A great question 300 and you have opened a can of worms!!!
For decades doctors have told overweight couch potato middle aged men with high blood pressure to eat healthily, cut down salt, stop smoking and drinking, and exercise. All good general advice BUT no hard evidence exercise itself did anything unless it helped to lose weight.....
However there have been a number of studies over the past 5 years looking at exercise. We know exercise reduces the risk of diabetes, reverses early diabetes, corrects abnormal lipid profiles (high fat levels in the blood) and reduces the risk of cardiovascular events (heart attacks and strokes). Weaker evidence suggests regular exercise reduces the future risk of high blood pressure. And as part of a regimen including diet / smoking / etc reduces blood pressure.
However regardless of the level of the evidence regular exercise, until a few years ago seen as a fad by most doctors, clearly reduces future risks. It even reduces the risk of death from cancer, but that is another story.........