The U.S. Food Stamp Program may cause weight gain among its users and contribute to a growing obesity problem according to a new nationwide study spanning over 14 years.

Food Stamp Obesity Study

Researchers found that the average user of food stamps had a Body Mass Index (BMI) 1.15 points higher than non-users. The link between food stamps and higher weight was almost entirely based on women users, who averaged 1.24 points higher BMI than those not in the program, the study found. For an average American woman, this would mean an increase in weight of 5.8 pounds. The higher the BMI, the more obese an individual.

The food stamp obesity study also found that:

• people's BMI increased faster when they were on food stamps than when they were not
• peoples BMI increased  the longer they were in the food stamp program

"We can't prove that the Food Stamp Program causes weight gain, but this study suggests a strong linkage," said Jay Zagorsky, co-author of the study and a research scientist at Ohio State University's Center for Human Resource Research.

"While food stamps may help fight hunger, they may have the unintended consequence of encouraging weight gain among women."

In 2008 about 28 million people, or almost 1 in 11 residents, received benefits from the program in a given month. Based on these findings, the Food Stamp Program may have a significant impact on America's obesity rate.

Zagorsky conducted the food stamp / obesity study with Patricia Smith of the University of Michigan-Dearborn. Their study appears in the current issue of the journal Economics and Human Biology.

The researchers used data from the National Longitudinal Survey of Youth, which has questioned the same group of randomly selected Americans since 1979. The NLSY is conducted by Ohio State's Center for Human Resource Research.

In this food stamp / obesity study, Zagorsky and Smith compared nearly 4,000 survey participants who used food stamps with almost 6,000 survey participants who did not. They looked at Body Mass Index (BMI) and food stamp use among the participants from 1989 to 2002.

BMI is one of the most widely used measurements for obesity. The BMI approximates body mass using a mathematical ratio of weight and height.

Obesity has been linked to poverty, so the researchers took into account income and a variety of other factors - including race and education -- that may have also affected the weight of survey participants, outside of the use of food stamps.

In addition, the food stamp / obesity study compared people who lived in the same counties, to take into account that there may be local factors that affect obesity rates.

Even after the various controls, the link between food stamp use and higher weight remained clear, especially for women.

• While female food stamp users in general had an average BMI that was 1.24 points higher than those not in the program, black women's BMI was 1.1 points higher; white women's BMI was 1.96 points higher.

• Male food stamp users, both black and white, did not have significantly higher BMIs than those not in the program.

Additional evidence of food stamps' role in weight gain came when the researchers looked at how people's BMI changed before, during and after they were on food stamps.

• Results showed BMI increased over all three periods, but increased the most when participants were on food stamps.

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

• In addition, the study found the longer participants received food stamps, the higher their BMI.

"Every way we looked at the data, it was clear that the use of food stamps was associated with weight gain," Zagorsky said.

From the data they have, the researchers can't tell for sure why food stamps seem to lead to unhealthy eating practices, Zagorsky said. But there are clues.

Government statistics showed that the average recipient received $81 in food stamps per month in 2002, the last year examined in this study.

"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." That's because calorie-dense, high-fat, processed foods tend to be less expensive than more healthy choices.

Zagorsky said policymakers should aim at changing the types of food that program participants purchase.

"Modifying the Food Stamp Program to include economic incentives to eat healthier might be an important tool for fighting obesity," Zagorsky said.

Those on food stamps could be required to take a course on nutrition. In addition, recipients who purchase fresh fruit and vegetables and other low-fat products could be given more benefits or receive discounts on these products, he said.