Many researchers in the literature participated in solving the obesity epidemic that has spread worryingly nowadays. One of these solutions is the mobile serious games. In this paper, we designed, developed and deployed a mobile serious game entitled StarsRace. It is a collaborative game, which two players involve in one match. This competition depends on rapid arrival to pre-defined geographical points (representing by stars images) on the map. Players collect stars form these locations and gain points. The therapist with respect to the players' profiles distributed those stars. To make the game more fun, we have added an aid toolbox that can increase the competition. Lastly, we evaluate our game using an evaluating model proposed by Nokia Research Center. We find that our game cover nearly all the model criteria.