Previous research has shown that being observed can influence people’s behaviors, including their eating habits. In this study, we predicted that men and women would exhibit different reactions to the perception of portion size of meat when being observed. By utilizing a camera to create a sense of being observed during the act of eating meat, we revealed that men in the observed condition reported perceiving the portion size of the meat they ate to be smaller and the eating amount to be less than was reported by those in the non-observed condition. However, women did not show any differences in their perceptions of the portion size of the meat they ate. These findings demonstrate that gender identity plays a role in how people perceive the meat they eat when they are aware of being observed. The discussion highlights the effect of being observed on meat consumption and illustrates the influence of masculine identity.