Something about the way Americans eat isn’t working – and hasn’t been for a long time.
The number of obese Americans is now greater than the number who are merely overweight, according to government figures released last month. It’s as if once we taste food, we can’t stop until we’ve gorged ourselves.
But rather than battling temptation in grocery stores, restaurants and their own kitchens, some people simply don’t eat – at least not at certain times of the day, or specific days of the week.
Called intermittent fasting, this rather stark approach to weight control appears to be supported by science, not to mention various religious and cultural practices around the globe.
The practice is a way to become more circumspect about food, its adherents say. But it also seems to yield the benefits of calorie restriction, which may ultimately reduce the risk of some diseases and even extend life.
Some fasters ultimately switch from regular, if comparatively rare, periods of hunger to permanent deprivation, limiting calories all the time.
For years, Dennis Brooks had struggled to keep his weight down. After retiring from the Army, he was in an auto accident and gained even more.
To address his frustration, Brooks, 60, began skipping breakfast. Then, pleased with his modest weight loss, he began forgoing lunch as well.
Now he eats on alternate days (soup, salad, fish or lean meat, vegetables, nuts and occasional desserts) and only drinks water on the other days.
“I have found that on the fasting days if I eat anything it triggers more eating. But if I don’t eat anything, I don’t have an appetite,” says Brooks, who recently published a book about his experience titled “The Skip-a-Day Diet System.”
Brooks, who lives in Hawaii, has lost 50 pounds, gained energy and says his blood pressure and cholesterol levels have improved markedly.
“There is something kind of magical about starvation,” says Dr. Marc Hellerstein, a professor of endocrinology, metabolism and nutrition at the University of California at Berkeley who studies fasting.
“In normal health subjects, moderate fasting – maybe one day a week or cutting back on calories a couple of days a week – will have health benefits for most anybody,” adds Mark P. Mattson, chief of the laboratory of neurosciences at the National Institute on Aging and a leading researcher on the effects of calorie restriction.
Not all nutrition professionals see the merits of fasting. Some think of it as a recipe for disaster, setting up a person for binge eating and metabolic confusion.
Ruth Frechman, a registered dietitian in Burbank, Calif., and spokeswoman for the American Dietetic Association, says she frequently sees such extreme strategies backfire.
“You’re hungry, fatigued, irritable,” she says. “Fasting is not very comfortable. People try to cut back one day, and the next day they’re starving and they overeat.”
Researchers who study fasting and caloric restriction, however, say the body’s hunger cycle ultimately adjusts.
From a biological standpoint, they say, fasting can be helpful whether someone is overweight or normal weight.
“We’re brilliant at this,” Hellerstein says, referring to humans’ physical reaction to not eating. “We’re not good at responding to too many calories, but we’re very good at responding to fasting. Fasting, in itself, is not an unhealthy process.”
During fasting, almost every system in the body is “turned down,” Hellerstein says. The body changes how it uses fuel. Certain hormone levels fall. Growth stops. Reproduction becomes impossible.
“By the end of three weeks of fasting, you are a completely different metabolic creature,” he says.
“It affects many, many processes – but in a somewhat predictable way that takes you toward disease prevention.”
Put simply, intermittent fasting appears to offer the same advantages as long-term calorie restriction – defined as eating at regular times, but consuming 25 percent to 30 percent fewer calories than what is recommended for that person based on age, size and gender.
People who eat this way tend to do so by filling up on nutrient-dense but low-calorie foods. They get all the protein, fiber, vitamins and minerals the body absolutely needs – and very little else.
Dan Golden, 46, a Los Angeles-area librarian, began practicing intermittent fasting almost 15 years ago.
For many years, he ate a large meal four days a week and had fluids on the other days. He eventually became too fatigued on the days he was fasting.
Now he eats about 1,800 to 2,000 calories a day on a diet consisting mostly of fruits, vegetables, rice and beans.
“I found I no longer have an interest in sugary foods,” says Golden. “It’s not because I’m snooty and won’t eat it. I just don’t have an interest in it.”
Kathleen Flinn fasted one day each week from 1999 to 2003 while working as a restaurant reviewer in Europe. But after she enrolled in cooking school at Le Cordon Bleu in Paris, she stopped fasting and gained 30 pounds.
Now a food writer in Seattle, she recently resumed a once-a-week fast, skipping dinner on Mondays and consuming only fruit and vegetable juice and broth on Tuesdays.
“I find that, even after one day, my taste is more acute,” says Flinn, 41. “It makes me more aware of what I’m eating. You learn to understand when you’re really hungry and when you’re just thirsty or tired.”
Flinn admits she is hungry on fasting days and keeps mentally busy to avoid thinking about food. On Wednesday mornings, she dips a cautious toe in the kitchen.
“I try not to gorge myself,” she says. “I think where people make the biggest mistake is when they come off the fast. They are incredibly hungry. It’s the part of the fast that takes the most discipline.”
Calorie restriction shouldn’t result in excessive thinness, experts say. It’s not appropriate for children or adolescents, who are still growing, or people with serious illnesses. And those with diabetes or heart disease should adopt the diet only with a doctor’s approval.
People who use intermittent fasting hoping for quick weight loss may have disappointing results, experts add.
The body’s general weight is established through genes and chronic eating patterns, says Dr. Marc Montminy, a researcher at the Salk Institute for Biological Studies who studies fasting.
After weight loss, he says, “your body will very quickly try to re-establish your set point. If you lose weight more gradually, maybe this gauge can be reset.”
But the other health benefits of intermittent fasting are well-established.
Researchers aren’t sure why the body apparently benefits from a state of mini-starvation. One theory is that the process produces just enough stress in cells to be good.
“What our evidence suggests is that nerve cells in animals that are on dietary energy restriction are under mild stress,” Mattson says, which “stimulates the production of proteins that protect the neurons against more severe stress.”
What scientists do know is that occasionally going without food or reducing calories daily makes the body more sensitive to insulin, which helps maintain normal blood sugar levels. And animal studies suggest calorie restriction may reduce the risk of cancer by slowing the growth of abnormal cells.
Intermittent fasting and calorie restriction also have been shown in animals to reduce cognitive decline in diseases such as Alzheimer’s disease and Parkinson’s disease, Mattson says.
Researchers caution that not many studies have examined humans who are practicing intermittent fasting or caloric restriction. But the little evidence that exists is favorable.
A study at the Salk Institute in San Diego, published recently in the Proceedings of the National Academy of Sciences, found that reducing calories 30 percent per day increased the memory function of elderly men and women.
University of Utah scientists looked at health data from members of the Church of Jesus Christ of Latter-day Saints, who have lower rates of heart disease than most Americans. Mormons typically don’t smoke or drink alcohol, and some abstain from food on the first Sunday of every month.
After controlling for several factors that protect against heart disease, the researchers found that only fasting made a significant difference in lowering the risk of heart disease, according to the study published in October’s American Journal of Cardiology.
Among 448 people surveyed, intermittent fasting was associated with a more than 40 percent reduction in heart disease risk. Fasting also was linked to a lower incidence of diabetes.
Another study, published in 2007 in the journal Free Radical Biology & Medicine, showed that asthma patients who fasted had fewer symptoms, better airway function and a decrease in the markers of inflammation in the blood.
The National Institutes of Health is supporting calorie-restriction research at three medical centers.
At one study site, Washington University in St. Louis, Dr. Luigi Fontana is following the largest group to date of people who practice caloric restriction or intermittent fasting. So far his research shows that such people are not malnourished and have excellent cardiovascular health.
“Eating less is important, because 65 percent of the American population is overweight,” Fontana says. “But another question is: If you are already lean, should you change your diet to improve your health and possibly extend your life span?”
That ultimately may be the strongest selling point of a reduced-calorie lifestyle.
“It does demand more than some other diets,” says Joseph Cordell, 50, a St. Louis lawyer who limits his intake to 1,800 to 1,900 calories a day.
“But surely the payoff is dramatically better than anything else. I feel so much better and have more energy. And there is this prospect of living so much longer than you otherwise would.”
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