How quickly one heart beat returns to normal after strenuous exercise, to me - is the measure of health and fitness.
Fitness is subjective. It depends what you do or are training for. Powerlifters are fit for powerlifting whilst a marathon runner isn't and vice versa.
Health is also very hard to pin down. The blood work markers are a good basic starting point but there is so much more and so many genetic differences that changes everything when using goals like we do now.