Thursday, November 9, 2017
Monday, August 20, 2012
Horizon Eat, Fast and Live Longer
Eat, Fast and Live Longer - Horizon from Steve Hartman on Vimeo.
Tuesday, June 1, 2010
The Anti-Aging revolution
In early 1934, Depression-weary Americans were beginning to see tendrils of hope poking out of the bleak landscape. President Franklin D. Roosevelt's New Deal was bringing the economy back from the dead. Galvanized by the sight of elderly women scrounging for food from garbage, California physician Francis Townsend had launched a crusade for government-funded pensions that would soon spur the creation of Social Security. Things were even looking up for the long-suffering Washington Senators, who had made it to the World Series the previous fall.
But one of the new year's most promising developments passed almost unnoticed. According to a brief article in the Jan. 13 Science News Letter, Cornell University researcher Clive McCay was nearing the end of a four-year study that showed that rats' life spans were greatly extended when they were put on near-starvation diets.
To many of his scientific peers, McCay's data made no sense at all. A glorious new chapter in nutrition science had been opened not long before by the discovery of dietary deficiencies behind scourges such as rickets, pellagra, and beriberi. In the wake of such progress, it seemed almost subversive to suggest that a bunch of rodent Oliver Twists, raised on such short rations that their growth was stunted, could live radically longer than well-fed ones. McCay sheepishly acknowledged in his initial report that his results seemed "little short of heresy."
Over the next several decades, his discovery was all but forgotten outside of the back halls of science -- a laboratory curiosity that didn't actually spark much curiosity. Most scientists were reluctant to risk wasting time probing an anomaly that seemed as baffling as aging itself.
Calorie restriction (CR), as it's now called, eventually was shown to extend many species' life spans by a third or more. Now that anti-aging research is hot, it seems bizarre that CR spent decades on science's back shelf. Simply put, McCay showed that the rate of aging is incredibly plastic, and that it's supremely simple to brake it in animals whose inner workings aren't all that different from ours. No biomedical discovery of the past century was more astonishing or significant.
So here's a prediction: McCay will someday be recognized as one of the last century's most important discoverers. He wasn't a genius with a capital G. But his skinny rats had made history with a capital H.
The idea of mimicking CR with drugs -- and without the hunger pangs that discourage most people from trying it -- finally got traction in the late 1990s when scientists began getting hints on the kinds of compounds that might work. (It had always been clear that such medicines were needed to make CR's broad health- and longevity-enhancing effects available to the masses, but before then researchers knew too little to get started.) Around 2000 several biotech startups were formed to pursue CR mimetics, including LifeGen Technologies of Madison, BioMarker Pharmaceuticals of San Jose, and GeroScience of Pylesville, Md. This first wave of CR-mimetic companies have been low-profile affairs compared with Sirtris Pharmaceuticals, the Cambridge, Mass., biotech juggernaut formed a few years later to develop drugs based on resveratrol, the famous red-wine compound shown to induce CR-like effects in animals. (Sirtris was acquired by GlaxoSmithKline in 2008.) They haven't been idle, though. GeroScience has worked with Procter & Gamble's (PG, Fortune 500) pet food unit, for example, on CR mimetics for pets, including a sugar in avocados called mannoheptulose. I wouldn't be surprised to see Fido and Muffy launch the era of effective anti-aging medicines.
The startups also deserve credit for beginning to transform the anti-aging quest from a guessing game into a fairly routine exercise in drug development. Before the pursuit of CR mimetics took off, most anti-aging investigators were like blind magicians trying to pull rabbits from a barrel of snakes. Not surprisingly, even the serious scientists among them often wound up covered in snake oil, promoting "breakthroughs" such as monkey-testicle implants and radium-laced elixirs.
CR-mimetic developers don't have to solve the monster problem of how aging happens in order to devise interventions that oppose it. Evolution has solved the problem for them. It did so while fashioning CR's machinery, which is poised to carry out all the intricate metabolic adjustments necessary to brake aging when activated by a true CR mimetic. Such drugs will be designed to switch on an ancient, enormously complex mechanism embedded in our genomes to postpone, and possibly attenuate, a myriad of ills brought on by aging: dementia, heart disease, cancer, as well as wrinkles, arthritis, age-related loss of muscle and bone, and the onset of senior moments. In effect, they'll represent the biggest free lunch in medical history. And given that compounds capable of emulating key effects of CR in rodents have already come to light, it's arguable that the Great Free Lunch's appetizers are now on the table.
Just a few weeks before his death in 1996 at age 100, George Burns was still enjoying life, cracking wise at a Christmas party thrown by Frank Sinatra. France's Jeanne Calment, who holds the record for longevity (she died in 1997 at 122), was similarly droll and unsinkable. When a reporter at an annual party in her honor departed with the words "Until next year, perhaps?" she shot back, "I don't see why not! You don't look so bad to me."
Very old people with such élan are obviously rare. But I suspect that many who retain mental clarity in late life make their way toward something like Burns' and Calment's radiant rapprochement with old age. Surveys show that self-reported happiness among older people in reasonably good health is generally higher than among younger groups. I don't want to sugarcoat old age -- it isn't for sissies, as they say. But I'd love to see more well-tempered sages like Burns in the world. Call it the George Burns scenario.
Some critics argue that developing anti-aging drugs is likely to engender a disastrous surfeit of needy oldsters gripped by greed and ennui. Leon Kass, a University of Chicago professor who chaired the President's Council on Bioethics under George W. Bush, has asserted, for instance, that "the desire to prolong youthfulness [is] an expression of a childish and narcissistic wish incompatible with devotion to posterity." Some naysayers add that "greedy geezers" will rack up ruinous Medicare and Social Security bills. Worse, they argue, the drugs may simply drag out late-life morbidity, recreating en masse something like the Greek myth of Tithonus, who was granted eternal life but not everlasting youth and wound up miserably withered forever.
I regard such visions as ill-founded. For one thing, there's evidence that CR mimetics would buy us quality time, not prolong misery. A study of CR's effects in rhesus monkeys has shown that it reduces age-related diseases by about a third in the primates during their later lives -- the calorie-restricted monkeys have greater lean muscle mass, significantly less age-related brain atrophy, half as much cancer, and half as much cardiovascular disease as do peers on normal diets. The world's longest-lived human population, natives of Japan's Okinawa prefecture, whose scant traditional diets are regarded as tantamount to mild CR, have 80% less breast and prostate cancer at advanced ages than North Americans do, suffer about 40% fewer hip fractures, and experience half the rate of dementia between 85 and 90.
It's possible that anti-aging drugs would compress late-life misery, letting us reach a ripe old age in good shape before a speedy demise. That could have huge economic and social payoffs -- much greater, for instance, than a miracle cure for all cancers.
Even if the medicines only postponed aging's deterioration, boosting life expectancy by, say, a decade, the benefits would be monumental. As Richard Miller, a University of Michigan gerontologist, says, "When you ask people, 'Would you like to live to 100?' they picture what today's elderly, infirm person looks and feels like. But the proper question is a different one: 'Would you like to add another 10 or 20 years to the middle of your life, so you reach 80 or 90 in the same condition that people generally are today at around 60 or 70?' "
A drug that increases healthy life-years would deliver large benefits across many sectors of the economy. Healthier, longer-living people can stay in the workforce longer, preserving skilled human capital that might otherwise be lost. Healthier workers are physically and mentally more robust, making them more productive. They're motivated to invest more in developing their skills, because they expect to reap the benefits of such investments for longer periods. They save more for retirement, boosting capital formation that fuels economic growth. They pose lighter burdens on federal entitlement programs and contribute more in federal and state tax revenue. Such factors probably explain why per-capita incomes of nations around the world have long risen in tandem with their populations' life expectancies.
Anti-aging drugs may well have downsides too. For instance, nest eggs that once seemed adequate may prove too small in an era of extended life spans. But the drugs should also help with that problem by keeping us vibrant enough to work after 62, the average age at which U.S. workers have retired in recent years. Of course, it remains to be seen whether the economy will support demand for older workers' services. Still, surveys show many baby boomers expect to work at least part-time in retirement for both fiscal and personal-fulfillment reasons -- they apparently agree with a piece of wisdom George Burns expressed late in life: "As long as you're working, you stay young."
Where does the anti-aging quest stand? As always with cutting-edge science, the quest has had ups and downs. In 2008, Harvard's David Sinclair and colleagues reported that resveratrol failed to extend the life spans of mice on normal diets, suggesting that it is at best a partial CR mimetic -- the group had earlier made a splash by showing that the compound induces CR-like effects in mice on high-fat diets. But last year a major turning point was reached: Researchers showed for the first time that a drug could convincingly extend life span in mammals.
The drug was rapamycin, a medicine long prescribed to help prevent rejection of transplanted organs. In parallel mouse experiments in three different labs, scientists funded by the National Institute on Aging found that rapamycin dramatically boosted longevity in mice on normal diets in a way reminiscent of CR's effects. Stunningly, the study showed that when rodents were first put on the drug at 20 months of age, roughly equivalent to 60 years in humans, the life expectancies of males were boosted by 28%, and that of females by 38%. Even CR itself hasn't been shown to exert such large effects on animals so close to the end of their lives. Former perma-bears about the anti-aging quest are now sounding upbeat.
Unfortunately, the drug industry has shown little interest in trying to translate such breakthroughs into anti-aging medicines. Both drug regulators and the medical establishment still essentially view aging as totally mysterious, inexorable, and intractable -- they wouldn't dream of adding it to the official list of drug indications. Thus, drug companies have no way to develop anti-aging compounds as high-margin prescription drugs. And that means that spending many hundreds of millions of dollars on clinical trials of the drugs' efficacy just doesn't compute. (The relatively small proceeds from marketing them as low-margin dietary supplements can't justify such costly, high-risk trials either.)
Besides, vetting the drugs would require first developing reliable biomarkers of aging, telltale signs of normal bodily decline over time that could be used to register how fast people are going downhill. Such biomarkers would enable the vetting of CR mimetics' efficacy in trials that last only a few years, rather than the impossibly long time it would take to assess their longevity-boosting effects in humans.
In short, the hugely promising anti-aging quest is now stuck between the R and the D stages, and I fear it will stay there until the federal government greatly steps up funding in the area. I, for one, don't plan to take purported CR mimetics until there's some reasonably rigorous clinical trial data showing that they're safe and effective. And until such data are available, the anti-aging revolution is likely to remain little more than the enthusiastic pursuit of placebo effects by wishful thinkers.
All this is terribly ironic. In effect, it means that authorities charged with promoting public health are fatalistically standing and watching the "silver tsunami" of population aging -- with its huge economic and human costs -- bearing down on us as if there were no way to shelter ourselves from its full force. Meanwhile, the authorities are perfectly willing to devote many billions of dollars annually to the pursuit of ever costlier palliatives for diseases of aging, which are typically applied when it's too late to do much good -- the federal government now annually spends less than 0.04% as much on research about the biology of aging as it does on Medicare.
So here's the moral of the story: The George Burns scenario is within our grasp if we collectively recognize what has happened in aging science and seize the day. And while anti-aging drugs may not enable all of us to live as long as Burns, they promise to let many of us age as gracefully as he did and thus aspire to our own version of his timelessness. As Burns once quipped, "You can't help getting older, but you don't have to get old." Words to remember from a wise guy to the end.
Thursday, February 4, 2010
7 ways fasting can rev up your fat burning furnace
1. Increases Fat Burning Hormones
Hormones are usually at the root of most of your metabolic functioning, and fat burning is no different. Growth Hormone is the most important fat burning hormone in your body. Fasting pushes growth hormone production into high gear and this makes your fat burning furnace start to work overtime. Fasting also decrease your insulin levels, which ensures that you burn body fat instead of storing it.
2. Increased Fat Burning Enzymes
Fat burning hormones need the help of fat burning enzymes to get their job done. Fasting will sky rocket the activity of two of the most important fat burning enzymes in your body. Adipose tissue HSL (Hormone Sensitive Lipase) is the enzyme responsible for allowing your fat cells to release fat so it can be burned as energy in your muscles. Muscle tissue LPL (Lipoprotein Lipase) is the enzyme responsible for allowing your muscle cells to take up fat so it can be burnt as a fuel. Fasting increases both of theseenzymes to optimize fat burning – A perfect combination.
3. Burn More Calories
Short term fasting (12-72hrs) actually increases your metabolism and adrenaline levels. This causes you to increase calorie burning during the fast period. The more calories you burn the faster you can lose weight. The extra energy you get from the fast might actually help you through a workout or get more work done at work or around the house. When I did my first fast I was shocked at how awake and energetic I was. My fasting days are now my most productive days of the week.
4. Burn Fat Instead of Sugar
Fasting shifts your metabolism from burning blood sugar to burning mostly body fat. When you eat a meal your body likes to burn carbs first, then the fat from your food. Any extra fat that your body can’t burn in the few hours after you eat get stored as body fat. When you fast your body has no choice but to burn stored body fat. By the end of a 24 hour fast your body is burning way more fat than it would during a regular day of eating.
5. You’ll Find Out Why You Eat
The most surprising benefit people report back when they start fasting is a new found awareness of what causes them to eat. When you make a conscious decision to fast for a day your less than flattering eating motivations become painfully obvious. This is the first and most effective step to getting rid of bat habits for good. Knowing what your motivations are for poor eating choices is essential before you can change them and build better habits.
6. Builds Positive Attitudes Towards Yourself and Food
Each short fast is an accomplishment that can build self confidence and gratitude. At the end of a 24 hour fast you can feel good about your accomplishment and start feeling good about your relationship with food again. The positive empowerment from each fast builds on the last until you feel completely in control of your food choices.
7. Eat All The Foods You Love Guilt Free
Short term fasting allows you to lose weight and burn fat without restricting any of the foods you love to eat. With this style of eating you can consume any and all of the foods you like whenever you choose without feeling guilty about it and still lose weight. You will never again have to be sitting in a restaurant picking at a salad while everyone else at the tables indulges in their favorite entrée and dessert.
Eating for fat loss doesn’t need to be complicated and food should never be a source of anxiety or guilt. Mixing in a few 24 hours fasts to your week can liberate you from the dieting prison and allow you to enjoy food again.
Wednesday, January 20, 2010
ADF and Exercise
fasting exercise and blood sugar
http://bradpilon.com/healthy-ramblings/fasting-exercise-and-blood-sugar/
Here are two quick “Did you knows?” concerning fasting, exercise and blood sugar.
Did you know that it takes 30 to 60 minutes of running at 75% of your V02 max (for conditioned runners) to get your blood insulin levels down to the same level found in people who have been fasting for 23 hours? (Dohm LG 1986)
Did you know that when scientists studied people who exercised after fasting for 23 hours, their blood sugar levels were actually found to be slightly higher then when the same people exercised after a small meal? (Coyle EF 1985; Dohm LG 1986)
What this means to you- running at 75% of your VO2 max for as long as 70 minutes in well trained runners who had been fasting for 23 hours did not cause hypolgycemia (low blood sugar) So if you like exercising while you are fasted, this research suggests you don’t have to worry about hypoglycemia (as long as your exercise intensity isn’t way above these levels).
And it takes between 30 and 60 minutes of running at a VO2 of 75% to get the same insulin lowering effect as simply sitting around the house after fasting for 18-24 hours.
Two things to think about the next time you are fasting.
other great entries can be found at the links below:
- fasting and exercise (http://bradpilon.com/healthy-ramblings/fasting-and-exercise/)
- fasting and atheltic performance (http://bradpilon.com/healthy-ramblings/fasting-and-athletic-performance/)
Dohm GL, Beeker RT, Israel RG, Tapscott EB (1986) Metabolic responses to exercise after fasting. Journal of Applied Physiology, Vol 61, Issue 4 1363-1368
Abstract
Fasting before exercise increases fat utilization and lowers the rate of muscle glycogen depletion. Since a 24-h fast also depletes liver glycogen, we were interested in blood glucose homeostasis during exercise after fasting. An experiment was conducted with human subjects to determine the effect of fasting on blood metabolite concentrations during exercise. Nine male subjects ran (70% maximum O2 consumption) two counterbalanced trials, once fed and once after a 23-h fast. Plasma glucose was elevated by exercise in the fasted trial but there was no difference between fed and fasted during exercise. Lactate was significantly higher (P less than 0.05) in fasted than fed throughout the exercise bout. Fat mobilization and utilization appeared to be greater in the fasted trial as evidenced by higher plasma concentrations of free fatty acids, glycerol, and beta-hydroxybutyrate as well as lower respiratory exchange ratio in the fasted trial during the first 30 min of exercise. These results demonstrate that in humans blood glucose concentration is maintained at normal levels during exercise after fasting despite the depletion of liver glycogen. Homeostasis is probably maintained as a result of increased gluconeogenesis and decreased utilization of glucose in the muscle as a result of lowered pyruvate dehydrogenase activity.
Modified alternate-day fasting and cardioprotection
Abstract
The relation between alternate-day fasting (ADF) and cardioprotection remains uncertain. In the present study, we examined the ability of modified ADF, with a low-fat (LF) vs high-fat (HF) background diet, to modulate adipose tissue physiology in a way that may protect against coronary heart disease. In a 4-week study, male C57BL/6 mice were randomized to 1 of 3 groups: (1) ADF-85%-LF (85% energy restriction on fast day, ad libitum fed on feed day, on an LF diet), (2) ADF-85%-HF (same protocol but HF diet), and (3) control (ad libitum fed). Throughout the study, body weight did not differ between ADF and control animals. Proportion of subcutaneous fat increased (P < .01), whereas the proportion of visceral fat decreased (P < .01), in both ADF groups. Triglyceride (TG) synthesis was augmented (P < .05) in subcutaneous fat, but remained unchanged in visceral fat. Adiponectin concentrations were elevated (P < .05), whereas leptin and resistin levels decreased (P < .05). Aortic vascular smooth muscle cell proliferation was reduced (P < .05) by 60% and 76% on the LF and HF diets, respectively. Plasma total cholesterol, TG, and free fatty acid concentrations also decreased (P < .05). In summary, modified ADF regimens alter adipose tissue physiology (ie, body fat distribution, TG metabolism, and adipokines) in a way that may protect against coronary heart disease. These beneficial effects were noted over a wide range of fat intake, suggesting that ADF may be protective even in the presence of HF diets.
Caloric restriction delays disease onset and mortality in rhesus monkeys
Colman RJ, Anderson RM, Johnson SC, Kastman EK, Kosmatka KJ, Beasley TM, Allison DB, Cruzen C, Simmons HA, Kemnitz JW, Weindruch R. (2009) Caloric restriction delays disease onset and mortality in rhesus monkeys. Science. 2009 Jul 10;325(5937):201-4.
Abstract
Caloric restriction (CR), without malnutrition, delays aging and extends life span in diverse species; however, its effect on resistance to illness and mortality in primates has not been clearly established. We report findings of a 20-year longitudinal adult-onset CR study in rhesus monkeys aimed at filling this critical gap in aging research. In a population of rhesus macaques maintained at the Wisconsin National Primate Research Center, moderate CR lowered the incidence of aging-related deaths. At the time point reported, 50% of control fed animals survived as compared with 80% of the CR animals. Furthermore, CR delayed the onset of age-associated pathologies. Specifically, CR reduced the incidence of diabetes, cancer, cardiovascular disease, and brain atrophy. These data demonstrate that CR slows aging in a primate species.
On the left is Canto (27) and on the right is Owen (29). Canto is fed with about 30% less calories than Owen (CR).
QOD
from eatQod.com
From the website: The QOD Diet™: Eating QOD is a way to lose weight gradually without pushing your body into starvation mode.Eating QOD allows you to eat pretty much what you want (within reason and without binging) every other day (ON days), so you don’t need to feel deprived. In between, during the OFF days, you need to limit food intake to 300-400 nonprotein calories, plus about 200 calories from protein, but your mineral intake (sodium, potassium, and calcium) should be kept constant.
From the LATimes: Feast, fast and reduce risks
http://www.latimes.com/features/health/la-he-eat10dec10,1,883044.story
Feast, fast and reduce risks
An irregular eating cycle worked for ancient humans. Small studies show benefits in such calorie restriction.
By Susan Bowerman, Special to The Times
Our hunter-gatherer ancestors spent hours each day searching for food that was only intermittently available. They'd fast, and then they'd feast. These ancient humans developed a "thrifty" genotype that helped them adapt to these cycles of want and plenty.
Today, we carry this same genetic makeup with us, and several animal studies and few small human trials indicate that there may be, for us too, health benefits to alternate-day fasting -- a regimen that somewhat mimics the irregular and unpredictable food intake pattern on which our ancestors evolved.
Evidence has been accruing for some time that chronic calorie restriction, in which daily intake is reduced to between 60% and 85% of an individual's daily needs, appears to have significant health benefits. Such restriction has been shown to reduce risk factors for several chronic diseases in animals and humans and to increase life span in rats, mice, fish, flies, worms and yeast.
But the effects of alternate feast and fast days on body weight and health have only recently been explored.
In a study published in the American Journal of Clinical Nutrition in 2005, scientists at the Pennington Biomedical Research Center examined the effects of alternate-day fasting on heart disease risk in 16 subjects.
Subjects ate whatever they wanted on feast days but consumed only calorie-free beverages and sugarless gum on fast days. After three weeks, blood levels of triglycerides fell in men, but not in women. Women, but not men, experienced increases in "good," or HDL, cholesterol.
There was no clear explanation for the differing results between men and women, but the same group of scientists have observed other sex-specific effects. In a different report, they measured the rise in insulin and blood sugar levels in response to a meal before and after three weeks of alternate-day fasting.
Men -- but not women -- had increased insulin sensitivity so that they cleared sugar from the bloodstream more efficiently after three weeks on the regime, suggesting that alternate-day fasting may be more beneficial to men than women in reducing the risk of Type 2 diabetes.
Similar improvements in insulin sensitivity were observed after two weeks of alternate-day fasting in a small study of eight male subjects at the University of Copenhagen, published in the Journal of Applied Physiology in 2005.
The effects of alternate-day fasting on body weight differ according to the study (and none have been reported in overweight people). Men in the Copenhagen study maintained a stable body weight over the two week period -- but they were specifically instructed to attempt to do so.
In the Pennington study, subjects were informed that they would need to double their usual intake on non-fasting days in order to maintain their weight. But taking in enough food on the feasting days to avoid weight loss proved difficult. The participants lost about 2.5% of their initial weight and 4% of their initial fat mass.
All in all, the few human studies on alternate-day fasting have been small in size, short in duration and have lacked control groups so more studies are warranted. Still, the animal studies suggest that the effects of alternate-day fasting on chronic disease prevention are similar to those reported for chronic calorie restriction.
How such dietary calorie restriction may impart its benefits is not clear, but it may include increased resistance to stress, a reduction in free-radical production (which in turn reduces cellular damage) or the slowing of certain metabolic processes that might damage the body.
From a practical standpoint, it's unclear whether people could stick to an alternate-day fasting regimen for any length of time. Researchers have suggested that the regimen is easier than daily calorie restriction, but is it easy enough? Many subjects in the Pennington study reported feeling hungry and irritable on the days they fasted -- and that would probably limit the number of people who could sustain this pattern of eating for very long.
Anyone wishing to attempt either chronic or alternate-day calorie restriction needs to remember that consuming nutrient-dense foods is key. There are no extra calories to spare, so every bite of food needs to be packed with nutrition.
But a carefully planned diet based on vegetables and fruits, lean proteins, a few whole grains and small portions -- rather than a continuous and abundant food intake -- may be a better nutritional match for those "thrifty" genes.
Susan Bowerman is a registered dietitian and assistant director of the UCLA Center for Human Nutrition.
Musing Forces blog
There are also great alternate day fasting links and resources on this blog.
http://musingforces.blogspot.com/
From ScienceNews.org: Possible anticancer power in fasting every other day
http://www.sciencenews.org/view/generic/id/40242/title/Possible_anticancer_power_in_fasting_every_other_day
Fasting every other day reduces some hallmarks of cancer in mice, even when the mice voraciously consume high-fat food between fasts, a study in an upcoming Nutrition shows.
Scientists have known for decades that eating fewer calories — roughly 25 to 50 percent less than recommended — extends life span in animals ranging from worms to dogs. But, “caloric restriction on a daily basis is very hard,” says Eric Ravussin, a physiologist at the Pennington Biomedical Research Center in Baton Rouge, La., who studies caloric restriction.
Last year, researchers including Krista Varady, then of the University of California, Berkeley, published a study suggesting that a less drastic version of caloric restriction provides a constellation of health benefits in mice. Called alternate-day fasting, the regimen of eating as much food, low-fat in this study, as one wants one day but fasting the next confers some of the same anticancer benefits as just cutting calories at a constant rate, the team found.
But for people, eating a low-fat diet one day and fasting the next is still challenging. Varady and her colleagues wanted to know whether the diet could be made easier to swallow and still provide similar benefits.
In the new study, Varady and other researchers compared mice who fasted every other day, both on high-fat and low-fat diets, to mice that didn’t fast but instead ate a low-fat diet every day. The mice on the ultimate yo-yo diet ate high-fat food, in which 45 percent of the calories came from fat — comparable, Varady says, to human diets of fast food and processed food.
On the fasting days, mice were fed 15 percent of their required calories from either the high- or low-fat food.
The results were surprising, says Varady. Mice that ate the rodent equivalent of Big Macs every other day showed the same anticancer benefits of fasting as the mice that ate the low-fat diet every other day. High rates of cell division — a key feature of cancer — were lower in the mice who fasted every other day than in mice that had not fasted. Mice who fasted every other day also had reduced levels of IGF-1, a protein that induces cell growth and has been linked to cancer.
The new study on mice is the “next installment in a systematic and interesting series of studies” from the researchers, comments James Johnson, a doctor affiliated with the Louisiana State University Health Sciences Center and studies alternate-day fasting in humans.
The option to eat high-fat meals while fasting every other day may make people more likely to stick with the demanding diet regimen, researchers say. To date, only three small studies have examined the effects of alternate-day fasting on people, says Varady, now at the University of Illinois in Chicago.
She says the next step is to see whether an unrestricted high-fat diet one day and a small amount of food the next will confer the same health benefits in humans as it does in mice. Varady and her colleagues are currently conducting a study to test whether humans are able to stick with such a diet. Preliminary data suggest that they can.
“The alternate diet has a lot of potential,” comments Valter Longo, a University of Southern California in Los Angeles researcher who studies aging. But, he adds, “I seriously doubt that very many people would adopt it because it is very tough to do regularly.”
Ravussin knows the difficulty firsthand. When he attempted alternate-day fasting himself, he reported feeling very irritable and hungry. “My wife told me, ‘Don’t do it again.’ ”
Alternate-day fasting and chronic disease prevention: a review of human and animal trials
http://www.ajcn.org/cgi/content/full/86/1/7
Abstract
Calorie restriction (CR) and alternate-day fasting (ADF) represent 2 different forms of dietary restriction. Although the effects of CR on chronic disease prevention were reviewed previously, the effects of ADF on chronic disease risk have yet to be summarized. Accordingly, we review here animal and human evidence concerning ADF and the risk of certain chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. We also compare the magnitude of risk reduction resulting from ADF with that resulting from CR. In terms of diabetes risk, animal studies of ADF find lower diabetes incidence and lower fasting glucose and insulin concentrations, effects that are comparable to those of CR. Human trials to date have reported greater insulin-mediated glucose uptake but no effect on fasting glucose or insulin concentrations. In terms of cardiovascular disease risk, animal ADF data show lower total cholesterol and triacylglycerol concentrations, a lower heart rate, improved cardiac response to myocardial infarction, and lower blood pressure. The limited human evidence suggests higher HDL-cholesterol concentrations and lower triacylglycerol concentrations but no effect on blood pressure. In terms of cancer risk, there is no human evidence to date, yet animal studies found decreases in lymphoma incidence, longer survival after tumor inoculation, and lower rates of proliferation of several cell types. The findings in animals suggest that ADF may effectively modulate several risk factors, thereby preventing chronic disease, and that ADF may modulate disease risk to an extent similar to that of CR. More research is required to establish definitively the consequences of ADF.
