This study examined how avatar body size (normal, obese) and opponent character body size (normal, obese) influenced physical activity while male participants played an exergame. Males operating normal weight avatars showed more physical activity than those using obese avatars. Perceived avatar and opponent character body‐size differences moderated the effect of avatar appearance on physical activity. Participants showed decreased physical activity when the opponent character was perceived as slightly more obese than their avatar. Participants also showed decreased physical activity when their avatar was perceived as more obese than the opponent character. We discuss theoretical implications and applications of using virtual characters to increase gamers' physical activity. These findings are also compared to an earlier study with an all‐female sample.