Exercise is one of the top modifiable risk factors for chronic disease. Indeed, exercise produces roughly similar benefits to drugs in the secondary prevention of coronary heart disease, rehabilitation after stroke, treatment of heart failure, and prevention of diabetes. In addition, exercise has recently been shown to reduce the risk of dementia and improve mental health. The required dose is modest and achievable, with evidence suggesting that moderate intensity physical activity at even a minimum of 150 minutes a week is effective (about 30 minutes of physical activity most days comprising, for example, three 10 minute walks). And, with so much current attention on obesity, there is interesting evidence that, although both fatness and lack of fitness are associated with cardiovascular risk factors, maintaining or improving fitness may attenuate some of the adverse effects of fat gain with age.