Infection with obesifying adenoviruses in animals and humans may be used to predict changes in body weight and disease status. More particularly, infection with certain adenoviruses, such as adenovirus type 36 (Ad-36) and adenovirus type 37 (Ad-37) may cause removal of the normal equilibrium factors that control fat cell metabolism and may make individuals more responsive than normal individuals to perturbations, which cause body composition change including weight gain or weight loss.