Researchers from University College London followed 3,454 people over eight years. At the start of the study, all the participants were healthy and had an average age of 64. Those who had exercised regularly at least once a week at the start of the study were three to four times more likely to be classified as a "healthy ager"—free of chronic disease, physical or cognitive decline and depression—than inactive participants at the end of the study.

The biggest positive effects of exercise were seen in the people who exercised the longest—those who were active throughout the whole 8-year period were seven times more likely than inactive people to be healthy at the end of the study. More surprisingly, even people who only began to exercise after the start of the study—after a lifetime of inactivity—were still three times more likely to be healthy 8 years later. Notably, the people who were active were not just less likely to develop a physical disease, they were also mentally sharper and less likely to be depressed.

From What Doctors Don't Tell You via the British Journal of Sports Medicine, 2013; doi: 10.1136/bjsports-2013-092993.

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