Fashionable diets come and go all the time, but now researchers say they have finally been able to find one that has everything it takes to live a healthy, long life. The "longevity diet" consists of fish and plant proteins, and even surprisingly includes carbohydrates, while avoiding red and processed meats.

So what’s different? This diet requires people to eat their meals within a certain time frame and allow time for periods of fasting. For those who want to stick to a healthy diet there’s many options, with most programs focusing on reducing carbohydrate and calorie intake. Yet it’s unclear if these diets help people stay healthy and live longer.

Now, a team from the University of Southern California whose research is published in the journal Cell has found that it has to do not only with what people eat, but also with when they eat.

"We have studied the relationship between nutrients, fasting, genes and longevity, and linked these connections to clinical and epidemiological studies in primates and humans including centenarians," Professor Valter Longo said in a statement on the university's website.

 A combination of the best dietsResearchers reviewed hundreds of studies on nutrition, disease and longevity, which included both animals and humans, and combined results with their own research. They analyzed a wide range of low-calorie diets like the popular keto diet, as well as vegetarian, vegan and Mediterranean diets. The study also examined various forms of fasting, sometimes for two days or more and also several times a month.
Ketogenic diets are high in fat from foods such as avocado. (credit: MAXPIXEL)
Ketogenic diets are high in fat from foods such as avocado. (credit: MAXPIXEL)
The team found factors associated with longer life and certain diseases such as insulin, cholesterol and certain protein levels. The authors of the study believe that the secret to a longer life is to eat a moderate to high amount of carbohydrates from unprocessed sources. Also, getting the right amount of protein and enough fats from plant sources can provide about 30% of a person's energy needs.

Ideally, meals should take place within a window of 11 or 12 hours, allowing for a time of fasting that maintains balanced insulin levels and blood pressure, the study finds.

What’s in a longevity diet?

"Lots of legumes, whole grains and vegetables, little fish, no red meat or processed meat at all, and a very low amount of pork, a low-sugar diet and processed grains, good levels of nuts and olive oil, and some dark chocolate," says Longo.

Their new menu is reminiscent of Mediterranean diets, which are found in so-called "blue islands"  (places with numerous centenarians) like Sardinia in Italy, Okinawa in Japan, and even here in Israel. These diets are usually plant-based with some seafood and relatively low in protein.

The longevity diet adds to this by also providing time frames for meals and fasting periods that people can adjust to suit their gender, age, health status and genetics. For example, people over age 65 need more protein to cope with body mass loss. Next, researchers plan to conduct a study of 500 people who will try the longevity diet in southern Italy.

"The longevity diet isn;t a dietary restriction designed only to cause weight loss, but a lifestyle focused on slowing down aging, which can supplement standard health services, and through prevention will help prevent morbidity and maintain health until old age," Longo concludes.