The quest for eternal life is as old as death. Searching for the fountain of youth fired the imaginations of explorers and writers for centuries, to no avail. Today, in a variation on a theme, scientists pour their energies into exploring the idea of life extension: living longer by eating drastically less. Calorie restriction (CR) is the buzz phrase: a theory that a nutritious, but extremely low-calorie, diet will extend the life of lab mice, research monkeys and perhaps humans. It gained much of its popular public acceptance through the work of Roy Walford, a California researcher, gerontologist and author of the bestselling Beyond the 120-year Diet: How to Double Your Vital Years.
Walford espoused the idea that you, like him, could live a more vigorous life on just 1,600 well-chosen calories a day. He began linking food to longevity in the 1960s when he restricted the diet of mice by 40 per cent. He reported their lifespans doubled. Walford wasn’t as lucky. He died at 79 of ALS, commonly known as Lou Gehrig’s disease.
For more than 20 years now, the poster primates for CR have been two peckish troops of rhesus monkeys, one at the University of Wisconsin at Madison and a second group of involuntary dieters at the U.S. National Institute on Aging (NIA) in Baltimore. At best, the results of these experiments are mixed and the latest news suggests the fountain of youth is as elusive as ever.
A 23-year study by NIA researchers published Aug. 29 in the online issue of Nature found monkeys fed 30 per cent less food did not live longer than a control group fed a standard healthy diet. “However, calorie restriction did extend certain aspects of health.” Complicating matters is a 2009 Wisconsin study that found 13 per cent of the monkeys on limited diets died of age-related causes, compared to 37 per cent of the control group. The Wisconsin control monkeys, however, were fed an unlimited and unhealthy diet, while the longer-lived control group in the NIA experiment were limited to the equivalent of a normal diet of healthy natural foods. Some scientists postulate the Wisconsin experiment says more about the risks of an unhealthy control group than about the benefits of a restricted diet.
Still, there is good news for those hungering to live a healthier, if not longer, life. Both studies found certain age-related diseases, such as diabetes, arthritis and cardiovascular problems, arrived later in life for those on restricted diets. There was also “a significant reduction” in cancer if calorie restriction started at a young age.
Whether diet can trump genetics, how semi-starvation triggers animal health outcomes and what any of that means for human life expectancy remain largely unexplored questions. Dr. Samir Sinha, director of geriatrics at Mount Sinai and the University Health Networks hospitals in Toronto, notes a recent study in the British Medical Journal found a complex web of factors impact longevity. Older people can live up to five or six years longer merely by not smoking, being physically active and having a strong social network.
“I think the greater nemesis of old age currently is unintentional weight loss,” says Sinha. Depression, isolation, poverty and the impact of medication all contribute to weight loss, as does a “fat phobic” culture, he says. “They have been taught for so long to avoid foods with fat or cholesterol that they restrict their diets, which only further enhances weight loss.” Sinha has taken to advising some elderly patients to eat daily bowls of ice cream as a meal supplement, writing it on a prescription pad to make it more authoritative.
Eating well and in moderation is key. “Too much of a good thing can be harmful, we all know that,” Sinha says. “Too little isn’t always a good thing either.”