England has one of the highest childhood obesity rates in Europe. To promote a healthier food environment in 2015, Gateshead Council in North East England introduced planning guidelines effectively banning any new fast-food outlets. Our aim was to investigate whether this policy led to any reductions in childhood overweight and obesity prevalence and the inequalities in these outcomes. We used data from the National Child Measurement Programme, the Food Standards Agency Food Hygiene Rating Scheme data, and the Office of National Statistics between 2012 and 2020. We estimated a difference-in-differences model employing propensity score matching to identify a control group. We found no significant change in population-level childhood overweight and obesity in Gateshead compared with control areas. In subgroup analysis by area-level deprivation, we found that the quintile of deprivation with the highest proportion of fast-food outlets had a statistically significant reduction of 4.8% in the prevalence of childhood overweight and obesity compared with control areas. Restricting fast-food outlets in areas with a high concentration of such outlets as part of a package of policies to reduce childhood obesity may help to reduce prevalence and inequalities in childhood overweight and obesity.