Here, with the help of leading clinicians, Angela Epstein identifies the ages when different parts of the body start to lose their battle with time.
There's no denying the ticking of a woman's biological clock - but men are not immune, either.
French doctors have found that the quality of sperm starts to deteriorate by 35, so that by the time a man is 45 a third of pregnancies end in miscarriage.
- Starts ageing at 40 The heart pumps blood less effectively around the body as we get older.
This is because blood vessels become less elastic, while arteries can harden or become blocked because of fatty deposits forming on the coronary arteries - caused by eating too much saturated fat.
It's then harder to work the lungs and also means some air remains in the lungs after breathing out - causing breathlessness.
Aged 30, the average man can inhale two pints of air in one breath. Starts ageing at 65Our voices become quieter and hoarser with age.Bladder capacity in an older adult generally is about half that of a younger person - about two cups in a 30-year-old and one cup in a 70-year-old.This causes more frequent trips to the loo, particularly as poor muscle tone means the bladder may not fully empty. Start ageing at 20 Lung capacity slowly starts to decrease from the age of 20.By the age of 40, some people are already experiencing breathlessness.This is partly because the muscles and the rib cage which control breathing stiffen up.More likely, says Gareth Evans, breast cancer specialist at St Mary's Hospital, Manchester, our cells become damaged with age - as a result, the genes which control cell growth can mutate, causing cancer.