As obesity rates rise, new weight-loss methods are needed. Little is known about the use of podcasting (audio files for a portable music player or computer) to promote weight loss, despite its growing popularity.A 12-week RCT was conducted.The study sample comprised overweight men and women (BMI=25–40 kg/m 2 ; n=78) in the Raleigh–Durham NC area.In 2008, participants were randomly assigned to receive 24 episodes of a currently available weight-loss podcast (control podcast) or a weight-loss podcast based on social cognitive theory (SCT) designed by the researchers (enhanced podcast) for 12 weeks.Weight was measured on a digital scale at baseline and follow-up. Both groups also completed questionnaires assessing demographic information, food intake, physical activity, and SCT constructs at the introductory and 12-week meetings. Additional questionnaires at the 12-week meeting assessed perceptions of the intervention.Data collection and analysis occurred in 2008 and intention-to-treat was used. Enhanced group participants (n=41) had a greater decrease in weight (−2.9±3.5 kg enhanced group vs −0.3±2.1 control group; p<0.001 between groups) and BMI (−1.0±1.2 kg/m 2 enhanced group vs −0.1±0.7 kg/m 2 control group; p<0.001 between groups) than the control group (n=37) and had greater weight-loss–related knowledge (p<0.05), elaboration (p<0.001), and user control (p<0.001) and less cognitive load (p<0.001).The results of this study suggest that the use of behavioral, theory-based podcasting may be an effective way to promote weight loss.NCT00771095