An increasing number of studies had showed that exercise prevented a wide variety of 'modern illnesses' - from heart disease to depression. What had not been firmly established was whether it was exercise taken in earlier life or current exercise which had been protective.

Then a 2000 study brought good news for couch potatoes - it's never too late to fight back. The 16-year study of 5209 men and women found no evidence that exercising earlier in life had protected against illness later, but huge protective benefit from present exercise (40% improvement overall).