Food insecurity disproportionately affects U.S. demographic groups of children and adults at greatest risk for obesity and may lead to weight gain through various pathways. This article presents a comprehensive summary of the current literature on the relationship between food insecurity and weight status, and the role federal food and nutrition assistance programs may play in this relationship. The studies examined suggest that support for an association between food insecurity and weight status among children and men is mixed. Women who experience food insecurity are more likely to be overweight or obese compared to women who are food secure; however there is little evidence that food insecurity promotes increased weight gain over time. Long-term participation in the Supplemental Nutrition Assistance Program may increase risk for excess weight gain.