Food stamps and obesity - what do we know?

Food stamps don't make recipients fat, except perhaps for "non elderly" women. Those are the quick finding of this USDA ERS study on food stamps and obesity. From the report summary:


Results from the reviewed studies indicate that for the majority of program participants— children, nonelderly men, and the elderly—use of food stamp benefits does not increase either Body Mass Index (BMI) or the likelihood of being overweight or obese. For some subgroups, food stamp participation has a negative association with the probability of overweight. Nonelderly adult women, who account for 28 percent of the food stamp caseload, are the only group of food stamp recipients for whom multiple studies show a link between food stamp receipt and elevated BMI and obesity. According to these studies, food stamp participation over a 1- or 2- year period increases the probability of a woman’s becoming obese by 2 to 5 percentage points and may lead to a 0.5-point increase in BMI, or about 3 pounds for a woman 5’4” to 5’6” tall. The length of time one participates in the Food Stamp Program may have an impact on obesity. The reviewed studies found that long-term participation among nonelderly women was linked to a higher probability of obesity by 4.5 to 10 percentage points. One study also found a smaller, but positive relationship between long-term food stamp articipation and obesity for men. These results may suggest that small changes in BMI due to food stamp use accumulate over longer “spells” of participation. But enough is not known about the causal mechanisms of participation and weight gain to conclude that long-term use of food stamp benefits causes weight gain. Long-term food stamp participants are likely to be different from short- and medium-term participants in ways that one cannot observe. It is also unclear why food stamp participation may affect women, but not men or children. Factors that may accountfor this effect include differences in energy requirements, activity levels, or household allocation of resources. Some evidence indicates that food stamp participation, food insecurity, and weight status are related. One study shows that weight change over a 2-year period among women who were persistently food insecure was less than that for women who were persistently food secure. But, food stamp participation roughly offset the smaller weight change for those who were persistently food insecure—a result consistent with the program’s serving as a nutritional buffer during difficult economic times. The reviewed studies were faced with separating and measuring two distinct relationships. On the one hand, food stamp participation may result in obesity. On the other hand, individuals who are heavier may be the very people who are more likely to apply for food stamps, because of larger appetites, for example. Causal attribution is a major challenge for these studies. Methodological and data weaknesses limit the ability of analysts to be certain that increased BMI and obesity risk are due to food stamp participation. Differential effects across sex and age groupings are also unexplained. The Food Stamp Program is a household-level program, and 89 percent of food stamp benefits go to households that
contain a child, elderly adult, or nonelderly disabled adult. Devising program changes that are appropriately targeted to household members who may be at risk of gaining weight, without harming those who are not and who need the nutritional assistance, presents a difficult challenge. Policy changes that help improve overall diets of all household members may be more effective.