BACKGROUND Due to the pandemic of child and adolescent overweight and obesity, improvements in overweight and obesity treatment availability and accessibility are needed. METHODS In this prospective study, we investigated if reductions in body mass index (BMI) standard deviation scores (SDS) and waist circumference (WC) would occur during 1.5 years of community-based overweight and obesity treatment based upon an effective hospital-based overweight and obesity treatment protocol, The Children's Obesity Clinics' Treatment protocol. Height, weight, and WC were measured at all consultations. Changes in BMI SDS and WC were analyzed using linear mixed models based upon the repeated measures in each child. RESULTS From June 2012 to January 2015, 1,001 children (455 boys) were consecutively enrolled in the community-based treatment program. Upon entry, the median age was 11 years (range: 3-18), and the median BMI SDS was 2.85 (range: 1.26-8.96) in boys and 2.48 (range: 1.08-4.41) in girls. After 1.5 years of treatment BMI SDS was reduced in 74% of the children. BMI SDS was reduced by a mean of 0.38 (95% confidence interval (CI): 0.30-0.45, p<0.0001) in boys and 0.18 (95% CI: 0.12-0.25, p<0.0001) in girls after 1.5 years of treatment, independently of baseline age, BMI SDS, and Tanner stage (all p>0.08). WC was reduced by a mean of 3.8 cm (95% CI: 2.7-4.9, p>0.0001) in boys and 5.1 cm (95% CI: 4.0-6.2, p>0.0001) in girls. The dropout rate was 31% after 1.5 years. A median of 4.5 consultation hours was invested per child per year. CONCLUSION BMI SDS and WC were reduced after 1.5 years of treatment. Hence, this community-based overweight and obesity treatment program may help accommodate the need for improvements in treatment availability and accessibility.