Researchers are finding evidence that periodic fasting is beneficial
"I've tried everything," says Maggie Bass, 52, who at 5 feet 1 inch tall topped out early this year at 197 pounds. "I can't stick to a diet. After a few weeks I start to - I guess the word is cheat." Over the years, Bass says, she has lost the same 14 pounds over and over and "put it right back on again." This time, by picking an approach that has long been a no-no - skipping meals - she has hurdled that 14-pound barrier and is still headed down.
Bass, of Peterborough, England, swears by a technique known as intermittent fasting that has become a craze in the U.K. thanks to a couple of new books there: "The FastDiet" by doctor and science journalist Michael Mosley and co-author Mimi Spencer, which hit American bookstores in February and was featured in a companion documentary on PBS, and "The 2-Day Diet" by British dietician Michelle Harvie and professor of medical oncology Tony Howell, which arrived here in June. Two days a week, Bass skips breakfast and lunch and has salmon with roasted vegetables for dinner. The other five days, she's free to eat without weighing the merits of every bite of food. "I'm eating less, and I'm eating healthier," she says. "I'm not constantly thinking about food."
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To be sure, the global obesity epidemic is stark proof that knowing the basics of good nutrition and obsessively accounting for every calorie don't do the job for 21st-century humans. Now, a few researchers are beginning to suggest that a dose of prehistoric feast and famine might be the better ticket to both weight loss and improved resistance to disease. Intermittent fasting requires spending two, perhaps three, days a week eating about a quarter of the calories of a normal diet: 500 for women, instead of the usual 2,000, and 600 for men instead of 2,500. The other days, you might be able to forget calorie counting, within reason.
Mosley, 56, is a year into intermittent fasting himself, and has dropped from 187 pounds to his goal weight of 166 pounds as his cholesterol and blood glucose levels have gone from troublesome to normal. And his tastes have changed. "I eat more vegetables and have less of an urge for chocolate-y things," he says. Now he fasts one day a week to maintain his weight.
Small studies by Harvie and Howell and others have suggested that regular intermittent fasting is effective at promoting weight loss and at lowering the body's resistance to insulin, important to avoiding diabetes. But there's still a lot of research to be done on people. Some recent research has linked skipping breakfast, at least, to elevated heart risks and insulin resistance (though proponents argue that the beneficial effects can take weeks to kick in). "We'll need huge, long-term studies before we can say that this is the way to go," says Kristin Kirkpatrick, a registered dietician and wellness manager for the Cleveland Clinic's Wellness Institute. In the meantime, experts are finding a case for the practice in evolutionary science, observations of modern periods of food scarcity and animal studies. Early man, the theory goes, had to eat when he could and, in frequent times of scarcity, went without while engaging his brain on finding a food supply. That ancient genome has remained pretty much unchanged. The stock market crash of 1929 hinted at the silver lining of having fewer calories available. In 2009, researchers from the University of Michigan who looked at health outcomes during times of plenty and lean years found that life expectancy rose to 63 in 1933 from 57 in 1929. Those who fast for religious reasons - Hindus, Buddhists, Muslims and Seventh-Day Adventists, for example - also provide evidence that going without periodically improves cardiovascular health markers and the body's sensitivity to insulin.
And many clues come from animal studies. Mark Mattson, chief of the Laboratory of Neurosciences at the National Institute on Aging in Baltimore and a professor of neuroscience at Johns Hopkins, has found, through years of longevity research, that rats and mice fed only every other day benefit in health measures like blood pressure and glucose and insulin levels. And their brains seem protected against diseases like Alzheimer's. Mattson, who began fasting himself 25 years ago, skips breakfast and lunch three or four days a week, then eats a reasonable dinner. "I go 16 to 18 hours without food," he says. "From a scientific standpoint, 10 to 12 hours after eating, I'll have completely used up what I've eaten. Then you start burning fat, and a lot of good things start happening throughout the body and brain."
When people go without food for, say, 16 hours or more, nerve cells in the brain get more active, says Mattson. He has studied the effect of that on a protein called BDNF (brain derived neurotropic factor), which plays a part in learning and memory and has an antidepressant effect. When nerve cells are more active, levels of BDNF rise, fueling the theory that fasting might delay dementia. And besides improving the glucose and insulin picture, fasting can lower levels of insulin-like growth factor, or IGF-1, a protein that encourages rapid division of cells. In adults, too much IGF-1 appears to lead to accelerated aging and cancer, says Mosley.
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Nutrition researchers have wondered for decades if drastically cutting calorie intake overall might extend life, as it does in animals. That has yet to be proven, though the practice clearly affects markers of aging. Luigi Fontana, a professor of medicine at Washington University in St. Louis, has studied members of the Calorie Restriction Society, who eat about 30 percent fewer calories than normal in an effort to live longer. A 2007 review of his and other studies shows that after an average of six and a half years on the restricted diet, members had greatly reduced their risk factors for heart disease and diabetes. Eating much less every day, Fontana has found, lowers inflammation and results in a more elastic left ventricle - a "younger" heart - and helps reduce the incidence of many cancers associated with obesity.
But the problem with consistently low-calorie diets is that most people can't stand the ongoing deprivation. Fontana is launching a pilot study of 40 people to see if 500 or 600 calories two to three days a week can mimic the effects of a very-low-calorie daily diet. Mattson is also preparing a small study to see if intermittent fasting affects early markers for cognitive decline among obese insulin-resistant people aged 55 to 70. Meanwhile, especially in light of the research supporting breakfast, it's wise to check with your doctor before trying fasting.
The most controversial idea to arise in the recent media storm about the practice is that people can eat whatever they want on nonfasting days. Experts warn that low-calorie days should be packed with nutrients, and that fasters should maintain a proper balance on normal days, too.
Maggie Bass's total cholesterol is still high, but has dropped from about 266 to 243 since she changed her eating pattern. The weight has come off slowly - about a pound a week. Can she keep it up? Time will tell, but she has stuck with fasting for longer than any diet she's tried before.
- Disease & Medical Conditions
- intermittent fasting
- Michael Mosley