Obesity is also somewhat of a "self-fulfilling prophecy"
I know for me at least, I suffer frm clinical Depression. Some days it is all can do to get out of bed in the morning.
Intellectually I KNOW that exercise and staying away from the carbs and sugar will make me feel better in the long run. But when I am looking down that deep, dark hole of depression; situps don't make me feel better- they make me feel fatter. However i can easily zoneout while eating a Milky Way.