Exercise and health: the evidence

• Exercise can extend your life. The more energy a man expends each week in vigorous physical activity (such as brisk walking, jogging or running), the less likely he is to die prematurely from any cause, according to a long-term study of over 17,300 men in the USA.
• A study of almost 10,000 men aged 20–82 found that men who changed from being unfit to fit between two health examinations about five years apart reduced their risk of dying by 44% compared with those men who remained unfit throughout.
• Exercise is particularly good for the heart. A study of over 7,700 middle-aged British men showed that inactive men are not only more likely than active men to suffer a heart attack, they're also about twice as likely to die from it.
• There's very strong evidence that physically active men are much less likely to develop colon cancer than sedentary men. One large US study found that active men run about half the risk.
• Exercise is good for your bones. A study of over 5,000 retired men in California found that those who exercised for less than 30 minutes a day ran twice the risk of a hip fracture compared with those exercising for one hour or more.
• Physical activity helps prevent diabetes. A 14-year study of almost 6,000 University of Pennsylvania graduates found that the incidence of diabetes declined by 6% for each additional 500 calories burnt off each week during physical activity.
• However, it's also worth remembering that there's a fine line between super fitness and ill-health. There is evidence, for example, that regular intensive training can weaken the immune system.