Exercise

Free miracle cure! Reduce your risk of heart disease, stroke, diabetes and cancer by up to 50%! If there was a pill with these sort of success rates people would be queuing up to buy them. But why stand in a queue? Just walk around briskly and take some exercise and that's the sort of health benefits you can expect.

As a bonus it can also improve your sleep quality, give you more energy and reduce the risk of mental health diseases such as depression, dementia and Alzheimer’s.

And it doesn't have to be pumping iron down the gym. Regular movement is just a important - so if you commute, walk quickly to the train or bus and keep adding those minutes up throughout the day. Sedentary jobs and lifestyles are a big killer.

You need a balance of regular movement as well as muscle gain (resistance training) and aerobic exercise - plenty of walking is good but you also need a couple of sessions of vigorous (i.e. make you breath hard) exercise for the biggest benefits.

Notes:

recreational exercise is not associated with increased osteoarthritis - but high impact forces and twisting motions do
Thinning of shock-absorbing cartilage is a key feature of ageing but physical activity appears to reduce this thinning

It's Never Too Late To Start Exercising

Total mortality after changes in leisure time physical activity in 50 year old men - Byberg et al
Increased physical activity in middle age is eventually followed by a reduction in mortality to the same level as seen among men with constantly high physical activity.