>that diet and exercise adjustment will fix hypertension in most (not all!) cases.

Not really although it can certainly help. There is evidence that there is a profound change (infection of some sort) in the Kidney and at some point that causes a run away inflammatory response that leads to Hypertension, it is an autoimmune condition that is extremely difficult to manage or get rid of. They believe it may be responsible for a great deal of Essential hypertension in adults today.