Fasting is good for the soul, so they say, but it may also be good for the body, according to recent research.
New studies at the National Institute on Aging, the Longevity Institute at the University of Southern California, the UK's University of Manchester, Intermountain Heart Institute in Murray, Utah, and the University of Illinois suggest fasting may significantly reduce the risks of developing dementia, cancer, diabetes, and other diseases.
Findings from the studies were originally published in the New Scientist in November this year.
The Washington Post quotes Mark Mattson, a researcher at the National Institute of Aging, as saying:
"We know from animal models that if we start an intermittent fasting diet at what would be the equivalent of middle age in people, we can delay the onset of Alzheimer's and Parkinson's."
Researchers also found that a focus on calorie restriction alone can leave people vulnerable to infections and other biological issues, whereas responsible fasting didn't, the Post notes.
"The evidence is pretty strong that our ancestors did not eat three meals a day plus snacks," Mattson said. "Our genes are geared to being able to cope with periods of no food."
New Scientist reports that there are different types of fasting. The normal recommended daily intake for a woman is around 2,000 calories and 2,500 for a man. From that starting point, partial, full, and everything-in-between-fasting works back from those figures.
A fast is generally considered to start about 10 to 12 hours after a meal, which is when all the available glucose in the blood has been used up and will then convert glycogen in the liver and muscle cells into glucose to use for energy.
According to Valter Longo, director of the Longevity Institute at the University of Southern California, research showed that a 48-hour total fast slowed the growth of five of eight types of cancer in mice, with the the effect accelerating the more fasts the animals were given.
Reason for this, says Longo are that fasting changes the conditions under which the original cancer mutations arose.
New Scientist notes that research on mice with gliomas --- an aggressive form of cancer and the most typically diagnosed brain tumor in humans --- were more than twice as likely to survive a 28-day study if they took a 48-hour fast along with radiation therapy as opposed to those who didn't fast.
Michelle Harvie at the University of Manchester found that, in a study group of women predisposed to breast cancer, after six month,s the half that were put on a controlled calorific diet showed a reduction in blood insulin levels --- but the reduction was greater in the fasting group, said the Post.
For diabetes, there are encouraging results too. At the Intermountain Heart Institute in Murray, Utah, Benjamin Horne found that a monthly, 24-hour, water-only fast, raised levels of the human growth hormone which in turn triggered the breakdown of fat and reduced insulin levels.
People in the study group not only lost weight but also reduced their risk of developing diabetes and coronary heart disease. Similar benefits were discovered from alternate-day fasting at the University of Illinois.
Back at the National Institute of Aging, a 2007 study that put 10 overweight people with asthma on an alternate-day fast, resulted in an improvement in their asthma symptoms after a few weeks. And it gets better.
New Scientist reports that Mattson believes fasting is actually good for the brain."If you look at an animal that's gone without food for an entire day, it becomes more active," he said. "Fasting is a mild stressor that motivates the animal to increase activity in the brain."
In fact, Mattson's studies indicated that alternate-day fasting --- with one 600 calorie meal on the fast day --- can boost the production of a protein called brain-derived neurotrophic factor by 50 to 400 percent. This protein is crucial to the generation of new brain cells, memory and learning, and can protect brain cells from changes related to Alzheimer's and Parkinson's, said The Guardian.
Harvie notes there are risks. "We still don't know exactly who should be fasting," she said "how often or how many days a week."
It should also be noted that one one rat study found that even alternate-day fasting reduced the heart's ability to pump blood. The results of that particular study are published in the Journal of Cardiac Failure.
Does any of this make you want to try supervised, doctor approved fasting, or do you think going without that second piece of Christmas pudding did the trick?