From a scientific standpoint, it seems that the key to living longer is eating less. Restricting calorie intake not only promotes weight loss, but recent experiments have shown that it also activates intracellular genes, which trigger longevity. When I heard about an organization in the United States putting this restrictive practice to use, I was curious. At the end of June, I made a trip to North Carolina to meet group member Bob Cavanaugh to learn more.
"Usually I don't eat lunch. Today is an exception because of the interview," said the 177-centimeter tall, 70-kilogram Cavanaugh, who operates a landscaping business in a town about two hours from the state capital, Raleigh.
Cavanaugh, 64, is also the managing director of the CR (Calorie Restriction) Society International. For the past 12 years, he has been limiting his caloric intake to about 70 percent of what the average, active adult male requires for a day.
Cavanaugh joined the society at the end of 2000 because of poor health. His cholesterol was high and when a doctor suggested he reconsider what he was eating, he got hold of a book about the relationship between longevity and calorie restriction.
Up until then he had been eating more than three meals a day, usually consuming a large steak at dinner and raiding the refrigerator throughout the night.
Now, breakfast consists of a bowl of oatmeal topped with sunflower seeds or something similar. He has nothing for lunch. Dinner is a salad, with legumes and chicken or salmon or tuna as a source of protein. He also drinks a single glass of red wine. As a general rule, bread and sugar are avoided.
Giving due consideration to nutritional balance, Cavanaugh aims for a daily intake of about 1,800 calories, the average among the society's members. In Japan, the rough intake target for adult males is between 2,000 and 2,400 calories. It is thought Americans consume about 30 percent more calories on average than the Japanese, so for Cavanaugh, whose work requires physical labor, his caloric intake is quite low. Among the society's members are some who only eat the equivalent of 1,000 calories a day.
Five months after embarking on his new dietary lifestyle, Cavanaugh's health improved, including lower cholesterol, and he was able to stop taking medications.
"When I was a child I had limitless energy. I feel like I've returned to that state. Life still moves forward like a conveyor belt, but I feel like its speed has slowed," he said.
In order to prevent osteoporosis, which has been indicated as a risk for those who limit caloric intake, Cavanaugh makes sure to get plenty of sunlight, walking five kilometers four or five times a week.
"Restricting caloric intake has proven to benefit longevity in experiments on animals, so I believe in it," he said.
The CR Society International, which was founded in the United States in 1994, currently comprises about 5,000 members worldwide, according to Cavanaugh.
In 1935, results from experiments with lab rats were already showing that limiting calories was extending their lives. These were followed with successful experiments on other living organisms such as flies and eelworms. And though restricted calories were shown to delay the aging process in rhesus monkeys, the mechanism enabling this outcome remained unknown.
Shedding light at the genetic level on this hitherto evasive mechanism has been a group of researchers led by Leonard Guarente, professor at the Massachusetts Institute of Technology, and Shin-ichiro Imai, associate professor at Washington University in St. Louis. In 2000, the group reported that when the gene sirtuin was activated in experiments involving yeast, the fungi's life span was extended, and that the same gene could be activated in mice. Their findings indicated that certain genes influenced longevity. Since then the group has also reported that limiting caloric intake activates the sirtuin gene. In short, restricting caloric intake activates the sirtuin gene, which in turn increases longevity.
"Activating sirtuin is like Clark Kent turning into Superman," Guarente explained.
Practical research along this line is moving forward. Guarente is developing a new drug to combat diabetes that activates sirtuin without the need to limit calories. Meanwhile, Imai is working to develop a new drug based on the hypothesis that life can be extended by activating sirtuin in brain cells. More than being cures for different diseases, the drugs aim to prevent internal organs from aging.
"By clarifying the aging and longevity mechanism, I want to make growing old in a healthy state possible. I believe this is necessary for Japan, where the population is rapidly aging," Imai said.
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