Very low food security among young children is associated with developmental deficiencies. However, little is known about the factors that predict entry into or exit from very low food security during early childhood. This study seeks to, 1) Understand the triggers that explain movements into or out of very low food security among children from birth to age five; and, 2) Examine the first aim using different definitions of food insecurity. The analysis relies on the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B), a longitudinal, nationally representative dataset of approximately 10,700 children, to estimate linear probability models. Results suggest that residential moves and declines in maternal or child health are associated with transitioning into food insecurity, whereas increases in the number of adults in the household are associated with exits from food insecurity. Changes in income and maternal depression are associated with both entrances and exits. These findings are robust to different definitions of food insecurity and model specifications. Findings can help nutrition assistance programs target parents and their children for assistance and information on coping strategies when they are most at risk of experiencing food insecurity.