that BMI increased faster when participants were getting food stamps than when they were not, and increased more the longer they were in the food stamp program.

The average food stamp users saw their BMI go up 0.4 points per year when they were receiving food stamps, compared to 0.07 points per year before and 0.2 points per year after they no longer received food stamps.

While food stamps may help fight hunger, they may have the unintended consequence of encouraging weight gain among women, Zagorsky said in the statement. Every way we looked at the data, it was clear that the use of food stamps was associated with weight gain, he added.

While this association does not prove that the Food Stamp Program causes weight gain, it does suggest that program changes to encourage the consumption of high-nutrient, low-calorie foods should be considered, Zagorsky and Smith note in the latest issue of Economics and Human Biology.

In 2008, roughly 28 million people -- or almost 1 in 11 Americans -- received benefits from the food stamp program in a given month.

Food stamp participants, the researchers say, may choose cheap, calorie-dense, high-fat, processed foods over healthier, more expensive food, maybe because food stamps don't provide enough money to buy healthy foods, Zagorsky contends.

In 2002, the average recipient received $81 in food stamps per month. That figure was shocking to me, Zagorsky said. I think it would be very difficult for a shopper to regularly buy healthy, nutritious food on that budget.

Modifying the food stamp program to include economic incentives to buy and eat healthier foods might be an important tool for fighting obesity, Zagorsky offers.

People on food stamps, for example, could be required to take a course on nutrition and food stamp users who purchase fresh fruit and vegetables and other low-fat products could be given more benefits or receive discounts on these products, he said.

SOURCE: Economics and Human Biology, 2009.