One fundamental way how players relate to games is through the avatar they are represented by. In this work, we explore the impact of realtime adjustment of avatar appearance (visual body weight) on player motivation in exergames. Our results draw a mixed picture: while qualitative findings show that players were aware of adaptations, quantitative results do not demonstrate significant differences in player motivation. Instead, observations suggest that players leveraged the mechanic to develop their own meta-game, an effect that needs to be considered when designing mechanics that aim to improve player motivation in exergaming settings.