Johns Hopkins neurology professor Ted Dawson’s cholesterol was creeping into dangerous territory when his doctor recommended statins. Dawson decided to try intermittent fasting first, a restrictive eating schedule that mimics the feast-then-famine life of prehistoric hunters.

“Sure enough, it lowered my cholesterol,” Dawson says. “I never needed a statin.”

That was about 10 years ago. Dawson, now 60, still follows the regimen, consuming just 500 calories a day, twice a week. “To be honest, it’s still a pain,” he says. But his cholesterol levels keep improving, and his energy levels are high, he says.

On his low-calorie days, Dawson eats a little oatmeal or yogurt in the morning, a handful of nuts and fruit mid-day, and a veggie burger with no bun for dinner.

On the remaining days, he eats whatever he wants — in generous quantities. “My caloric intake is probably what it was when I was 25 or 30,” says Dawson, who now has to work to keep his weight up. “For health reasons, I try to stick to a Mediterranean diet, but I like ice cream and other desserts, so I’ll eat those too. I have red meat once in a while.”

A growing body of research, much of it led by Mark Mattson, adjunct professor of neuroscience, indicates the regimen offers a host of benefits, such as helping adherents shed pounds, lower blood pressure and cholesterol, slow the progression of Parkinson’s and Alzheimer’s diseases and reduce cancer risk.

In December, Mattson and Rafael de Cabo of the National Institute on Aging put much of that information in one place, publishing a widely publicized research review in the New England Journal of Medicine.

The catalyst for intermittent fasting’s health benefits, they say, is metabolic switching, which occurs when cells transition from using glucose for energy to using ketone bodies, and then back again.

A typical carbohydrate-rich diet of three meals a day plus snacks provides more than enough glucose to power cells. But during fasting, glucose runs out and the liver responds by converting fatty acids to ketone bodies, a process known as ketosis. Ketone bodies provide steady, fat-derived energy and appear to regulate proteins and molecules related to health and aging, they write.

Mattson focuses on two specific regimes: the two-days-a-week fasting schedule practiced by Dawson; and the time-restricted schedule practiced by Mattson, which requires consuming the day’s food in a window of six to eight hours and fasting the rest of the time. Studies have not yet compared the relative efficacy of the two regimens, says Mattson.

Both eating plans advocate a healthful diet, but don’t include instructions about what foods to eat or how many calories to consume. “If someone’s normal diet is unhealthy and they switch to intermittent fasting it will probably benefit their health,” says Mattson. “If they’re already eating a healthy diet, the intermittent fasting will turbocharge it.”

Mattson began shortening the time frame in which he eats in 1982, he said, when he gave up breakfast because it upset his stomach before bicycling to his graduate school campus. He now consumes his day’s calories between 1 and 7 p.m., eating mostly vegetables, fruits, nuts, whole grains, beans and yogurt.

He began studying intermittent fasting in the 1990s as part of his research into Alzheimer’s and other neurodegenerative diseases. “We knew every-other-day fasting had an anti-aging effect on rats in the sense that it increased lifespan, so we asked if this change in eating pattern would protect nerve cells and keep them functioning better longer,” he says. “We found that it did.”

Research on the potential benefits of intermittent fasting is still in its early stages. One challenge is getting study participants to stick with the restrictive eating plans. In their paper, Mattson and de Cabo recommend starting slowly, by restricting eating just one day a week or eating in a 10-hour window.

Dawson agrees that the regimen requires discipline, especially in the first few weeks. He makes it even more challenging by putting his two low-calorie days next to each other, usually Sunday–Monday or Monday–Tuesday. “What you’re trying to do is push your body to a ketotic state,” he says. “If you do it a second day, then the entire second day you’re in a ketotic state, and I think you get more benefit.”

The low-calorie days can trigger migraines, he says, but he’s usually able to prevent them by drinking a lot of water. By the end of the second day, he says, he is ravenous. “My brain is telling me it needs energy,” he says.

“But I’m still able to work at a pretty high level. I feel a little more sharp, a little crisper. It’s probably whatever the ketotic state has induced my body to release.”