This dissertation explores conditions under which food messages backfire among consumers leading them to engage in behaviors that are opposite to what was intended by the messages. The first essay shows when and how food-related warnings can backfire by putting consumers in a state of reactance. Across three studies, I demonstrate that dieters (but not nondieters) who see a one-sided message focusing on the negative aspects of unhealthy food (vs. a one-sided positive or neutral message) increase their desire for and consumption of unhealthy foods. In contrast, dieters who see a two-sided message (focusing on both the negative and positive aspects of unhealthy food) are more likely to comply with the message, thereby choosing fewer unhealthy foods. My research suggests that negatively-worded food warnings (such as PSAs) are unlikely to work – nondieters ignore them, and dieters do the opposite. Although preliminary, the findings also suggest that two-sided messages may offer a better solution. The second essay shows how certain messages advocating for genetically modified organisms (GMOs) can backfire by activating consumers’ thoughts about risk of GMOs. Across four studies, I demonstrate that strong anti-GMO (but not weak anti-GMO) consumers who see a pro-GMO message claiming that GMOs are safe for human consumption (vs. a neutral message) perceive higher risk from GMOs, resulting in more unfavorable attitudes toward GMOs and lower intentions to consume GMOs. My research also suggests that a pro-GMO message claiming that GMOs are beneficial will be more effective in persuading both strong and weak anti-GMO consumers.