Context: While food insecurity and obesity have been shown to be positively associated in women, little is known about the direction of the causal relationship between these 2 constructs. Purpose: To clarify the direction of the causal relationship between food insecurity and obesity. Methods: Chi-square and logistic regression analysis of data from a cohort of 622 healthy childbearing women living in a 10-county rural area of upstate New York and followed from early pregnancy until 2 years postpartum. Findings: Obesity in early pregnancy was associated with increased risk of food insecurity at 2 years postpartum. Initial food insecurity was not associated with increased risk of obesity at 2 years postpartum. Women who were both obese and food insecure in early pregnancy were at greatest risk of major weight gain over the pregnancy and postpartum period. Conclusions: Obesity appears to lead to food insecurity rather than the converse. Obesity combined with food insecurity present the greatest risk for major weight gain in this sample of childbearing women.