The beneficial effects of exercise have been well recognized for over half a century. Dr Jeremy Morris's pioneering studies in the fifties showed a striking difference in cardiovascular disease between the drivers and conductors on the double‐decker buses in London. These studies sparked off a vast amount of research on the effects of exercise in health, and the general consensus is that exercise contributes to improved outcomes and treatment for several diseases including osteoporosis, diabetes, depression and atherosclerosis. Evidence of the beneficial effects of exercise is reviewed here. One way of highlighting the impact of exercise on disease is to consider it from the perspective of good practice. However, the intensity, duration, frequency (dosage) and counter indications of the exercise should be taken into consideration to individually tailor the exercise programme. An important case of the beneficial effect of exercise is that of ageing. Ageing is characterized by a loss of homeostatic mechanisms, on many occasions leading to the development of frailty, and hence frailty is one of the major geriatric syndromes and exercise is very useful to mitigate, or at least delay, it. Since exercise is so effective in reducing frailty, we would like to propose that exercise be considered as a supplement to other treatments. People all over the world have been taking nutritional supplements in the hopes of improving their health. We would like to think of exercise as a physiological supplement not only for treating diseases, but also for improving healthy ageing.