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Doctors frown on fasting for health

ATLANTA -- Joslyn Chandler, 24, occasionally fasts.

"I do it for health, but I've also lost weight on it," says Chandler, a longtime vegan -- someone who eats no meat or dairy products.

Chandler, who works at the Life Grocery & Cafe health food store and restaurant in Marietta, Ga., practices the "raw foods lifestyle." The diet, she says, recommends fasting once a week.

"I just generally feel better on the raw foods lifestyle," she says.

Chandler started fasting before hearing of research published recently hinting that, if mice provide any clue, fasting every other day could help people tone their hearts, lower their blood pressure, improve their memories and maybe even live to be 100.

Slow down, though, before joining the fast track. Nutritionists and other experts warn that animal studies sometimes don't mean much, if anything, for people.

Chris Rosenbloom, a nutritionist at Georgia State University, frets that "fasting isn't normal or healthy" and could be harmful. "If you're fasting for religious reasons, fine, but in terms of fasting for long-term health, I'm not aware of benefits," says Rosenbloom.

"Animals on restrictive caloric diets may have longer life spans and fewer chronic diseases, but there aren't any studies to show the benefit with people, though some subscribe to the philosophy. Without food, we can become irritated, disoriented, fuzzy-headed. I wouldn't recommend it as a way to improve longevity or health or to lose weight."

Even if fasting makes people physically healthier, it also could addle them enough to step off a curb and get hit by a car.

"There are many weird and extreme approaches to dieting, but balance is necessary for a good diet," says Emory University nutritionist Nancy Anderson. "Our brains require blood sugar or glucose to function, and if deprived, one could assume it would impair mental abilities," she says.

"People would be much better off if they just would watch their calorie intake. Most studies on starvation and near-starvation indicate that that would weaken your immune system, even for simple diseases like colds."

But fasting might offer numerous benefits, reducing the risk of contracting everything from Alzheimer's disease to diabetes, if the mouse study pans out with people, says Dr. Mark Mattson, whose research was published this week in the Proceedings of the National Academy of Sciences.

Mattson and his colleagues at the National Institute on Aging, part of the federal National Institutes of Health, are now designing a similar experiment using humans.

"Would humans see the same long-term benefits? We think so, but don't know," Mattson says.

But mice are one thing, people another. In fact, we may be more like rats -- which also were tested in a separate study by the researchers, also led by Mattson.

Mattson found that mice deprived of food for a whole day gorged the next, consuming all the calories they'd been deprived of and more. The mice lived 30 percent to 40 percent longer than normal, but they didn't lose any weight.

In the similar study on rats, the bigger critters -- distant cousins of mice but different in many ways -- lived longer, healthier lives, just like the mice. But only the rats experienced the added benefit of weight loss.

What would happen to people remains to be seen. "We don't know if they'd lose weight like rats or just live longer and healthier like the mice and rats, or whether they'd benefit at all," Mattson says.

Art Seiden, 46, a chiropractor, has been thinking about fasting since he heard about Mattson's study. He's been fighting his own battle of the bulge for over a decade.

"Nothing else has worked -- not regular exercise, not cutting back," Seiden says. "I do fast on Yom Kippur, from sundown the day before to sundown the next day, and have done it all my life. But I don't lose weight. Maybe it takes more than just 24 hours. I weigh 230 and should be at 190."

Seiden, who walks for exercise and plays basketball, softball and baseball, realizes that his extra weight undermines his long-term health. And he wants to look trimmer.

He figures that if he can fast once a year for religious reasons, he could do it more often if his doctor gives him the OK.

But for now, such approval is unlikely, says Dr. Laurence Sperling, director of preventive cardiology at the Emory University School of Medicine. Doctors don't recommend fasting, and that won't change unless studies on humans produce the same results as the ones on rodents, says Sperling, who does find the study on mice "very interesting."

"Although this is provocative data, more investigation is needed before this would be a recommended form of dietary therapy," Sperling says.

Even for short periods, fasting can be dangerous for some people with diabetes or other existing medical problems, Sperling says.

"I would not recommend experimenting with this kind of [fasting] regimen before consulting with your physician," he says. "People already fast for religious reasons, but for shorter periods."

But "to compare mice and men would be difficult," he says.