Aerobic exercise, such as jogging, improves oxygen consumption, which in turn improves the body's ability to help in converting fat into fuel for muscles. The volume of oxygen people are able to consume is reduced with age, and therefore to maintain good health and the appearance of youth, more aerobic exercise is required, according to the researchers.

The study, led by University of Toronto scientists, found that high-intensity exercise, taken regularly for more than a year, can make someone as fit as a sedentary person who is 12 years younger.

"There seems good evidence that the conservation of maximal oxygen intake increases the likelihood that a healthy elderly person will retain functional independence," one of the study's authors was quoted by the British media as saying. Previous studies have suggested that maximum aerobic power falls in men by up to half between the ages of 20 and 60. Women begin to lose aerobic power aged around 35, with aerobic power again falling by up to half by the age of 60.