With chronic stress, the hypothalams directs the pituitary gland to signal the adrenal cortex to release a hormone called cortisol. According to research out of the University of New Mexico, elevated levels of cortisol can stimulate an increase in appetite and an increased rate in fat storage. If the stress is not controlled (real or perceived stress), the hypothalamus signals do not wind down and cortisol levels continue to increase.
Chronic stress is also associated with emotional changes (anxiety, depression and apathy) that often lead to overeating. If the emotions aren't controlled, negative patterns of eating are often observed.
The good news is that exercise can help protect against feelings of distress, reduce symptoms of anxiety, guard against depression and improve psychological well-being. Even short bouts of exercise can help! As to the intensity, moderate to vigorous physical activity has been recommended (Dunn and Jewell, 2010).