Introduction: The goal of the present study is to test whether social norms, given their power to justify behaviors, can protect the subjective well-being of group members when they engage in unhealthy eating. Method: A three-wave longitudinal study (before T1, during T2, and after the Christmas holidays T3) was conducted (N = 318). Results: Results demonstrated that changes in pro-unhealthy eating norms play a moderating role in the relationship between changes in unhealthy eating and changes in subjective well-being from T1 to T2, but not from T2 to T3. Specifically, when unhealthy eating increased from T1 to T2, a parallel increase in the strength of social norms buffered against a decrease in group members' subjective well-being. The absence of moderation between T2 and T3 could be due to the fact that pro-unhealthy eating norms became less salient at T3. Discussion: These results confirm that when unhealthy eating is salient in a social context, social norms can buffer against its negative impacts. Highlights and Implications * During the Christmas holidays period, individuals eat more unhealthy food and perceive that groups to which they belong eat more unhealthy food and encourage more consumption of this type of food compared to approximately 1 month and after the Holiday period. * When individuals perceive that groups to which they belong encourage more unhealthy food consumption from 1 month before to the Christmas holidays period (i.e., a social context where junk food consumption is salient and socially acceptable), their subjective well-being suffers less as a result of more unhealthy food consumption during this time period. * When individuals increase unhealthy food consumption from the Christmas holidays to 1 month after, they still experience an overall decrease in subjective well-being over the same time frame. * Overall, the social context in which eating takes place plays a vital role in shaping individuals' eating behaviors and the relationship of eating behaviors to well-being.