The secret to long life may be a Mediterranean-style diet along with exercise and a little alcohol, according to a new study that’s likely to cause a gulp of uncertainty among Atkins-style dieters.

The study, one of the first to look at the individual and combined effects of diet and lifestyle in older people, found a 23 percent reduction in overall deaths during a 10-year period among those who adhered to a Mediterranean diet.

Similar reductions in deaths also were found among those who consumed moderate amounts of alcohol, primarily wine, at 22 percent lower; engaged in regular physical activity, 37 percent; and did not smoke, 35 percent.

Those who combined all four – diet, alcohol, exercise and not smoking – saw a 65 percent reduction in overall deaths, according to the study published Wednesday in the Journal of the American Medical Association.

Nearly the entire issue of JAMA was devoted to studies on the beneficial effects of diet and exercise, including one that found that walking two miles a day significantly reduced the risk of dementia in older men.

“These are just remarkable studies,” said Diana Kerwin, an assistant professor of medicine at the Medical College of Wisconsin. “This shows that at age 70, you can add some lifestyle habits and still impact your longevity.”

Several earlier studies have showed a connection between exercise and improved brain health later in life.

“I think diet and lifestyle play an important role in longevity. Even in old age, it matters if you consume a Mediterranean diet, consume moderate alcohol, are physically active and don’t smoke,” said Kim Knoops, lead author of the Mediterranean diet study and a researcher with the division of human nutrition at Wageningen University in the Netherlands.

The reductions came from lower rates of death from heart disease, cancer and other causes.

For the study, which followed 2,339 people aged 70 to 90 from 11 European countries for 10 years, a Mediterranean diet was defined as one that emphasized whole grains, fish, nuts, leugmes, olive oil, fruits, and vegetables and potatoes, but not meat and dairy products.

In the Atkins diet, now popular among many Americans, red meat typically is not restricted. Conversely, carbohydrates, including those that come from potatoes, many fruits, grains and alcohol, are cut dramatically.

“The Atkins diet focuses on weight loss,” Knoops said. “The aim of the Mediterranean diet is to maintain a stable weight.”

The problem with the Atkins diet is that even though people can lose weight on it, it’s difficult to stay on it for more than a year, said Eric Rimm, an associate professor of epidemiology and nutrition at the Harvard School of Public Health.

“For centuries, people have lived their lifetimes on the Mediterranean diet,” said Rimm, who co-authored an editorial in JAMA accompanying the study.

In an interview, Rimm said the popular South Beach diet probably comes the closest to a true Mediterranean diet, at least once people get past the initial weight loss phase.

His editorial noted that even though science may not fully understand how lifestyle affects health, enough is known to take action now.

“As a society, the United States spends billions on chronic disease treatments and interventions for risk factors,” the editorial said. “Although these are useful and important, a fraction of that investment to promote healthful lifestyles for primary prevention among individuals of all ages would yield greater benefit.”

A separate study followed 180 people with metabolic syndrome, an increasingly common condition in the United States. The syndrome, which affects nearly 50 million Americans, is defined as having any three of five risk factors for heart disease: excessive abdominal fat; high blood pressure; insulin resistance; high levels of triglycerides; and low levels of HDL cholesterol (the good kind).

Ninety of the patients were put on a Mediterranean diet, and after two years, only 40 still had metabolic syndrome, compared with 78 of the 90 people who were put on a low-fat diet.

Both groups increased their physical activity, but those on the Mediterranean diet lost more weight (8.8 pounds vs. 2.6 pounds). They also had substantially less inflammation in their blood stream; improved insulin resistance; and healthier blood vessels.

“The Mediterranean diet is rich in antioxidants, phytochemicals (healthy substances in plants) fiber and omega-3 fatty acids,” said senior author Dario Giugliano, a professor of metabolic diseases at the Second University of Naples in Italy.

In two other studies, walking was found to reduce the rate of dementia in older men and long-term physical activity, including walking, improved cognitive function in older women.

The walking study, which followed 2,257 men aged 71 to 93 for about six years as part of the Honolulu-Asia Aging Study, found that those who walked less than a quarter mile a day were 1.8 times more likely to develop dementia than those who walked more than two miles.

Physical activity may directly benefit the brain, and it may also improve brain health by improving cardiovascular health, said lead author Robert Abbott, a professor of biostatistics at the University of Virginia Health System.

“People who are physically active tend to have healthier lifestyles and better diet,” he added.