The thing about dining with Tristan Bettencourt is that it doesn’t involve much eating. An icy rain barrels down outside the cozy cafe where he’s a regular, making the prospect of the warm meal laid out in front of him that much more inviting: a mug of hot tea, a bowl of dal, a plate loaded with steamed vegetables and brown rice. He prods the food cautiously with his fork. “This pile of veggies is almost irrelevant calories,” he says. “I won’t eat most of the rice.”
Waistline watcher? Carb counter? Nope, that’s for amateurs. Bettencourt is on a diet that never ends. And when he says he intends to keep doing something forever, he means forever.
Bettencourt, along with fellow members of a group called the Calorie Restriction Society, has dramatically curtailed his diet in a bid to extend his life. He’s not settling for vitamins or daily workouts — those things may help prevent premature death, but do nothing to actually extend the human lifespan, which tops out around 120. No, calorie restrictors hope to push back death’s deadline. They envision future generations of people who breeze past the big 1-2-0 with the blush of youth still upon them. The secret, they believe, based both on pop science and decades of basic lab research, is eating less — a whole heck of a lot less.
For the past dozen years, Bettencourt has kept his daily food intake to about 70 percent of what he figures he’d otherwise consume. He currently eats around 1,500 calories a day, less than half of the 3,200 calories the US Food and Drug Administration considers normal for a moderately active man. And it shows. The 48-year-old looks like a yogi — extremely thin, sinewy almost. His suit hangs off his frame a little, and his fingers are slim and pale like a surgeon’s. At five foot nine, he weighs just 118 pounds, seven pounds short of the minimum federal “healthy” weight for someone of his stature. Yet Bettencourt boasts that he hasn’t had a cold or the flu in fifteen years, that he hiked Mount Whitney in a single day this past summer with no problems, and that he has fantastic energy. “Race you around the block any day,” he challenges.
Bettencourt has weighed as little as 112 pounds, but says it made him moody, gave him panic attacks, and left him so emaciated that people would ask if he was HIV-positive. A health plan even denied him enrollment, certain that his low weight signaled a serious undiagnosed condition. Despite all this unpleasantness, Bettencourt still wonders if he should aim closer to his discomfort threshold. “I almost feel like if I want to be really true to my fundamental philosophy, I should be eating just enough to keep myself at 112.5,” he says. Central to his philosophy is a refusal to go gently into that good night. Like many of his fellow calorie restrictors, Bettencourt, a college biology major now employed as an analyst for the San Francisco Taxi Commission, is driven by a fierce conviction that this mortal coil is all there is. “I don’t want to get decrepit and die,” he says bluntly. “When my consciousness ceases, the universe ceases, as far as I’m concerned. I guess I have an overblown survival instinct. I decided that there is nothing more important than life, so I should do what I could to prolong it.”
Bettencourt has always been pretty health-conscious — he’s a longtime vegetarian and an avid yoga practitioner — but says he was inspired to take up caloric restriction by an early sign of aging: a receding hairline. “What most of us in our little calorie restriction group are hoping for is to kind of bootstrap our way to immortality,” he explains. “The hope is that calorie restriction will be the first step that gets us to survive long enough to benefit from unknown future technologies which will then take us to the next step.”
The society, which was founded in 1995 and claims roughly 1,800 members, was inspired by the writings of Dr. Roy Walford, a UCLA pathologist best known for his stint in Biosphere 2, a glass enclosure built in the Arizona desert to test whether humans could live in a self-sustaining artificial environment. During a two-year trial launched in September 1991, food supplies inside the structure ran precariously low, but Walford convinced the others to stick it out on an extremely low-calorie diet. Although the residents looked calamitously thin, tests indicated that aspects of their health were actually improving — in particular, they had lower blood sugar and cholesterol levels. Walford later dedicated himself to popularizing calorie restriction and wrote a series of influential books, including one called The 120-Year Diet.
But there’s more to it than celebrity science. Years of studies have shown that severe dietary restriction indeed prolongs life, in lab creatures at least. Yeast on a starvation diet can live up to three times longer than normal, fruit flies double their average lifespan, and mice that normally live two years can live three or more. Studies on monkeys are ongoing, since primates are naturally long-lived, but so far the calorie-restricted monkeys appear to get fewer lethal chronic diseases and may indeed outlive their well-fed peers.
These animals not only live longer, but seem to retain their youthfulness. They are smaller than their counterparts, but more active. They look younger and healthier, are mentally more agile, and have bolstered immune-system activity. The results suggest that eating far less might prevent or slow the onset of a host of human age-related conditions such as cancer, diabetes, heart disease, and Alzheimer’s and Parkinson’s diseases. The observed changes occur quickly and bring longevity benefits at any age.
A study appearing this week in the Journal of the American College of Cardiology suggests that at least some of these health benefits apply to humans, too. Led by St. Louis researcher Luigi Fontana, the authors measured diastolic heart function in 25 members of the Calorie Restriction Society aged 41 to 65, who had been eating nutritionally balanced diets of 1,400 to 2,000 calories per day for an average of six years. The subjects were compared with a control group of 25 people who ate a typical Western diet of 2,000 to 3,000 calories. The restrictors’ hearts, the team reported, behaved like those of much younger people — fifteen years younger on average. Fontana, a regular speaker at Calorie Restriction Society conferences, stressed in a statement that merely eating less isn’t enough. The calorie restrictors aim for a traditional Mediterranean diet, which includes a wide variety of vegetables, olive oil, beans, whole grains, fish, and fruit, and avoids refined and processed foods, soft drinks, desserts, white bread, and similar “empty” calories.
Yet any reader tempted to start fasting tomorrow should be advised that nobody yet knows exactly how this biology works, or whether the eye-popping longevity results similarly will apply to humans. While scientists have observed the effects of caloric restriction in lab animals since the 1930s, our seventy-plus-year human lifespan, not to mention our fondness for eating, makes most people poor research subjects.
Some nutritionists, meanwhile, consider such severe dieting foolhardy, liable to cause all sorts of medical problems for people who attempt it ad hoc — the Calorie Restriction Society, which tends to attract obsessive food types, has been accused of promoting anorexia or exacerbating the obsessive-compulsive traits of its members. Calorie restriction also makes mammals perpetually hungry and cranky, which doesn’t bode well for recruiting study volunteers.
Yet none of this has discouraged scientists and venture capitalists bent on discovering the molecular fountain of youth. Over the past decade, a host of companies has emerged, hoping to capitalize on recent advances in our understanding of aging. While a secret anti-aging potion has proved elusive, the last few years in particular have seen an explosion of research as scientists in the Bay Area and elsewhere begin to elucidate the genetic and cellular processes triggered by food deprivation.
Some would say we’re on the cusp of a second modern revolution in human longevity, the first being advances in nutrition and health care that have allowed more people to reach old age. The second revolution, ostensibly, would succeed in delaying the onset of old age and further extending human lifespan.
It may in fact be too early to deem the recent developments a “revolution.” But Dr. Marc Hellerstein, a Cal biochemist and nutritionist whose lab has produced provocative new research on how calorie restriction may inhibit diseases like cancer, reports that we’re finally getting close to some explanations for the changes triggered by food deprivation, changes he calls “the most remarkable unexplained observation in modern biology.”
What’s more, recent studies suggest there may be ways to trigger a longevity response without resorting to full-blown calorie restriction.
Unlike the calorie restrictors, and even some of his research colleagues, Marc Hellerstein is no true believer. His entry into the field, in fact, was something of a detour. Hellerstein’s background is in endocrinology and nutritional biochemistry, and until recently his focus was AIDS research. He’s neither bent on extending his own life nor keen to start skipping meals. A dedicated runner, the professor is whippet-thin and constantly clad in puffy white track shoes, although he’ll cheerfully admit that exercise alone won’t extend his allotted threescore and ten. He’s fond of quoting the rueful saw of calorie restrictors everywhere: “You may not live forever, but it’ll sure seem like it.”
Yet Hellerstein is duly impressed by the changes he’s observed in his food-deprived lab mice. “These animals look better, they have sleeker coats, they have better immune systems, they don’t get diseases, they live longer, they don’t get cancer — I mean, it looks like kind of a miracle intervention,” he says.
Why might food deprivation make some species live longer? A basic theory Hellerstein shares with many of his colleagues is that most animals are hardwired to deal with periodic food shortages. Scarcity may kick in a genetic or hormonal “conservation” reaction designed to prolong life until food is available, hopefully giving the animal another shot at breeding. “All mammals are spectacularly efficient at starving well,” Hellerstein says. “It’s one of the most orchestrated things in the whole mammalian repertoire — it’s brilliant!”
Within three to five days after a person stops eating, he says, nearly every organ in the body becomes involved in an intricate chemical choreography to maintain muscle mass while slowing growth and improving energy efficiency. The muscles get more efficient at burning fat, the liver stops producing glucose — the brain switches over to another energy substrate — and thyroid and growth hormone levels drop so the body uses less energy and its cells divide less frequently. Food-deprived animals also become much more active and quicker to learn. This, some researchers hypothesize, may help them hunt for food more vigorously — scientists have observed similar hyperactivity in anorexic humans. Thanks to this built-in cycle of self-preservation, people can survive up to three months without food. Otherwise, Hellerstein says, we’d perish in three to four weeks.
For our forebears, Hellerstein points out, obesity was simply not an option. Prior to the relatively recent invention of farming, our human ancestors would have had an extremely low-calorie diet largely based on foraging for plants in season. Even the animals they ate were lean and wild, not the farm-fattened pigs and cows we grill today. And while our predecessors consumed natural sugars — from fruit, for instance — they never would have horked down a Twinkie. If anything, Hellerstein says, we’re now suffering from overnutrition as a result of highly processed, calorie-dense foods. As a result, he says, we tend to die prematurely: “We don’t die of cold exposure, we don’t die of getting attacked by a leopard or a saber-toothed tiger, but we do die of diseases of consumption and a sedentary lifestyle.”
Mortality data supports that contention. America’s leading killers at the turn of the last century were influenza, tuberculosis, and pneumonia, but according to a recent status report on aging from the Centers for Disease Control, this century’s top killers so far are conditions linked to aging and consumption: heart disease, cancer, and strokes. We’ve won the battle against many infectious diseases, only to lose the war against milkshakes and ranch dressing.
Lab mice, who live similarly protected, sedentary, and overfed lifestyles, tend to die of like afflictions, particularly cancer and kidney failure. Perhaps the reason calorie-restricted lab mice live so long, Hellerstein theorized, is that eating less somehow slows the onset of these diseases. Using a new technique he developed, Hellerstein and Elaine Hsieh, then his graduate student, were able to show that restricting the food intake of lab mice leads to much slower growth rates for skin, breast, and white blood cells. This translates to a slowdown in tumor growth. “It makes sense,” Hellerstein says. “Why would you waste energy and grow and divide cells and turn over cells if you can’t even feed yourself?”
Consequently, they realized, calorie restriction may even halt or delay the onset of cancer. After all, Hellerstein notes, cells have to divide for our bodies to fix daily wear and tear, but that can create problems. “It’s a dangerous thing to divide,” he says. “Every time a cell divides there is chromosomal damage that could happen.”
It’s even more dangerous for a cell to divide rapidly and often, because if the cell splits before it has fixed existing DNA damage, those genetic mutations get passed on to the daughter cells. And if the cells continue to mutate and divide before the errors are fixed, four or five divisions later the cells become cancerous. Slowing down cell proliferation makes this less likely.
Mark Mattson, a neuroscientist at the National Institute on Aging who also researches calorie restriction, believes eating less may slow cancer by triggering a hormonal reaction. “Levels of insulinlike growth factor and levels of insulin are decreased, which is a good thing,” he explains, because the former hormone is known to promote the growth of cancer cells. Mattson points out that calorie restriction also bolsters immune-system agents that course through the body removing DNA-damaged cells, another step in thwarting cancer. And reducing insulin levels has profound implications for another common age-related killer — diabetes.
Mattson’s own research aims to clarify how calorie restriction inhibits degenerative brain disorders such as Alzheimer’s and Parkinson’s diseases, which are becoming more common as people live longer. One theory, he says, is that the stress of fasting is analogous to physical exercise. “When you’re exercising vigorously, it’s a stress on your cells, your heart muscles, but they respond in an adaptive way,” he says. “We have pretty good evidence that when the nerve cells are exposed to a mild stress it activates genetic programs that help them resist more stress.”
Helping stave off age-related diseases is one thing, but could calorie restriction somehow put the brakes on aging itself? Bruce Ames, a senior scientist at Children’s Hospital Oakland Research Institute, longtime Cal professor, and leader in aging research, promulgates the widely accepted idea that mitochondria are key to how fast our bodies wear out. These subcellular power plants are where we consume oxygen and convert food metabolites into molecular fuel our bodies can use. But like cell division, Ames notes that this process, which strips electrons from molecules, is also dangerous. Some of the electrons invariably go astray, resulting in highly reactive oxidants called free radicals that damage the surrounding DNA. This happens more frequently as cells age. “As you get older, you’re making more and more oxidants in your mitochondria — it’s like an old car engine that’s leaking out more black smoke and is more inefficient,” Ames says. That means more DNA damage, which leads to breakdowns that cause disease and what we call aging.
Calorie restrictors approach this problem with some simple math: Less eating means fewer nutrients to burn, which means fewer free radicals and slower aging. Ames himself believes some of the mitochondrial damage can be mitigated with multivitamins and a well-balanced diet. In 1999, he founded Juvenon, an Orinda company that sells a dietary supplement of the same name — a combination of acetyl-L-carnitine and alpha-lipoic acid designed to maintain mitochondrial health.
But scientists also wonder whether food deprivation kicks in an even more fundamental self-preservation reaction: activating genes that extend lifespan. Dr. Su-Ju Lin, an assistant professor of microbiology at UC Davis, has seen remarkable results in yeast. She found that food deprivation caused changes in genes called Sir2 and Hst2 that increased the cells’ metabolic efficiency and allowed them to live three times longer than normal. (Although single-celled organisms, yeast are genetically closer to humans than they are to bacteria.)
Likewise Cynthia Kenyon, a biochemist at UC San Francisco and another pioneer in longevity research, has produced genetically mutant roundworms that live up to six times the standard lifespan. Her experiments targeted a gene called daf-2 that seems to regulate a host of longevity-related processes — including turning on genes that help the organism resist free-radical damage and act as blueprints for “chaperone” proteins that fix damaged cells. Daf-2 also controls a growth-signaling system in worms that works much like a human system involving hormones insulin and insulinlike growth factor, which Kenyon believes play a crucial role in aging. Calorie restriction researchers embrace Kenyon’s work because it, too, links longevity to slower cell growth and reduced free-radical damage.
Lest you wonder what yeast and worm genes have to do with people, Lin and Kenyon explain that most species, including humans, have genes very similar to the ones they are investigating. Scientists use simpler organisms like yeast, roundworms, and fruit flies because their genes are easy to manipulate. In fact, Kenyon believes there’s a master aging-control apparatus embedded in the genes of every species. “My idea is that in all animals it would be the same, but it would be set to run differently in different animals,” she says. “Mice have, say, a two-year lifespan and bats a fifty-year lifespan, and they are both about the same size. That tells you that obviously genes influence aging enormously.”
If calorie restriction works by tripping “longevity” genes, it may be possible to develop a drug that mimics its effects without the harsh diet regimen. While it would be hard to sell the FDA on claims of human life extension, Lin says, a drug mimicking calorie restriction could have enormous potential as a treatment for diabetes or cancer. Kenyon, meanwhile, is cofounder of Elixir Pharmaceuticals, a company that aims to pinpoint the control mechanisms of aging and metabolism and develop drugs that affect the process. “We’re not talking about genetic engineering here — it’s a pill, kind of like a vitamin that would make you live longer,” Kenyon speculates. “That’s not to say we know how to do that. We don’t.”
Since this wonder pill is still entirely theoretical, and most people would find a lifetime of fasting unpleasant, might there be an easier way to trick your body into extending life?
Perhaps. In 2003, Mattson had a brilliant revelation. As a matter of course, the test animals in most published calorie-restriction studies were fed every other day, presumably because it made life easier for graduate students. But what if that intermittent feeding pattern, not the severe diet, was triggering the results? Mattson promptly devised a study wherein rats had access to all they could eat on every other day, and nothing during the intervening days. The striking result: The rodents behaved much like their calorie-restricted counterparts in prior studies. Their glucose metabolism improved — blood sugar and insulin levels dropped — and so did their stress response. This, Mattson surmised, signaled diminished free-radical production and an enhanced ability to deal with stress, both keys to longevity and disease prevention. (Low blood sugar thwarts diabetes, while the ability of the heart, blood vessels, and brain to resist stress protects against heart disease and strokes.)
Hellerstein and Hsieh went on to show that intermittent feeding may have a similar effect in thwarting cancer. They fed mice on alternating days, with one group getting just short of the standard lab diet, while the other mice ate 33 percent less. Remarkably, the well-fed mice showed nearly the same slowdown in cell proliferation as the severely restricted group. The researchers concluded that the biological trigger had to be the intermittent fasting, not the overall food intake. “That was stunning to me,” Hsieh says.
And yet it rings true, Hellerstein says. In the wild, nobody is guaranteed a daily meal. Carnivores in particular have a built-in schedule: hunt, pig out, sleep it off, fast, repeat. Humans are no different, Mattson agrees. “Our genetics are geared towards going for extended times without food,” he says. “Our ancestors never had a refrigerator in their house — they had to go out and find food, and depending on the season of the year they might have had trouble.”
Instead of starving, Hellerstein and Hsieh say, perhaps a partial fast on alternating days will prove enough to trip the self-preservation response in humans. “We had been thinking about it as kind of a preserve-your-body-in-the-most-crude-way response: Don’t die now,” Hellerstein says. “Unknowingly, we stumbled upon the fact that you can exploit this starvation response for therapeutic benefit because it’s so potent and so brilliantly conceived. We evolved to be so excellent at this that you can maybe even exploit it intermittently.”
Reducing food intake every other day, of course, is a gentler proposition than full-blown calorie restriction, and it’s something cancer or diabetes patients might be willing to try as a therapy if it’s shown to limit human cell growth and insulin production. Indeed, several studies of alternate-day fasting are under way, and Hellerstein is proposing a collaborative project to measure cell proliferation rates in alternate-day fasters. The only research published to date, however, suggests that some refinement may yet be in order to make the diet more palatable. The authors noted that going without food on every other day is medically feasible in the short term, but participants reported being crabby and hungry all the time, and lost weight even if they didn’t intend to. The researchers concluded that people might be happier if they could eat one small meal on their fasting days.
Some people are already trying the latter variation. Since he published his rat study in 2003, Mattson says he’s gotten e-mails from around fifty people claiming to have tried it with positive results. One is Dr. Donald Laub, now retired from his post as chief of plastic and reconstructive surgery at Stanford University Medical Center. Laub has always been an adventurer — he helped pioneer sex-change operations and later founded Interplast, which sends surgeon volunteers to operate on poor children with congenital deformities. Now 71, and having survived a battle with lymphoma, he has decided to devote what he calls his “second life” to healthier living. After reading Mattson’s article, he made himself an independent guinea pig for the every-other-day diet.
Laub had previously tried straight calorie restriction, but quickly dropped it. “You get ornery,” he says. For the past year, he has alternated days where he eats as much as he likes with 500-calorie days. As a physician, he’s aware of both the benefits and drawbacks, and readily admits it’s not easy. To overcome hunger, Laub says he relies on a variety of psychological tricks. For example, he keeps a package of instant shake mix nearby that he knows he can eat in an emergency — when he feels a hunger pang, he tries to “postpone” it by ten minutes in the hope that it will pass. He deals with going to bed hungry by making lists of what he’ll eat the next day. “I’ll think, ‘Tomorrow morning I’m going to eat sausage, cheese, fried eggs, and bacon,'” he says. “That helps me get over it. The next morning I wake up and I don’t want to eat anything.”
Nevertheless, he’s convinced his diet is much more feasible than daily calorie restriction, and intends to do it for the rest of his life. Laub has dropped forty pounds and says he’s gained a great deal of energy, particularly on fasting days. “After you go through five or ten down days, you relish them. On the down day you have much more energy, you have an obsessive-compulsive tendency to do obsessive-compulsive things like clean the desk drawers and get the files in order,” he says. “You have actually more stamina and more energy. These characteristics are also in anorexic patients, I must admit.”
Laub isn’t the only one to notice the similarities. On its Web site, the Calorie Restriction Society takes great pains to distinguish between what it endorses and eating disorders. The society’s goal is longevity, not weight loss, the site says, and to forge a healthy relationship with food, not an oppositional one. “We don’t want people who are extremists, who isolate themselves or adopt freak starvation diets,” says the group’s secretary, Warren Taylor. He adds that nobody should try calorie restriction without consulting a doctor and easing into it slowly. Bettencourt, for instance, took three years to ramp up to full speed.
But the site also admits that members have experienced anorexia, binge eating, and obsessive thoughts about food. Nancy Hudson, director of the dietetics program at UC Berkeley, agrees that calorie restriction would be an awfully appealing justification to an anorexic, or to someone with orthorexia, an obsession with food “purity” and healthy eating that can actually push people to unhealthy extremes.
After all, Hudson says, eating too little can be dangerous. Her main concern is a diminished immune response to ordinary infections like the flu — a worry Hellerstein says is more applicable to malnutrition — and slow recovery from injuries, since the body needs protein to heal. Women whose body fat drops below 10 percent are at risk for losing their normal estrogen function and menstrual periods, which, in turn, puts them at risk for osteoporosis and bone breakage. It goes without saying that such a diet would be perilous for anyone in a growth stage, including pregnant women, children, and teens. Hudson says dieticians sometimes see cases of what she calls middle-class malnutrition. “We see this in kids where parents are so concerned about fat that they put their kids on low-fat diets before they’re old enough, and then you end up with failure to thrive, or growth failure secondary to nutrient deficiency,” she says.
The Calorie Restriction Society cites these problems and more — anemia, cold sensitivity, depression, and emotional deadening — that are sometimes associated with dramatic weight loss. There are also tales of marriages strained by one spouse’s sudden body change, preoccupation with food, or loss of libido — a frequent side effect of low body weight in men. And in a society where family and social lives revolve around food, a rigorous diet can produce a lot of stress. “People take it personally when you don’t eat their food,” Bettencourt admits. “They give you all this crap food to eat and they sit there smiling at you expectantly. Then they think that you’ve got some kind of compulsive eating disorder, and really you just don’t want to eat their low-quality food or that amount of food.”
Ultimately, calorie restrictors think it’s more risky to eat like a typical sugar-and-fat-guzzling American, and that calorie restriction is pleasant enough once you’ve weaned yourself off junk food. Taylor, who has been restricting for six years, says he far prefers a substitute ice cream made with micronized cellulose and guar to one made of sugar and cream. “If your mindset is squared away, you cannot enjoy standard ice cream — you can’t,” he says. “You emotionally find it very troubling. A calorie-restriction person’s mindset is so strongly oriented towards healthful living that they can’t eat bacon — it would be stupid to eat bacon! It would be stupid to eat cheesecake, because it’s devastating to longevity.”
But given the lack of human longevity studies, what do the researchers make of calorie restrictors? “I can’t say it’s a bad thing,” Hellerstein shrugs, “but they’re kind of ahead of the evidence.” For his part, Mattson points out that in nearly all of the studies so far, animals that are kept close to the body weight they’d normally have in the wild show only modest health and lifespan improvements under calorie restriction. But they are much healthier and longer-lived than the control group, consisting of animals that are allowed to eat without limit and are essentially very fat. This, the scientist says, indicates that calorie restriction will have its most profound effect on obese animals, including obese humans. Given that nearly two-thirds of American adults are overweight, that’s an intriguing distinction. “I’d say it’s a fountain of youth for overweight people,” Mattson muses, “but for normal-weight people, I don’t think there’s any compelling reason to start severely restricting their caloric intake.”
Although life may seem fleeting, humans actually live a relatively long time. “Longevity is an integral part of our species. It’s as important as bipedalism and a large brain,” says Dr. James Carey, senior fellow at UC Berkeley’s Center for the Economics and Demography of Aging. We’re a highly social species with a long childhood during which we are completely dependent on others — that means parents must survive long enough to raise their offspring to independence. If humans died soon after producing babies, Carey says, “You’d have a hominid concept, but you wouldn’t have our humanity.”
Furthermore, Carey says, grandparents play a key role in providing childcare and passing down wisdom between generations. Just as elephant matriarchs are “walking libraries” for their herds, human elders in preliterate societies preserved technical knowledge such as how to make tools, find food, and survive under adverse conditions such as floods or droughts that might occur just once per generation. All of this provided selective advantages to groups of people who naturally lived longer.
On the other hand, UCSF’s Kenyon asks, “Why don’t we already live to be two hundred? Well, is it really necessary to have great-grandparents around if you have the grandparents? Are there really things you need to remember that go back two hundred years?” Death, after all, is crucial to the survival of a species. It ensures population turnover that diversifies the gene pool and the social structure, and keeps the society flexible enough to adapt to new environmental conditions. It also prevents organisms that are sick or beyond their reproductive prime from consuming resources better used by the young. For instance, Kenyon notes, it’s in the best interest of her roundworms to be extremely short-lived. The worms are hermaphrodites that take only three days to mature and another three to produce three hundred progeny. There’s no evolutionary point, she says, in having the older worms compete for food with their genetically identical offspring.
Researchers differ on whether there’s any sort of hard limit on human lifespan. Modern medicine certainly led to a drastic increase: Life expectancy of an American born in 1900 was only 47 years, while a baby born in 2001 can expect to reach 77. But these are just averages. The oldest known human lived to 122, and that ceiling has shown no sign of changing for hundreds of years. If calorie restriction can break this barrier, we won’t know it until folks like Bettencourt start blowing out the candles on their 130th-birthday lentil loaves.
Whether that would be good or bad depends on perspective, but the concept of life extension poses profound questions related to social order. Are we going to have a generation of decrepit 120-year-olds, barely clinging to consciousness? It’s easy to imagine the potential health-care, Social Security, and population-control nightmares created by a generation of übercodgers. After all, the CDC reports, the average American 75-year-old has three chronic conditions and uses five prescription drugs — we’re hardly a superspecies.
Or could we, on the other hand, produce what Cal’s James Carey terms the “salmon model,” in which we’ve eradicated so many diseases that the very elderly won’t even get sick before they die, but transition almost instantly from health to death? Hellerstein and Hsieh speculate that calorie restriction may bring not only longer life, but a healthier old age, since it appears to postpone so many chronic diseases. “Then,” Hsieh says, “the conditions that we see at age eighty maybe don’t occur until age one hundred.”
In general, the researchers tend to be more excited by calorie restriction’s potential than troubled by its implications. “For most of human history, forty years old was an old man,” Ames says. “Since the Industrial Revolution and modern capitalism, we have been getting longer and longer life expectancies, and of course this is unnatural — the natural thing is to die at forty! I don’t think there’s anything wrong with it. We’ve adapted to this 25 extra years of life, and we’ll adapt to another 50 years or whatever it’s going to be.”
“We always fight against evolution,” Hellerstein concurs. “We do that as physicians all the time. That’s our job, to be smarter than nature.”
Nature, however, is pretty good at outsmarting us. Even the most ardent calorie restrictor knows there are no guarantees — there’s always the possibility of an errant city bus or falling anvil. Calorie Restriction Society inspiration Roy Walford spent much of his life trying to elude death, but it found him anyway. In 2004, he succumbed to amyotrophic lateral sclerosis, better known as ALS or Lou Gehrig’s disease. He was 79, far short of the desired 120, and while Walford blamed his affliction on oxygen deprivation suffered in Biosphere 2, Mattson has another theory based on his studies. “The one neurogenetic disorder we found that could be worsened by caloric restriction was ALS,” he muses. “It kind of seems like an interesting coincidence.”
Since the future is guaranteed to no one, most people would rather focus on the pleasures of the present. In our culture, that often means food: holiday dinners, birthday cakes, invitations for a beer or a slice with some friends. “There are some people who will clearly say, if that’s what it’s going to take to live a long time, I don’t want to live a long time — I would rather eat my steak and have butter and gravy and die at sixty than live to seventy,” says Hudson, the dietician.
Yet simply because you eat less, Bettencourt says, doesn’t mean food can’t be pleasurable. “That ability to really relish what you’re doing is independent of the thing you’re relishing. You might love a big bowl of ice cream, I might love two blueberries,” he says. “Teach yourself to enjoy whatever is good for you and you’ve got it all.”
Even longevity experts find themselves torn over whether to practice what they research. Kenyon sticks to the low-carb South Beach diet, and while she doesn’t consider herself a calorie restrictor, she eats less than she used to. Ames, who recently turned 77, follows a Mediterranean diet and takes both a multivitamin and his Juvenon supplement. Lin says she has no interest in restricting her diet while she’s working — “I can’t think when I’m hungry,” she says wryly. And Hsieh says she’ll consider restricting only if, heaven forbid, she’s diagnosed with diabetes or cancer.
As for Hellerstein, the 54-year-old prof will stick to running. “I don’t want to be miserable so I can live four extra years, or ten extra years,” he says. “On the other hand, if it really was true that you could eat 25 percent or 30 percent less every other day and live ten more years, would I do that?” He scratches his chin thoughtfully. “I’ll have to think about that.” The researcher then gets up to root around in a bowl of candy he’s been picking through all afternoon. “Just because you study caloric restriction,” he says, popping one into his mouth, “doesn’t mean you can’t eat an Atomic Fireball.”
Editor’s note: This story has been corrected since it first appeared. Tristan Bettencourt is 48, not 38.