Background: Motivating Adolescents with Technology to CHOOSE Health™ (MATCH) is an educational and behavioral intervention in seventh grade. Methods: Teachers in 2 schools delivered the MATCH curriculum, with 1 control school. Using a quasi-experimental design, outcome measures included lessons completed, body mass index (BMI), BMI z-score (zBMI), BMI percentile, weight category, and self-reported lifestyle behaviors. We used multiple regression models to compare group results. Results: For the MATCH group (N?=?189), teachers provided lessons over 14 weeks; the control group (N?=?173) received usual curriculum. Postintervention, the MATCH group had significant decreases in BMI measures compared with the control. In combined overweight and obese participants, the mean (95% confidence interval) zBMI change was -0.05 (-0.07, -0.03) in MATCH and -0.01 (-0.04, 0.02) in control, p?=?0.034 between groups. After 1 year, improvements are sustained: for the overweight subgroup, the mean zBMI decreased from 1.34 to 1.26 post-MATCH, then to 1.26 after 1 year; for the obese subgroup, mean zBMI?=?2.16, to 2.13 post-MATCH to 2.08 after 1 year. Self-reported lifestyle behaviors showed no differences. Conclusions: MATCH integrates theory-based strategies into standard curriculum delivered by teachers. No prior middle-school intervention has shown sustained change in BMI measures. MATCH warrants further study as a strategy to address obesity.