Have found daily exercise, something that makes me breath hard and gets my heart rate up, extraordinarily helpful. Have been a drunken, chain smoking couch potato for ~ a decade. Quit cigs, quit drinking, started exercising. Down below 200lb for the first time in some time. Feel better, look better (which makes me feel even better).
Don't know what is cause or what is effect, but still recommend giving exercise a serious try to all.