Smokers and obese people cost healthcare systems less than healthy people, according to a new study from Holland reported in PLoS. But that headline doesn't tell the whole story writes Klim McPherson, Professor of Epidemiology at Oxford, in a companion article. The reason for the difference? Being obese shortens your life expectancy by around five years, while smoking reduces it by around seven years. Shorter lifespan = less total healthcare costs and reduced need for expensive care and treatment for ailments associated with old age. Professor McPherson comments: 'Certainly those who are obese and those who smoke will live fewer years on average, but will these people be compensated by enriched quality of their fewer years?' The research, he argues, doesn't shed any light on this quality of life issue as well as the cost dividend of improved health on other areas such as productivity at work, he adds: 'Translating individual costs and benefits to societal costs and benefits is never straightforward, and their study successfully emphasises the problem.'