Walter Breuning, som 2009 ärvde den officiella titeln ”världens äldste man”, gick bort igår vid den aktningsvärda åldern av 114 år. Sitt långa liv tillskrev han sin vana att bara äta två mål mat om dagen, en regel han efterlevt i 35 år.
As the legions of lapsed dieters can attest, even modest calorie restriction can be hard to sustain. And not everyone who wants to be healthy and long-lived wants or needs to be stick thin.
Mark Mattson, a researcher at the National Institute on Aging in Baltimore, Maryland, thinks an alternate route may be through what he calls intermittent fasting. Health benefits in mice that eat only every other day are similar to those for mice that eat a calorie restricted diet—they live 30 percent longer, Mattson says. And, he adds, ”We see vast improvements in variables that indicate risk of disease.”
The calorie intake of the mice is not restricted—during the “on” days, they can eat as much as they like.
Indeed, Mattson’s findings suggest that one can enhance health parameters by regulating diet, even without losing weight. Intermittent fasting, like calorie restriction, may circumvent the aging process by reducing free radicals in the cells. Mattson explains that these highly reactive molecules can damage cells, and with age, the cells become less adept at eliminating them.
Although calorie restriction and intermittent fasting seem to induce similar health benefits, Mattson suspects the two approaches differ somewhat in their metabolic effects. Based on his cellular studies, he says, “Fasting seems to increase the resistance of cells to various types of stress that can cause disease, while calorie restriction may be more effective at curtailing free radicals.”
The idea is counterintuitive: If we eat to live, how can starving ourselves add years to our lives? Yet decades of calorie-restriction studies involving organisms ranging from microscopic yeast to rats have shown just that, extending the life spans of the semistarved as much as 50%. Last July a long-term study led by researchers at the University of Wisconsin nudged the implications of this a bit closer to our species, finding that calorie restriction seemed to extend the lives of humanlike rhesus monkeys as well. The hungry primates fell victim to diabetes, heart and brain disease and cancer much less frequently than their well-fed counterparts did.
Scientists have suspected that calorie restriction could extend the life span of animals since at least 1935, when researchers at Cornell University noticed that severely food-restricted lab rats lived twice as long as normal ones and were healthier. Other investigators began exploring the idea and learned that the secret is not merely a matter of body weight: lab mice that ate normally but became skinny by exercising a lot showed no longevity improvements. Only the ones that didn’t get many calories to begin with benefited.
One theory is that a state of slight hunger acts as a mild but constant stressor that makes an organism stronger and more resistant to the ills of aging. Taking in fewer calories also slows metabolism, and some data indicate that humans with a slower metabolism live longer.
On a recent morning, Cavanaugh, who lives in coastal North Carolina, prepared his breakfast, the same one he has had most days since starting the calorie-restrictive diet eight years ago: a quarter cup each of oatmeal, oat bran, powdered skim milk, and liquid skim milk. After two minutes in the microwave, he topped the concoction with half a cup of frozen blueberries—to provide antioxidants and improve mental crispness—and two tablespoons of sunflower seeds that will fulfill 60 percent of his daily vitamin E requirements. He washes down his 451-calorie breakfast with a cup of coffee. He won’t eat again until dinner and claims he won’t be hungry until then.
”My breakfast gives me more than half my nutrition for the day,” says Cavanaugh, who’s pre–calorie restrictive eating habits included bacon and eggs, hot dogs, chips, and cinnamon buns. ”It’s so filling, I just don’t get hungry for lunch.”
Five months into his new lifestyle, Cavanaugh’s cholesterol dropped 103 points, and his triglycerides dropped from 145 to 63 (a healthy number is 150 or below). Now 140 pounds, he claims he hasn’t had a cold in eight years, and the chronic athlete’s foot and jungle rot he suffered since his time in the Marines has disappeared completely. His energy levels have skyrocketed. ”Remember when you were a kid and you would suddenly just take off running across the yard because of the exhilaration of energy? That exhilaration came back to me,” Cavanaugh says. ”I haven’t felt like this since I was a teenager playing tackle football.”