O'Connor points to a study that
...focused on Ashkenazi Jews, a group that is more genetically homogenous than other populations, making it easier to identify genetic differences that contribute to life span. In the study, the researchers followed 477 Ashkenazi centenarians who were 95 or older and living independently. They asked them about their habits and the ways they lived when they were younger. Using data collected in the 1970s, the researchers compared the long-lived group with another group of 3,000 people in the general population who were born around the same time but who generally did not make it to age 95...They found that the people who lived to 95 and beyond did not seem to exhibit healthier lifestyles than those who died younger.The article continues to discuss social, personality, and genetic factors influencing longevity. The take home message is that people with the genes for longevity live past age 95 with habits no different from most others, but the average person would probably have to follow a healthy lifestyle to live comfortably past 80.
And, here is a bit of sanity, from Gary Gutting, on trying to live forever. He emphasizes that correlations do not prove causes (lower HDL levels correlate with more heart attacks, but clinical studies show raising HDL (good) cholesterol with drugs does nothing to protect against heart attacks.) He argues against chasing after the latest dietary supplement whose relevance is implied from correlation studies ('It can't hurt, it might help'... which I'm guilty of), and simply following the humdrum standard advice we’ve heard all our lives about eating sensibly, exercising regularly, and having recommended medical tests and exams. Apart from that, "how we die is a crap-shoot, and, short of avoiding obvious risks such as smoking and poor diet, there’s little we can do to load the dice."