Sleep allows an overactive adrenal to rest overnight, also allowing your melatonin to give you a good night's sleep. Cortisol and melatonin are agonists, and fight for dominance. Cortisol is a stress hormone made by the adrenal gland and melatonin is an antioxidant sleep hormone produced by the pineal gland at night, in darkness. Normally melatonin takes over the night, slowing down cortisol production in the adrenal gland and encouraging proper rest and repair cycles. Then it wanes and cortisol and other adrenal hormones take over during the day, giving you energy. They should switch off in a normal daily cycle. If the adrenal won't shut down properly overnight due to stress, one may have inadequate melatonin resulting in an improper rest and repair cycle wearing you down. High cortisol levels are also associated with encouraging the depositing of fat in the abdomen, specifically. So reducing cortisol may also inhibit the formation of abdominal fat.