Five behaviors could extend life expectancy at 50 by more than a decade, even without the discovery of a single new drug or medical treatment.

Researchers analyzed two large databases with 34 years of detailed health and lifestyle information on more than 123,000 men and women. Over the years, there were 42,167 deaths.

The study, in Circulation, looked at five behaviors: eating a healthy diet, not smoking, getting regular physical activity, moderate alcohol consumption and maintaining a normal weight.

The scientists calculated that, on average, a 50-year-old man who adopted all of these would live 12 years longer than a man who took on none. A woman with the same five habits would live an average of 14 more years than a woman with none of them.

The more low-risk factors a person had, the longer his or her projected life span. For example, a 50-year-old woman with four healthy factors could expect to live, on average, to around 89, those with three to 87, and those with two to 84.

Unfortunately, less than 2 percent of the people studied had all five low-risk factors, and a third had two or fewer.

“The question is how to improve behavior,” said the senior author, Dr. Frank B. Hu, a professor of medicine at Harvard. “Individual changes are not sufficient. We need dramatic changes in food, physical activity and social environment to make healthy choices more accessible, affordable and normative.”