Taking regular exercise, drinking only in moderation and watching what you eat makes no difference to one's chances of reaching 100, research has found.
Those who are lucky enough to qualify for a telegram from the Queen have simply been dealt a good genetic hand at birth, the study indicates.
Academics studied almost 500 people between 95 and 109 and compared them with over 3,000 others born during the same period.
They found those who lived extremely long lives ate just as badly, drank and smoked just as much, took just as little exercise and were just as likely to be overweight as their long-gone friends.
The study was carried out by researchers at the Albert Einstein College of Medicine in New York, who interviewed 477 very long lived Ashkenazi Jews.
Prof Nir Barzilai, director of the college's Institute of Ageing Research, said previous studies of this group had identified certain genes which protected them from the effects of a normal Western lifestyle.
But critics argued the individuals themselves had lived healthier lives than others, and it was this that was more important for longevity.
This research, published today (Wednesday) in the Journal of the American Geriatric Society, indicates it really is the genes that matter.
"In previous studies of our centenarians, we've identified gene variants that exert particular physiology effects, such as causing significantly elevated levels of HDL or 'good' cholesterol," said Prof Barzilai.
He explained that this study provided evidence that these and other "longevity genes" helped "to buffer them against the harmful effects of an unhealthy lifestyle".
He said the first woman he interviewed, an 109-year-old, told him she had smoked 40 cigarettes a day for 90 years. While most people would have died of lung cancer or heart disease, she soldiered on.
Prof Barzilai emphasised that the research did not mean most people could live unhealthy lives and not expect to pay a price in the end.
He said: "Although this study demonstrates that centenarians can be obese, smoke and avoid exercise, those lifestyle habits are not good choices for most of us who do not have a family history of longevity.
"We should watch our weight, avoid smoking and be sure to exercise, since these activities have been shown to have great health benefits for the general population, including a longer lifespan."
He said he was horrified when, after a television appearance, a man addressed him in Starbucks and said he would never exercise again, because his grandmother had lived to 102.
When it came to the centenarians' views about why they had lived so long, the group identified good genes as the main reason, followed by diet and physical exercise.
Perhaps surprisingly, "God, religion or spirituality" did not get much credit, cited by only seven per cent of women and 2.5pc of men.