"The point is, nutrient density, not calories, in food, is key. "
Maybe gene manipulation will allow us to live to 200—someday. Until then, there’s calorie restriction (CR). Three large studies are under way to test the principle in people. Early findings show promise. In 2007, researchers at Washington University in St. Louis reported that CR improved heart function and lowered inflammation levels in a group of volunteers—two signs that could mean better health and longer life down the road. In a study of 48 volunteers, Eric Ravussin and his colleagues at Louisiana State University’s Pennington Biomedical Research Laboratory found that after six months those men and women who cut calories by 25 percent reduced their insulin levels and their core body temperature—two changes associated with longevity. They also had fewer signs of the kind of chromosomal damage that is associated with aging and cancer.
Clinical trials are far from proving that CR dramatically extends life span in humans. Still, an estimated 50,000 Americans subscribe to CR, a practice popularized by Roy Walford, M.D. Walford, a pathologist at UCLA, wrote several books—including Beyond the 120-Year Diet—on the health benefits of eating a low-calorie, high-nutrient diet. (Walford died in 2004, at age 79, from complications of Lou Gehrig’s disease.)
Peter Voss, 53, is an expert in artificial intelligence who runs a start-up firm in Los Angeles. A Google search led me to Voss’s lively website about his experiences with CR (optimal.org), which he began in 1997. He now consumes just 1,850 calories daily, which he guesses is about one-third less than what he ate more than a decade ago. “The more I read about calorie restriction, the more interested I became, until I finally decided to give it a try,” he told me when I reached him. Five foot 10 inches tall, he now weighs 130, down from 155 pounds 10 years ago. His blood pressure, good to begin with, resembles that of an active teenager, about 100/60. His triglyceride and cholesterol levels are rock bottom.
In the beginning Voss scrupulously counted calories and scoured nutrient labels. Now he monitors his progress by keeping his weight stable. Voss’s diet is Spartan by any standard. Steel-cut oatmeal with fruit and skim milk is a special treat. But Voss insists that he isn’t always hungry. “I eat whenever I feel like it,” he says. Instead of reaching for a cookie for a snack, however, he crunches a carrot or a red pepper. At restaurants, he sticks with appetizers or a first-course salad. His girlfriend, a marathon runner, also follows a CR diet, which probably helps him stick with the program.
There are downsides. Calorie restriction reduces testosterone levels, which in men can mean lower libido. (Researchers don’t have much data about the way CR affects female hormones.) Voss is now so thin that sitting on a hard chair gets uncomfortable. But he insists he still has all the energy he needs to work the 14 hours a day required by his company, and to squeeze in an hour or so of power walking most days.
Not everyone thinks CR will buy Peter Voss much extra time. Recently, John Phelan, Ph.D., a researcher at UCLA, published a mathematical model predicting that calorie restriction is likely to offer at best a 7 percent increase in human life expectancy. As evidence he pointed out that the average Japanese male consumes about 2,300 calories a day. Men on Okinawa consume about 17 percent fewer calories—very close to Peter Voss’s 1,850 a day—but they only live a little less than a year longer than Japanese mainlanders. Calorie restriction may have its most dramatic effects in species that have experienced periodic famines, forcing them to evolve extreme measures to shut down reproduction and focus on staying alive until food supplies return. We humans, naysayers argue, aren’t likely to be among them.
Still, many researchers are excited about the potential benefits. In August, just back from an Experimental Biology conference where the latest findings on CR were presented, Susan Roberts, Ph.D., who is directing a calorie-restriction experiment at Tufts University, wrote in an e-mail: “The human data on people who are already doing CR themselves is extremely impressive. I was sitting in the meeting virtually ready to sign up…myself!”