This report presents the findings of a natural experiment research design to study the effect of food stamps on body mass index (BMI) of adults in low-income immigrant families. To accomplish this, the study uses changes in immigrant eligibility for the Food Stamp Program (FSP) caused by the 1996 Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA) and State responses to the Federal law.
The 1996 Federal law denied immigrants access to food stamps, resulting in a sharp decline in their FSP participation. In response to PRWORA, some States started substitute FSPs to provide benefits for new immigrants and those who had entered the country before the enactment of the Federal policy. (Federal law subsequently restored FSP eligibility to certain groups of pre-PRWORA arrivals.)
The study hypothesizes that, if FSP participation leads to obesity, the prevalence of obesity among immigrants should decline in the post-PRWORA period in States that implemented the Federal law compared with States that instituted substitute FSPs. Further, the use of food stamps by post-PRWORA arrivals also declined. Again, if FSP participation causes obesity, the decline in obesity should be greater among newly arrived immigrants compared with pre-PRWORA immigrants.
The study uses the National Health Interview Survey (NHIS) and the March Current Population Survey (CPS) and applies a two-sample instrumental variables research design to estimate the association between FSP participation and BMI of foreign-born adults. Federal and State changes to immigrant FSP eligibility in 1996 are used as instrumental variables to predict FSP participation.
The empirical analysis suggests that, in the post-1996 period, food stamp use by foreign-born unmarried mothers with a high school or lower education was 10 percentage points higher in States with substitute programs than in States that implemented the Federal restrictions. However, this increase in FSP participation was not associated with any statistically significant difference in BMI among low-educated, foreign-born unmarried mothers.