Jesus thought fasting was good for the soul. So do Jews, who fast on Yom Kippur; Muslims, who fast by day during Ramadan; and Catholics, who fast on Ash Wednesday and Good Friday.
Ghandi fasted for political reasons – to liberate India in the 1920s and 1930s. IRA member Bobby Sands did, too, fasting in prison in 1981 – he died after 66 days – to protest being denied prisoner-of-war status.
And this month, Chuck Purcell, 52, a Virginia engineer at the Department of Energy, joined their ranks, taking nothing but water for 12 days. But like many other overfed folks in this land of plenty, he fasted not for spiritual or political reasons but for health: to try to lower his blood pressure and banish an itchy skin problem.
Fasting – the voluntary abstinence from food – is probably as old as the urge for self-control and spiritual purification, and whether it achieves those ends is a subjective judgment.
But proponents of fasting often claim it has medical benefits, too, like “detoxification,” healing auto-immune diseases, losing weight, and restoring bodily harmony. Does it?
With some important qualifiers, the mainstream answer is no.
“Fasting is not good for you medically,” says Dr. George Blackburn, a Harvard nutritionist. “There’s no such thing as a therapeutic fast.”
Fasting “sounds like it would cleanse you, but there’s really no science to it,” adds Elizabeth Ward, a registered dietician and spokeswoman for the American Dietetic Association.
“Fasting is basically bad news,” agrees physiologist Susan Roberts, head of the energy metabolism lab at Tufts University’s human nutrition research center.
The reason they are so emphatic is this: When you stop eating completely, even if you take in plenty of water, you start breaking down protein – muscles – almost immediately.
For the first 12 to 16 hours of total abstinence, there’s enough glycogen – stored sugar – in the liver to keep your brain, the chief consumer of energy, happy.
But during the next day and a half, the body makes glucose from amino acids stolen from muscle protein. At first, you lose protein from inside a muscle cell, which can be replaced. But soon, whole cells disappear, and they’re hard to replace.
After two days of abstinence, the body does begin burning fat for energy, but it takes 21 days before you adapt sufficiently to starvation that you stop losing protein. Granted, the body’s ability to switch from burning glucose to burning fat is a wonderful evolutionary adaptation that has undoubtedly aided survival when starvation, not obesity, was the chief threat.
But burning fat also produces ketone bodies, snippets of fatty acids, that can dehydrate you, give you bad breath and, some nutritionists think, have toxic metabolic effects.
It’s true you can live this way for more than 40 days, perhaps even 100, if you’re healthy and drink water. But ultimately, of course, if you don’t eat, you die.
That said, there may be some medical benefits to fasting, particularly modified fasting, for carefully selected patients.
There’s considerable evidence, for instance, that severe diabetes can be brought under control quickly on a modified fast in which the patient eats nothing but 9 to 12 ounces a day of protein (meat, fish or fowl), plus electrolyte supplements, and bicarbonate of soda, says Blackburn. Eating protein slows the wasting of muscle; and with no intake of carbohydrates, blood sugar stabilizes.
Modified fasting can also lower blood pressure. During his fast, Purcell’s pressure fell from 140 over 90 to 108 over 78.
Scandinavian data suggests that fasting also helps people with arthritis, says Dr. Joel Fuhrman, a guru in Belle Mead, N.J., who has overseen the fasts of thousands of patients, including Purcell, who paid $ 1,200 to live in Furhman’s home during his fast.
When no food is taken in, Furhman believes, the body’s inflammatory response to foreign substances may decrease, thus allowing the hyperactive immune system – the hallmark of auto-immune diseases like rheumatoid arthritis – to calm down.
Alternative medicine specialists, like Dr. Jay Glaser, medical director of the Maharishi Ayurveda Medical Center in Lancaster, believe modified fasting – a liquid diet (fruit and vegetable juices, broth and herb tea) one day a week – can also reset the “food-seeking thermostat” and “lighten the body.”
In ayurvedic medicine, which originated in ancient India, fasting is believed to increase “digestive fire” (agni), get rid of metabolic clutter (ama), and offset heaviness (kapha).
Western medicine scoffs at the notion that fasting is necessary to “detoxify” the body.
“People think there’s a whole bunch of junk floating around in their bodies,” says dietician Ward. That’s nonsense – the liver, kidneys, colon and sweat glands do a great job of waste control. If you want to do something extra, eat more fiber.
You’re also fooling yourself if you think fasting will jump start a weight-loss program. Fasting is a lousy way to lose weight – the metabolism slows down so much that when you start eating again, you’ll gain weight faster than before.
It is true that fasting may give you a sense of control, says New York psychologist Sandra Haber, who specializes in eating disorders. Many people complain that they can’t control their spouse, their work, their kids, or their feelings, and that the only thing they do have control over is food intake, she says.
But if control is the issue, “you’re better off going after it directly,” she says. In other words, “Let’s talk.”
It is also true that fasting may give you an emotional high. Part of this may come from the stress of early starvation, which triggers adrenalin. And part may be a sense of “doing penance” and being “spiritually clean,” says Larry Lindner, executive editor of the Tufts University Health & Nutrition Letter.
But fasting can also make you grumpy and weak. Reached on Day 10 of his fast, Purcell was in good spirits, but felt weak climbing stairs and admitted that Day 3, when he had dry heaves, had been “very difficult.” He was pleasantly surprised, though, that hunger was not a problem.
If, despite the shaky medical justification, you still want to fast for spiritual reasons, that’s fine, nutritionists say. Just don’t do it too often and don’t do it in two-day bursts, which would maximize muscle loss. The best bet is to keep fasts short – 12 hours – and to load up on carbohydrates beforehand.
While starving, Jews studied hunger
Most of the research data on human starvation comes from heroic studies by Jewish doctors and nurses in the Warsaw Ghetto during the Nazi occupation of Poland in the early 1940s.
As they themselves suffered, 28 doctors and perhaps 200 nurses kept track as the Nazis tried to starve the 250,000 Jews in the ghetto. It is “the only scientific study in which most of the investigators died at the end,” says Dr. Ronenn Roubenoff, a Tufts nutritionist. “It is truly a testament to the human spirit.”
Though a child needs 1,000 calories a day, a woman 2,000 and a man, 3,000, the Nazis allowed so little food into the ghetto that people were living on 800 calories a day or less – usually from thin soups and crusts of bread.
Meticulously, the researchers documented the effects: the loss of growth in children, the slowing of the eye’s response to light, the disappearance of the thymus gland (a key part of the immune system), the inability of the immune system to produce a normal response to tuberculosis skin tests and, of course, the loss of body fat and muscle.
Although it is contrary to Jewish law, the doctors also did autopsies on 492 people who had no other cause for death than what the researchers called “hunger disease.” (Overall, during the three years the Jews were confined to the ghetto, 98,165 died, 18,320 of hunger disease.) The researchers also found death came quickly once people lost 40 percent of lean body mass.
The researchers smuggled hundreds of pages of data out to a non-Jewish doctor at the University of Warsaw who buried the data in his backyard until the war was over. In 1945, one of the surviving ghetto doctors dug it up and wrote an 80-page summary, but before he could analyze the data fully, he died.
His widow sent the summary, written in French, to the United Nations, where, “like any great bureaucracy, they filed it,” says Roubenoff. It was not until 1966 that a Polish history student stumbled upon it while looking through UN archives. He then contacted a Columbia University nutrition professor and together, they tracked down the primary data, analyzed it and published it in 1979.