Advair Diskus, Weight Gain

My son, 8 year old takes Advair for his asthma and has been gaining weight and looking doughy for the past several months. He is very active and plays basketball, bike rides and plays high energy sports every day and I can't believe the way he looks. Has anyone else experienced this themselves or with their children? What can I do to change from this medication to something that won't have this effect?