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Taking a break from eating

New research looks at short-term fasting to boost healing and fight diseases such as Alzheimer's and cancer

By Karen Weintraub
Globe Correspondent / March 12, 2012
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Mark Mattson and Valter Longo eat only once a day during the week, going without any food 23 hours at a time. Wolfram Tetzlaff sits down to a meal only every other weekday. And James R. Mitchell has tried skipping food entirely for several days at a time, though he much prefers juice fasts.

Their wacky eating is not about weight loss. The four are studying the possible benefits of short-term fasting, and figure they should experience it themselves.

Their hypothesis: Since three square meals a day and regular snacks were not always available to our hunter-gatherer ancestors, the human body may have evolved to perform at its best with short-term feeding gaps. So sporadic food deprivation might have a positive effect on metabolism, giving a boost to such things as cancer treatment, Alzheimer’s prevention, and wound healing.

The research so far has been mostly in animals, so it is far too early to advocate fasting for people. But the idea is gaining attention: Findings were recently discussed at a meeting of the American Association for the Advancement of Science, a leading nonprofit scientific organization, and specialists not involved in the work say the theory makes sense.

The idea springs from the 80-year-old observation that rats, and more recently other animals, live longer when fed a well-balanced, near-starvation diet. Though this effect has never been shown conclusively in people, Mattson and others have been looking for less-drastic ways to trigger the probable benefits of caloric restriction.

“If someone’s looking for a diet for weight control, go somewhere else [than fasting],’’ said Dr. George L. Blackburn, chief of the Nutrition/Metabolism Laboratory, and director of the Center for the Study of Nutrition Medicine at Beth Israel Deaconess Medical Center. But he agrees that intermittent fasting might improve the body’s ability to process sugar, which would reduce the risk of diabetes and some cancers.

“It’s plausible,’’ he said. And skipping a few meals, even on a regular basis, isn’t dangerous, he said.

Brain cells become more active after not being fed, according to Mattson, a leader in the study of intermittent fasting and chief of the Laboratory of Neurosciences at the National Institute on Aging. “If you haven’t eaten for a while, you’d better be figuring out how to get food,’’ he said.

His research - still only on otherwise well-fed mice that don’t exercise much - suggests that short periods of low or no calories create a kind of productive stress in the brain. Cells that have not been fed in a while switch on a gene called BDNF, which plays a role in preventing Alzheimer’s and Huntington’s diseases, as well as mood disorders.

Mattson says he is fairly confident his research will translate to typical Americans, who eat too much and don’t exercise enough. He is not so sure that intermittent fasting will benefit people like him, who are naturally thin and driven to exercise.

Personally, he is willing to hedge his bets, given that his 90-year-old father has Alzheimer’s. Mattson eats only dinner on weekdays and indulges a bit more on weekends.

Normal, healthy cells are not harmed by such gaps in food supply, nutrition experts agree, but cancer cells might be weakened by it.

Administering chemotherapy when cancer cells are weakened by hunger makes the cells more vulnerable, said Longo, a professor of gerontology and biological science at the University of Southern California. He published a study earlier this year showing that evidence of cancer disappeared in up to 40 percent of the mice who fasted during treatment - while no mice who had chemo while eating regularly appeared cancer-free. He is now running two trials with a total of 60 cancer patients to see whether fasting is safe for them and whether any of the results seen in mice will carry over.

Cancer patients should definitely not try fasting on their own, Longo warns. Apple founder Steve Jobs, for example, might have done himself more harm than good by eating too little and relying too much on making dietary changes to address his pancreatic cancer, Longo and others have said.

Giving up too much food for too long during treatment can weaken patients and their immune systems, while eating at the wrong time could actually fuel the cancer, Longo said.

“This has to be timed very carefully and monitored,’’ he said.

Beyond cancer, Mitchell and Tetzlaff are pursuing the idea that being hungry might help with healing. In work with mice, Mitchell, an assistant professor of genetics and complex diseases at the Harvard School of Public Health, has found that short-term stress caused by lack of food seems to prevent the mice’s immune system from overreacting to surgery. “These animals come through surgery much better than the well-fed, happy, healthy-looking animals,’’ he said.

The big surprise in recent research, Mitchell said, is that it takes only about three days of going without solid food to trigger this helpful response - making it more likely that patients could follow it and that doctors would recommend it.

Tetzlaff, a professor in the neurosurgery department at the University of British Columbia, has found that rats fed only on alternating days after a spinal cord injury recover more mobility than those allowed to eat as much as they want.

Of course, with obesity rates skyrocketing, there are researchers who study this approach for weight loss, too. Michelle Harvie, a dietitian and researcher at the Genesis Prevention Center at University Hospital in South Manchester, England, said a study she did with 115 women suggests that periods of food restriction improve insulin levels. One of the questions she and other researchers have is whether people can stick long-term to diets like this. Or whether there are other ways to get the same results.

“We need to do more work, but I think it’s interesting,’’ Harvie said.

Because the goal of these short-term fasts is not to lose weight, Mattson and others say they don’t think it will lead to eating disorders. Several eating disorder specialists declined to comment, saying they didn’t know enough about intermittent fasting to speculate on what effect it might have on eating disorders.

Several researchers said they are hoping to find an alternative to fasting - perhaps in a pill, or through a special diet - that could achieve the same results without the deprivation. (Longo has a federal grant to study a product he is developing for cancer patients.)

Of course, in addition to the difficulty of sticking to a restricted diet, there is another downside to skipping meals: “Rumor has it I’m a bit grumpier - borderline aggressive in the afternoon,’’ Tetzlaff admits.

Karen Weintraub can be reached at

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