Message framing (i.e., emphasis on gains or losses) is a communication strategy that has been used to promote physical activity (PA). Previous research has led to inconsistent results regarding the persuasive effect of gains and losses. The purpose of this dissertation was to explore whether a fit between message content and individuals’ motivational orientation improves the effectiveness of messages. Undergraduate students participated in studies via the Department of Psychology SONA system. Study 1 (n = 441) tested whether a fit between Frame (gains, losses), Regulatory Focus (promoters, preventers), and Message Valence (positive, negative, mixed) improves the persuasiveness of PA messages. Study 2 (n = 449) explored the effect of gains / losses by using different probability sizes.

Study 1 revealed a three-way interaction on attitude, F(2, 428) = 5.25, p = .006, partial η2 = .024. Gains / losses worked better for promoters / preventers, respectively, when exposed to mixed content. Study 2 disclosed a main effect for Frame, F(1, 436) = 6.57, p = .011, partial η2 = .015, with losses being more effective on vigorous-intensity PA (VPA) intention; a main effect for Magnitude on moderate-intensity PA intention scores, F(2, 436) = 4.27, p = .015, partial η2 = .019, with an emphasis on 10 vs. 15% being more persuasive, followed by 5 vs. 10%, and 15 vs. 20%; and a Focus x Magnitude x Frame interaction on VPA intention, F(2, 436) = 4.13, p = .017, partial η2 = .019, with losses being more effective for promoters when exposed to small (5 vs. 10%) and big probabilities (15 vs. 20%), and more effective for preventers when exposed to medium (10 vs. 15%) and big probabilities (15 vs. 20%). These results indicate that customized messages can improve the effectiveness of mass media campaigns that disseminate the PA guidelines, which in turn can improve other sectors of the National Physical Activity Plan (e.g., Healthcare, etc.).