The Grapefruit Diet is a common fad diet that promises dramatic results and is only popular for a short period of time.
Maybe when an organism has both an endocrine and a nervous system it is able to not only make rapid changes to be more well-adjusted in its enviroment but is also able to make changes required for survival in long-term.
When you are exercising, you're blood pressure is elevated. When you are finished exercising, it will recede to near it's normal state. Exercise doesn't have as much of an affect as weight does, but I guess all these things are all kind of inter-related. The more physically fit you are, the lower your blood pressure, in general.
