BackgroundMulticomponent lifestyle interventions are fundamental in pediatric obesity management. However, whether household food insecurity influences the efficacy of such interventions remains undocumented. ObjectivesThe objective was to compare changes in BMI z-score (BMIz) among children whose family received lifestyle counseling at a pediatric obesity management clinic in Montréal (Canada) according to their household food security status. MethodsThis is a retrospective, longitudinal analysis of medical records of children (2–17 y) with overweight or obesity who received lifestyle counseling at a pediatric obesity management clinic. The number of visits at the clinic and the duration of the follow-up were individualized. Household food security status was assessed using the Health Canada’s Household Food Security Survey Module at the first visit at the clinic. BMIz was calculated and updated at each visit. A reduction of ≥0.25 in BMIz between the last and the first visit at the clinic was considered clinically meaningful. Statistical significance was considered at P < 0.05. ResultsAmong the 214 children included in the study, 83 (38.8%) lived in a food insecure household. In multivariable-adjusted analyses, differences in BMIz between the last and the first appointment tended to be smaller among children who lived in a food insecure household than those in children living in a food secure household [ΔBMIzfood insecurity = −0.432 (95% CI: −0.672, −0.193) compared with ΔBMIzfood security = −0.556 (95% CI: −0.792, −0.319; P = 0.14)]. Differences were most notable in the first 6 mo of follow-up. The OR of achieving a clinically significant reduction in BMIz over follow-up associated with household food insecurity, compared with household food security, was 0.57 (95% CI: 0.31, 1.05; P = 0.07). ConclusionsIn this sample of children followed up at a pediatric obesity clinic, those who lived in a food insecure household experienced smaller BMIz reductions than those who lived in a food secure household.