Bright light therapy has been used to safely and effectively treat conditions such as Seasonal Affective Disorder and to regularize sleep in patients with circadian rhythm disorder. Based on evidence of the link between bright light, serotonin, mood and carbohydrate metabolism, it has been suggested that bright light therapy can improve weight loss but the literature on the subject is sparse. Further, the literature suggests that apart from any changes in mood and carbohydrate metabolism, bright light may reduce the unpleasant side-effects of exercise and increase compliance to an exercise program.