A woman subsists on 900 calories a day. A six-foot-tall stick figure of a man weighs 115 pounds.
These are not victims of famine or anorexia, but high-functioning Americans seeking longer, healthier lives by eating a nutritious yet meager diet that forces their bodies to continually function on the brink of starvation. In return, they hope to extend their lives by years, if not decades.
Such a self-abnegating lifestyle that promises so much smacks of new age prophecy: Kool-Aid for a cult of waifs. Yet scientific evidence supporting the diet—rather blandly referred to as Calorie Restriction—continues to mount.
Science of Starvation
The theory dates back to 1935 when Clive McCay, a nutritionist at Cornell University, discovered that mice consuming 30 percent fewer calories lived 40 percent longer than mice that ate as they pleased. Since then, countless experiments with mice as well as with yeast cells, worms, and spiders have bore similar results. Recent findings on rhesus monkeys offer the greatest hope for humans. The monkeys that have been on Calorie Restricted (CR) diets for twenty years were less likely to die of age-related illnesses and retained better brain capacity for decision-making and controlled movement than their unrestrained counterparts.
No one has figured out why sharply decreasing calorie consumption and lowering metabolic activity would promote longevity. One leading explanation theorizes that nearly starving the body thrusts it into a maintenance mode; it concentrates on staying healthy and preserving its cells as opposed to say, breeding. (A lowered libido is considered a common side effect of an extremely low calorie diet.)
A Calorie-Deprived Movement
After conducting his own CR mice experiments in the 1960s, UCLA Professor Roy Walford became convinced that a restricted diet was the key to living longer. He wrote the CR bible, Beyond the 120-Year Diet: How to Double Your Vital Years, and in 1994 he and others founded the Calorie Restriction Society.
Loosely defined, a CR diet cuts caloric intake by 30 percent. A man practicing CR might eat about 1,800 calories a day, 900 calories less than an average American male. Walford’s own 1,600 calorie a day diet typically consists of a breakfast of a low-fat milk shake, a banana, some yeast and berries, a large salad for lunch, and a small portion of fish, a baked sweet potato, and some vegetables for dinner. Lean and muscular into his seventies, he was 5'8" and weighed just 134 pounds. But the stringent diet was not his elixir for an extraordinarily long and disease-free life. In 2004, he died from Lou Gehrig’s disease at seventy-eight.
Walford’s death did not deter CR disciples. The CR Society claims some 3,000 members.
Positive Results, Yet Doubts Remain
So far, physiological tests on Calorie Restriction practitioners indicate that they are much healthier than the average American and may even have at least one advantage over long distance athletes. CR followers have fewer predictors of age-related diseases, lower levels of the so-called bad cholesterol and more of the good stuff, as well as lower blood pressure. One study found the dieters’ hearts functioned as if they were fifteen years younger.
Not everyone is convinced, though. Some scientists argue that such a severe diet can have harmful effects. In the study of rhesus monkeys, several died from factors that were not age-related but may have been caused by eating too little. In another experiment that tested the CR theory, the restricted diet prolonged the lives of “chubby” mice—a strain that was genetically manipulated to gain weight over their lifetime—but didn’t have any effect on lean mice. That suggests that there may be a flaw in many of the human studies that compare the CR dieters with average Americans. Since two out of every three Americans are overweight, it would be shocking if the dieters were not healthier. If they were compared to lean Americans who ate a moderate, nutritious diet, would the disparity still exist?
Even among diehard Calorie Restriction believers, severely limiting calories is an unsavory proposition. Scientists are working on developing other painless methods that mimic the beneficial effects of a Spartan diet. Researchers are studying resveratrol, a compound in red wine, that may trick the body into thinking it’s starving. But results so far are ambiguous. Obese mice seem to live longer on resveratrol, but lean mice don’t. Rapamycin, a drug used in organ transplants, has also boosted the life span of mice, but it suppresses the immune system, which runs the risk, paradoxically, of causing illness and death.
If these more palatable methods fail and a harsh diet proves the most promising strategy for living longer, it’s still unlikely that Americans will jump on the CR bandwagon. After all, it’s not only a hungry life, it’s potentially a very lonely one. Eating with friends and family and dining in restaurants gets stressful when counting calories is a matter of life and death. And shrunken bodies and libidos bode poorly for romantic relationships. Whether the extra years are worth the diligence and depravation might depend on how they’re spent.
Updated February 25, 2010