Background: The aim of this study was to test a weight loss program for young people based on an addiction treatment approach. Methods: A pilot study (n=43) was conducted of a 20-week child/adolescent obesity intervention based on an addiction treatment model (staged, incremental withdrawal from problem foods, snacking/grazing, and excessive amounts at meals) and implemented by a server-integrated smartphone app with health professional support. The primary outcome was standardized %overBMI measured at four time points. Secondary outcomes were participants' self-ratings of self-esteem, control over food, and the degree they turned to food when stressed. User satisfaction data were collected with an online questionnaire. Latent growth modeling techniques were used to identify independent variables and possible mediating treatment process variables associated with weight change. Results: Mean age of participants was 16 years (range, 10-21), 65% girls, and 84% Caucasian. Twenty-seven (63%) completed the program. There was a significant decrease in %overBMI over time of 7.1. There were significant improvements in participant ratings of self-esteem, control over food, and a reduction in turning to food when stressed. Males, younger participants, and participants with higher levels of program compliance achieved better weight loss. Participants who reported that calling obesity an addiction made their guilt worse experienced poorer weight loss. Females were more likely than males to report "addiction guilt," and this partly mediated the overall gender effect. Conclusions: The staged, incremental food withdrawal approach was feasible to implement and was useful in helping reduce excessive weight, particularly among boys.