March 17, 2005
Every Other Day Fasting May Reduce Cancer Risk

Every other day fasting seems to provide mice with much of the known health benefits that calorie restriction diets are known to provide.

An apple a day keeps the doctor away, but could eating an apple every other day be better?

A new study by researchers at the University of California, Berkeley, raises such a possibility. It shows that healthy mice given only 5 percent fewer calories than mice allowed to eat freely experienced a significant reduction in cell proliferation in several tissues, considered an indicator for cancer risk. The key was that the mice eating 5 percent fewer calories were fed intermittently, or three days a week.

What is encouraging about the findings is that the reduction in cell proliferation from that intermittent feeding regimen was only slightly less than that of a more severe 33 percent reduction in calories. Until now, scientists have been certain only of a link between a more substantial calorie reduction and a reduction in the rate of cell proliferation.

The results of the study are scheduled to appear in the May 2005 issue of the American Journal of Physiology-Endocrinology and Metabolism, but are now available online.

"Cell proliferation is really the key to the modern epidemic of cancer," said Marc Hellerstein, professor of human nutrition in the Department of Nutritional Sciences and Toxicology at UC Berkeley's College of Natural Resources. Hellerstein is principal investigator of the study.

Cancer is essentially the uncontrolled division of cells, and its development typically requires the presence of multiple mutations. "Normally, a cell will try to fix any damage that has occurred to its DNA," said Hellerstein, "But, if it divides before it has a chance to fix the damage, then that damage becomes memorialized as a mutation in the offspring cells. Slowing down the rate of cell proliferation essentially buys time for the cells to repair genetic damage."

Cell proliferation contributes to carcinogenesis in a number of other ways, as well, collectively termed "cancer promotion."

Studies over the past 70 years have established that substantial calorie reduction - up to 50 percent in some studies - not only can reduce the rate of cell proliferation, it can extend the maximum life span of a variety of organisms, including rats, flies, worms and yeast. The results can be dramatic, with 30 to 70 percent increases in life span reported in the studies.

"Significant caloric restriction is the one and only thing that has been scientifically proven to extend life span," said Hellerstein, who has a joint appointment at UC San Francisco. He noted that while exercise and good nutrition can prevent premature death by disease, they have not been shown to extend a maximum life span.

Cutting calories has also been shown to reduce the development of cancer, enhance insulin sensitivity and lower the risk of heart disease.

The 5% reduction in calories used for mice translates into about 100 calories per day for humans. Many obese people overeat by about that amount and have little luck dieting to avoid those extra 100 calories. This brings into question the practicality of implementing this research in human diets.

Can some of the benefits of calorie restriction really be achieved by fasting every other day? To prove that this experiment would need to be run on mice and rats for years in order to find out whether this regimen increases their life expectancies and if so by how much.

Another question: Would one derive more benefit from even longer periods of fasting and eating? A week on and a week off perhaps? Or just 2 days fasting alternated with 2 days eating?

The researchers conducted several trials with a control group of mice that ate "ad lib," or freely. They compared the control group with mice that ate 5 percent fewer calories but were fed three times a week with mice that were given 33 percent fewer calories. Trial periods ranged from two weeks to three months.

As expected, the researchers found that mice on the 33 percent reduced calorie diet exhibited significantly decreased proliferation rates for skin, breast and T (lymphocyte) cells. The greatest effect was seen after one month on the regimen, when proliferation of skin cells registered only 61 percent of that for mice fed freely.

The surprising finding came with the results of the more modest 5 percent reduced calorie diet that was fed intermittently. Mice in this group had skin cell division rates that were 81 percent of those for mice fed freely.

Fasting every other day may decrease the chances of breast cancer the most. But I can not imagine many women being willing to fast every other day for weeks, months, and years on end.

In all cases, division rates for breast cells were reduced the most. Mice with the lowest calorie diet had breast cell proliferation results that were only 11 percent of those for the control group mice, and mice fed intermittently had results that were 37 percent of those for the control group.

The researchers said this may be partly related to the reduction in estrogen, which stimulates breast cell division. Tests revealed that the estrus cycle stopped for mice on the lowest calorie diet. The mice fed intermittently, on the other hand, continued to cycle regularly.

Results of the refeeding trials indicated that any weight lost during the calorie restriction period was regained once a normal feeding pattern was resumed.

Every other day fasting was tried on a small pilot study of humans.

A recent pilot study of 16 non-obese adults by researchers at the Pennington Biomedical Research Center in Louisiana found that eating only every other day was feasible when the participants successfully followed an alternate-day fasting regimen for three weeks. However, the people also reported feeling hungry and irritable on their fasting days.

The authors of the pilot study said that adding a small meal, fulfilling no more than 20 percent of the day's caloric needs, might just take the edge off and make the feeding pattern more palatable.

Would even shorter fasting periods provide any benefit? It would be interesting to see if any benefit could be derived by eating very day but having at least 12 hour stretches every day when no food is consumed. That might be more achievable. Don't eat before bedtime and then entirely skip breakfast and make lunch be the first meal of the day.

Even if intermittent fasting is eventually shown to deliver real human health benefits (and I expect it will) few people are going to be up for fasting every other day. Though perhaps more people could manage to do intermittent fasting than can manage to stay on a calorie restriction diet.

However, once safe appetite suppressant drugs are developed fasting could become a lot easier and may become popular as a method to slow aging and lower the risk of degenerative diseases. Appetite suppressants that could work for differing lengths of time would be handy. One could take an appetite suppressant for 12 hours or 24 hours depending on your fasting regime.

Another approach that may eventualy obviate the need for fasting is a class of drugs called calorie restriction mimetics. The idea behind calorie restriction mimetics (which are the subject of active research in a number of labs) is that they'll fool your metabolism into thinking you haven't eaten. Then your cells would throw themselves into the same state they go into when they are not getting as much calories. Appetite suppressants would remain useful for anyone who is overweight. But the benefit of fasting would be delivered by a separate calorie restriction mimetic drug.

Update: A previous study found that rodents genetically engineered to have less fat in fat cells lived longer without calorie restriction. This is not surprising because fat cells appear to excrete pro-inflammatory compounds. In fact. Rudolph Liebel of Columbia University says adipose fat cells excrete at least 25 hormones and other signalling compounds including adiponectin and resistin. The fatter you get the bigger the problem you'll have with accumulated damage from chronic inflammation. If we can develop treatments that prevent fat cells from converting excess calories into fat then we may be able to get many of the benefits of calorie restriction.

Also, see my previous post which reports that rodents which were made to skip meals had lower blood insulin and their brains were more resistant to damage from neurotoxins. Being skinny is good. Skipping meals is good too.

Share |      Randall Parker, 2005 March 17 02:05 PM  Aging Diet Cancer Studies

SpakKadi said at March 17, 2005 4:28 PM:

I regularly go without breakfast. In fact, I never ate breakfast until I started working. I only ate breakfast then because lunch could often be as late as 1 pm. It would be interesting to know if that means I'm at a reduced risk for cancer. However, wouldn't this mean that anorexic's have an incredibly low risk of cancer?

I have also heard that skipping meals occasionally can reduce the risk of diabetes (can't remember where I head that, though).

Alternative Energy Blog said at March 17, 2005 6:48 PM:

The effects of fasting for shorter periods of time could relatively easily be studied on Muslims who fast (no food or water) during daylight hours for around a month a year. Advantages would include a large study group and motivated test subjects.

michael vassar said at March 18, 2005 12:28 AM:

Anarexics who recieve adequate nutrition almost certainly have almost no risk for most types of cancer. I don't think skiping breakfast is good for much. There should be systematic research in humans and animals on varied fasting regimes to discover health effects. The expected utility per dollar is almost unmatched.

Jay Fox said at March 18, 2005 10:21 AM:

Well, Randall brought up the interesting point in his commentary about whether every other day fasting would be needed, or every other week, etc. The metabolism rates do beg this question. Certain small shrews will die if they don't eat for a whole day, or perhaps even 12-16 hours. Mice lives quite a bit longer, but are bigger, have a slower metabolism, and live 2-3 times longer.

Humans live another 20-30 times longer still, with an even more reduced metabolism (per kilogram, or gram, as the case may be). So I wouldn't be surprised if every other week fasting is really the correct equivalent we should be talking about. Which seems unhealthy, given the studies on essential amino acids and the effects of restricting them for even a couple days (while maintaining a normal caloric intake, so the study isn't completely relevant, since people fast for weeks all the time and don't show nearly the degree of health problems; nonetheless, caution is very warranted...).

So when all's said and done, I wouldn't go beyond 2 days on, 2 days off without further study in larger mammals (dogs, sheep, monkeys...)

Raina said at March 18, 2005 11:46 AM:

My parents have been doing this diet for a while that involves eating very little (juice/soup) one day, and normally the next. After a while, they stopped feeling as hungry on the low cal day, and even on the regular day. This seems to support the reduction in insulin that the other study found, so it seems possible that the reduced risk of cancer effects on mice would carry over the same as well, despite the differences in size and metabolism. My husband and I started doing the same thing a few weeks ago, and we're already feeling the effects of reduced hunger.

rjschwarz said at March 18, 2005 12:12 PM:

Fasting every other day is particularly cruel. I fasted for 3 days onces, the hunger pangs shut off after the first day so the second and third were easier. By fasting every other day you'd go through the worst pangs every time.

Oh, and on the third day I felt unfit to drive. I don't know if that was psychological or not but either way that would be something to consider on every other week fasting.

Patrick said at March 20, 2005 2:25 PM:

I've always wondered about the baseline in these studies. The control group is "Mice who eat as much as they want" but is this comparable to a human of what we now consider "healthy weight" or is a better comparison to a human who "eats as much as they want" which means the Homer Simpsons of this world?

If so, then most "healthy adults" are already on a calorie restricted diet, at least compared to an obese person who lives the lifestyle of a caged mouse who eats all day.

Futhermore, wouldn't a good control group be the traditional catholic lifestyle of fasting every friday except for fish?

michael vassar said at March 20, 2005 8:45 PM:

Actually, while the baseline may be a problematic point for comparison, it is worth noting that the metabolic changes associated with these studies (lower body temperature, infertility, lower activity level) don't occur in typical humans who refrain from gluttony in an everyday sense.

Patrick said at March 21, 2005 6:09 PM:

Good point Michael,

Though it would be hard to convince someone that something that makes them sterile and with less energy (lower activity) is actually good for them.

michael vassar said at March 22, 2005 6:48 AM:

Lower activity != lower energy. They sleep less and get sick less often.

David Nishimura said at March 23, 2005 6:34 PM:

This feeds into (sorry) the question of why the French eat such rich food yet maintain such good overall health. The answer that has been emerging is puericulture: an originally state-directed program of rearing children to eat sparingly at regular meal times and not in between. Fasting makes perfect sense in terms of our evolutionary history, and this is yet another piece of evidence. More info here.

a muslim said at May 24, 2005 10:34 AM:

In Islam the Prophet said the best method of fasting is to fast every other day. That was the method of Dawud (David).I guess Islam has more to it than most people would like to say.

Rev. Thomas S. Painter (R-FL) said at August 23, 2005 2:28 PM:

...excellent post.

Fasting and prayer surely do cast out demons.

I'd modify the timing and diet content though.
Here's an appetizer:

Doug said at December 17, 2005 8:36 AM:

"Would even shorter fasting periods provide any benefit? It would be interesting to see if any benefit could be derived by eating very day but having at least 12 hour stretches every day when no food is consumed. That might be more achievable. Don't eat before bedtime and then entirely skip breakfast and make lunch be the first meal of the day."

Arthur De Vany covers this topic in his weblog; his own practice is to maintain a 15-hour fasting interval overnight and to pick one day per week, randomly, on which to eat sparingly while remaining moderately active.

richard boyle said at December 26, 2005 2:02 PM:

i am 51 and over the years as my matabolism has slowed down i have made changes in my eating habits , first i cut out my 10am donut, then went breakfast except for coffee and tea combined , then went lunch , and was doing very well just eating dinner . when i retired 2 months ago and my activity slowed down ,i have gained 5lbs.So starting last week i switched to eating every other day . i am so used to fasting that skipping a day is not a problem. my weight moves about 3lbs. between eating and not 175,172, i can already tell this will be successful , and allows me to choose between maintaining or losing weight.

richard said at July 11, 2006 12:04 PM:

i have been eating every other day for 8 months now . i just eat one meal on my eating day so there is about 44 hours between meals . i have no loss of energy or headaches . of course i must be ever viligant , so as to not fall off the wagon . i think it would be very hard to return to eating normal .i am dropping about 1 pound every 2 months. so i am still about 155 at 5'8''.

Abdullah Sheikh said at March 3, 2008 2:15 AM:

Salam, WOW! MashaALLAH!
SUPREME in Wisdom is ALLAH (SWT) who guided His Prophet Muhammad (May ALLAH's Mercy and Peace be upon him) to explain to us that the best way of fasting was to fast every alternate day (just like the fasting of Prophet David, May ALLAH's Mercy and Peace be upon him).
This is not the only saying of the Prophet (PBUH) to which modern science has testified. Infact there is not a single verse of the Qura'an or a single sahih (historically validated) saying of the Prophet (PBUH) which science can object to on grounds of PROVEN scientific facts. I say this proves something!

Isabelle said at May 27, 2008 7:51 PM:

I am going to start eating 4 times a week.

Richard said at December 3, 2008 1:36 PM:

I have been eating every other day for three years now.It is very good at keeping you healthy and your weight under control.I am still at 155 lbs.and now eat snacks on my eating day.So having something at 10-12-2-4-6-8-10 during the day.

Gilbert said at July 24, 2010 12:09 AM:

I've been experimenting with water fasting and very low carb/calorie fasting for the last 2 months, and have lost about 16.5 pounds + about 4 inches off my waist. The longest I went was 4 days straight without food, and started to feel "off" - I couldn't sleep (fasting raises cortisol), my heart beat harder, and I felt overly alert. But I think 1 or 2 days a week of fasting could be good for almost anyone.

If you do a every other day fast, your hunger pangs don't return the day of the fast. This is most likely because of the stabilization of blood sugar and insulin. There's a misconception that as soon as people who are fasting stop their fast, they binge. Well for most normal people, high carbs and high sugar foods after a fast wreck havoc on their digestive system, so binging is kind of out of the question on a every other day fast diet.

Just my 2 cents and honest observations.

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