Low-calorie diet may lengthen life
Regimen reduces risk of diseases associated with aging
By Rob Stein
Updated: 12:29 p.m. ET April 20, 2004
A small group of people who are drastically restricting how much they eat in the hope of slowing the aging process have produced the strongest support yet for the tantalizing theory that very low-calorie diets can extend the human lifespan.
The first study of people who voluntarily imposed draconian diets on themselves found that their cholesterol levels, blood pressure and other major risk factors for heart disease -- the biggest killer -- plummeted, along with risk factors for diabetes and possibly other leading causes of death such as cancer and Alzheimer's.
"These people are definitely protected against the major killers," said John O. Holloszy of Washington University School of Medicine in St. Louis, who led the study, released online yesterday. "It should definitely increase longevity."
While it has long been known that eating well and staying trim helps people live healthier lives and avoid dying prematurely, evidence has been accumulating that following extremely low-calorie diets for many years may do something more -- significantly extend longevity beyond current norms.
Lab rats, mice and other creatures live much longer when fed very low-calorie diets, and some researchers suggest the same Fountain of Youth effects may hold true for people, perhaps by cutting the body's production of harmful atoms or molecules known as free radicals. But aside from a few corroborating clues from historical records of famines, the only evidence from humans came in 1991, when eight subjects in the sealed Biosphere laboratory in the Arizona desert unintentionally tested the theory when their food ran short. Their health appeared to improve markedly, according to a number of measures.
The new study found "profound and sustained beneficial effects" in 18 people from the United States and Canada who had been eating very low calorie diets for three to 15 years, the researchers wrote in a paper being published in the April 27 issue of the Proceedings of the National Academy of Sciences. While far from proving the theory, the findings provide the strongest direct evidence yet in people, several experts said.
"It is a very important paper," Roy L. Walford, a professor emeritus at the UCLA School of Medicine and a leading proponent of the theory, said in an e-mail interview. "You may well be able to choose between [caloric restriction] and that double-bypass cardiac surgery you are not looking forward to."
'I'm a very disciplined person'
Several researchers cautioned that it was unclear whether the improvements were directly the result of caloric restriction, or simply caused by losing weight, eating more healthful diets or other beneficial behavior. In addition, the study was not able to assess whether the lower risk factors translate into longer life. Nevertheless, they said, the findings provided important encouragement to continue exploring the theory.
Holloszy and his colleagues conducted the study after stumbling across an online organization of about 1,000 adherents, called the Calorie Restriction Society.
One of the members, Dean Pomerleau, 39, a computer engineer from Gibsonia, Pa., cut his daily caloric intake from about 3,000 calories a day to about 1,900 more than four years ago. Pomerleau eats a highly regimented diet that consists of the same two meals daily of nothing but fruits, vegetables and nuts, with a couple of cups of non-sweetened herb tea for snacks.
"I'm a very disciplined person, and food has never been a critical, driving force in my life. So I've never found it as difficult as many may have," Pomerleau said. "For many it is difficult, especially in the beginning. But what you find is that once you get into it it's not a hardship at all. We actually consider it a preferable way to live."
On its Web site (www.calorierestriction.org), the Calorie Restriction Society offers advice for how to maintain equally low-calorie diets but with considerably more variety, including detailed recipes for fish and chicken dishes, a "Pastafree Veggie Pastalike Dish" and more appetizing items such as "Sherm's Bingeing Brownies," "Dean's Fruit and Veggie Smoothies" and "Sherm's Megamuffins."
"Creating highly nutritious low-calorie meals takes some practice," the site says. "Fortunately some of our members have been practicing for a long time and have published their creations to share with you."
Lower 'bad' cholesterol, lower blood pressure
Overall, Pomerleau and the other study subjects had reduced their intake to between 1,100 and 1,950 calories a day for an average of six years. Holloszy conducted a battery of tests on them and compared the results with the participants' earlier medical records, and with results from a similar group of 18 adults who ate a typical Western diet of between about 1,975 and 3,550 calories a day.
Those on low-calorie diets had much lower levels of "bad" cholesterol, much higher levels of "good" cholesterol, lower levels of triglycerides and very low blood pressure. Tests of their arteries showed they looked more like those of children than middle-age adults.
In addition, their blood sugar levels were very low and their body's response to insulin was extremely high, indicating they were at very low risk for diabetes.
At the same time, they had very low blood levels of a substance known as c-reactive protein (CRP), which is believed to be a marker for inflammation in the body. Many researchers believe low CRP levels are linked to a lower risk for a host of ailments, including heart disease, cancer and Alzheimer's.
"It's very clear from these findings that calorie restriction has a powerful protective effect against diseases associated with aging," Holloszy said. "We don't know how long each individual actually will end up living, but they certainly have a much longer life expectancy on average because they're most likely not going to die from a heart attack, stroke or diabetes."
But at a time when the number of Americans who are overweight and obese is soaring despite intensive public health campaigns to get people not to overeat, the idea that large numbers would be willing or able to go even further is daunting, many experts said. If scientists prove the theory, however, they might be able to develop new drugs that harness the biological mechanisms at work or new, safer appetite suppressants that may help more people eat less, experts said.
"If the drug companies can come up with a safe way to control appetite, which is being aggressively investigated, then in that case these kinds of findings may suddenly have profound public health implications," said Richard Weindruch of the University of Wisconsin Medical School at Madison, who studies caloric restriction.
The National Institutes of Health has launched pilot studies to determine whether it is practical to get healthy middle-age Americans to eat very low-calorie diets.
"If in fact it's shown to have beneficial effects, that might give more incentive to lower caloric intakes," said Evan Hadley, an associate director at the National Institute on Aging. "One of the things we're trying to find out is whether lower caloric intake may do things that exercise doesn't do."
