Cholesterol-lowering drugs are widely prescribed to reduce LDL - low-density lipoproteins, the so-called ‘bad’ cholesterol - believed to be implicated in heart disease. However, exercise has been found to do the same job as the drugs - and more besides. Exercise not only significantly reduces LDL, but also increases levels of HDL - high-density lipoproteins - the ‘good’ cholesterol that prevents atherosclerosis.

How much exercise is necessary? Fairly brisk walking over 12 miles a week will lower LDL, but only sustained moderate exercise, such as jogging 20 miles a week, will raise HDL. Researchers say that it’s not so much the intensity as the amount of exercise that counts (N Engl J Med, 2002; 347: 1483-92).

* Exercise is equally good news for those who suffer from osteoporosis, where even a moderate amount of activity is of benefit. Just walking for one hour four times a week will halve the risk of hip fracture in postmenopausal women - but not if they’re taking HRT (JAMA, 2002; 288: 2300-6).