Food insecurity has been associated with overweight status in women. A number of hypotheses have been proposed to explain this association, some of which assume that household food insecurity is a cause of overweight. Similar to food insecurity, Food Stamp Program (FSP) participation has been associated with overweight status in women. One longitudinal study has also found a small effect of program participation on obesity status in women. Modeling FSP participation without accounting for the effect of need to participate in the program, as estimated by household food insecurity status, may lead to confounded findings. To estimate the direction and timing of the relation between food insecurity, this study reports on recently available longitudinal data from the Panel Study of Income Dynamics. The major finding of this paper is that persistent food insecurity was associated with a smaller weight change, controlling for other income and health-related risk factors for weight change. Among persistently food-insecure women, full participation in the FSP offset the weight change. There were no significant associations between change in food insecurity status and weight change in these data.