We all have a fond but bittersweet memory of That One Guy who lived about as healthy a life as he could, prided himself on his diet and exercise regimen, yet still died too young. Sometimes we may even use him as justification to not eat well or exercise properly. After all, if it didn't work for that one friend the health nut, why should we even bother?

It is likely that your friend's biological age was considerably older than his calendar age. As scientists are just now coming to understand, our true biological age – and so, how soon we die – is driven by DNA factors that don't always jive with our “true” age.

Science is now trying to crack that DNA clock code, and there is hope that when we do, we may even be able to control our aging.

“Our research reveals valuable clues into what causes human aging, marking a first step toward developing targeted methods to slow the process,” says UCLA geneticist Steve Horvath, a professor of human genetics and biostatistics at UCLA’s David Geffen School of Medicine and Fielding School of Public Health. He is leading a team of 65 scientists in seven countries to record age-related changes to human DNA, calculate biological age and estimate a person’s lifespan. Their research is published in the journal Aging.

The team examined 13 sets of data, including the Framingham Heart Study and Women’s Health Initiative. They applied a mix of molecular methods that included an epigenetic clock to measure the aging rates of each individual. The clock calculates the aging of blood and other tissues by tracking methylation, a natural process that chemically alters DNA over time.

“We were stunned to see that the epigenetic clock was able to predict the lifespans of Caucasians, Hispanics and African-Americans,” said first author Brian Chen, a postdoctoral fellow at the National Institute on Aging. “This rang true even after adjusting for traditional risk factors like age, gender, smoking, body-mass index, disease history and blood cell counts.”

So is this all good news, science is beginning to get a handle on aging, we'll all start living longer?

Not exactly.

The scientists discovered that 5 percent of the population ages at a faster biological rate – with a commensurately shorter lifespan.

“While a healthful lifestyle may help extend life expectancy, our innate aging process prevents us from cheating death forever,” Horvath drove home the bad news. “Yet risk factors like smoking, diabetes and high blood pressure still predict mortality more strongly than one’s epigenetic aging rate.”