Roizen used the same principles that he says have kept him young to develop a wellness institute at the Cleveland Clinic, giving employees financial incentives to implement healthy lifestyle changes. Since 2008, the program has saved Cleveland Clinic up to $200 million a year on healthcare costs for 101,000 employee patients since 2008, Roizen said. It’s also helped inform the clinic’s research initiatives on healthy aging.

Here are the diet principles Roizen follows.

Eat a Mediterranean diet

The Mediterranean diet primarily consists of whole foods such as fruits and vegetables, legumes, low-fat protein and dairy, and limits red meat, processed foods, and alcohol. It’s been named the healthiest diet for seven years in a row by US News & World Report, and research has linked it to better heart health, weight loss, and less cognitive decline.

Trout and salmon, which are packed with vitamin D and omega-3 fatty acids, are Rozien’s major sources of animal protein.

Eat a big meal at lunch

Roizen has his biggest meal at lunch and eats “very little” at dinner — usually just a salad. He can’t sleep well after a heavy meal and feels “much worse the next day,” he said.

A study released this year by researchers at the University of Alagoas in Brazil found that eating most of your calories at lunch could help to prevent and treat obesity, regardless of the quality of a participant’s diet. Eating this way may align better with the body’s natural rhythms, the team suggested.

Restrict calories 5 days a month

Roizen also follows the Longevity Diet, developed by Valter Longo, a professor of gerontology and the director of the University of Southern California Longevity Institute. Rozien said he’s been following the diet, which involves restricting calories five days a month to mimic the effects of fasting, for seven years.

A study released this year by Longo’s team at USC found that participants on the fasting-mimicking diet had lower biological ages by an average of 2 ½ years after three months on the diet. Participants consumed about 1,100 calories on the first day of the diet and then about 700 calories on days two to five.

David Clancy, who ​​studies the biology of aging at Lancaster University in the UK but wasn’t involved in the study, told BI at the time: “It’s not unreasonable to think that during ages 40 to 60 at least, this regime twice per year may add three to four years of healthy life, maybe more, in those with higher BMI, blood pressure, blood sugar, etc.”

But Clancy acknowledged that the diet was “harsh” and that working people may struggle to follow it. “Scheduling days four and five for weekend days would be sensible,” he said.

Eat in an 8-hour window

Roizen fasts intermittently by eating between 11 a.m. and 7 p.m. each day.

He said that while the data on the impact of intermittent fasting on longevity is not as solid as the data on calorie-restricted fasting, he likes how he feels when he follows that schedule.

“By the end of that 16-hour period, I’m feeling great and very energetic. I sleep much better and I seem to have much more energy as well,” he said.

BI previously reported that research on the potential benefits of intermittent fasting isn’t conclusive. One controversial study released earlier this year suggested that it may actually shorten a person’s lifespan, and others have suggested that it doesn’t provide any health benefits.