This article deals with the question of which longitudinal effect physical activity at the adult age can have on physical fitness and on people's subjective as well as objective state of health. Are persons who are regularly and continuously physically active healthier and fitter than people beginning physical activity at a later age, or than those who have never been physically active at all? The results of the presented longitudinal study, run over a time range of 10 years, with subjects at the middle and later adult age, show that on average physical fitness and subjective health decline with in the analysed time range, but positive effects of physical activity do exist. These show up in a decelerated decline. The constant sportsmen benefit most here, but also a late start with physical activity can improve and stabilize physical fitness and health. Anyway, former physical activity is no guarantee for lifelong fitness and health. The group of the dropouts registers large degradations in both variables after quitting physical activity.