People who continue to smoke despite the obvious health risks have been given another reason to quit as research shows it decreases muscle mass in old age.
Smoking is already known to cause cancer, strokes, and heart attacks, but it is now believed to make people lose muscle tissue as they get older.
The University of Nottingham study, which is published online in the American Journal of Physiology, compared 16 men and women - both smokers with a long-standing 20-a-day habit and nonsmokers - in their mid-60s.
Earlier studies have found smokers tend to have a lower muscle mass than those without the habit, but until now no-one has understood why.
But Prof Michael Rennie and Dr Philip Atherton, with colleagues in Denmark and the United States, have found that smoking raises the risk of sarcopenia, which is linked to increased falls and bone fractures.
Dr Atherton said: "From our tests, we can conclude that smoking slows the muscle protein synthesis machinery - probably impairing day-to-day upkeep of muscle.
"We are all well aware of the ill affects of smoking on the lungs, but our study reveals yet another cause of ill-health associated with smoking.
"Hopefully the UK smoking ban will encourage people to quit while they are still young, helping them to keep in good health in later life."