How would you like it if I told you there was a way to eat pretty much anything and everything you wanted to eat and still maintain your health? Or better yet, what if I told you that you could eat pretty much anything and everything you wanted and even improve your health? Would you be interested? I figured as much.

There is a way to reduce blood sugar, improve insulin sensitivity, reduce blood pressure, increase HDL levels, get rid of diabetes, live a lot longer, and still be able to lose a little weight. All without giving up the foods you love. And without having to eat those foods in tiny amounts. Sounds like a late-night infomercial gimmick, but it isn’t.

Before I get to the real nitty gritty of how such a thing can be done, let’s look at a method that has been proven in countless research institutions to bring about all the above-mentioned good things. It’s called caloric restriction.

When researchers restrict the caloric intake of a group of lab animals to about 30 to 40 percent of that of their ad libitum (all they want to eat) fed counterparts, they find that the calorically restricted animals live 30 percent or so longer, don’t develop cancers, diabetes, heart disease, or obesity. These calorically restricted (CR) animals have low blood sugar levels, low insulin levels, good insulin sensitivity, low blood pressure and are, in general, much healthier than the ad lib fed animals.

Most of the work in caloric restriction has been done on rodents, but there is a long term study on Rhesus monkeys (17 years at this point) that appears to confirm the rodent data on longevity and health with CR in primates. There are no human longevity studies, but there are a number of human studies on CR and health that show that human subjects under CR conditions reduce blood sugar, improve insulin sensitivity, reduce blood pressure, etc., so it stands to reason that if humans reduced their caloric intake by 30-40 percent for their entire lives, they would also live longer.

Caloric restriction is a terrific way to lose weight and get healthy; problem is, it’s not much fun. When rats live out their little ratty lives calorically restricted in their cages they seem to show signs of depression and irritability. Primates do for sure. If primates don’t get enough cholesterol, they can actually become violent. But, if you’re willing to put up with a little irritability, hostility and depression, it might be worth cutting your calories by 30 percent for the rest of your long, healthy miserable life.

Doesn’t sound so cheery? You’re not ready to sign up yet?

Well, there is a better way.

A number of different research teams have studied a method by which rodents can get all the health and longevity benefits of caloric restriction without calorically restricting. And the method has been studied in humans and seems to achieve the same health benefits and, if an old Spanish study can be believed, maybe even an increase in lifespan.

What is this magic method?

Intermittent fasting.

In regular fasting one goes entirely without food, which is caloric restriction carried to the extreme. Going entirely without food in the short term leads to improvement in health, but also leads to an extremely short life unless the fast is aborted.

Intermittent fasting (IF) is just as its name implies: a period of fasting alternated with a period of eating.

But isn’t that what we do anyway? We eat breakfast, then fast until lunch. Then, after lunch, we fast until supper. Then we fast all night. Uh, not exactly.

In research settings animals that are intermittently fasted are fed every other day, so they eat whatever they want for a day, then they are denied food for a day. Interestingly, on feeding days most of the animals eat a almost double the amount that their ad lib fed mates do. Thus the IF animals eat about the same number of calories overall that the ad lib fed animals eat, but, and this is a huge ‘but,’ the IF animals enjoy all the health advantages that the CR animals do, and, in fact, are even healthier than the CR animals.

Like caloric restriction, intermittent fasting reduces oxidative stress, makes the animals more resistant to acute stress in general, reduces blood pressure, reduces blood sugar, improves insulin sensitivity, reduces the incidence of cancer, diabetes, and heart disease, and improves cognitive ability. But IF does even more. Animals that are intermittently fasted greatly increase the amount of brain-derived neurotrophic factor (BDNF) relative to CR animals. CR animals don’t produce much more BDNF than do ad libitum fed animals.

What’s BDNF? (The Wikipedia definition is actually pretty good)

BDNF, as its name implies, is a substance that increases the growth of new nerve cells in the brain, but it does much more than that. BDNF is neuroprotective against stress and toxic insults to the brain and is somehow–no one yet knows how, exactly–involved in the insulin sensitivity/glucose regulating mechanism. Infusing BDNF into animals increases their insulin sensitivity and makes them lose weight. Humans with greater levels of BDNF have lower levels of depression. BDNF given to depressed humans reduces their depression. And Increased levels of BDNF improves cognitive ability. In short, you want as much BDNF as you can get., and with IF you can get a lot.

But, who wants to go all day every other day without food?

Well, you don’t have to. MD and I, using ourselves (selflessly, I might add) as subjects have worked it out.

Most rodents feed throughout the day and night, so restricting them for 24 hours does just that: it restricts them for 24 hours. In humans, however, the situation is different. We humans, for the most part, eat only during our waking hours. So if we fast for a day, we end up fasting for about 34 hours and eating for 14, which isn’t the same as 24 on, 24 off.

Let me show you what I mean.

Let’s say you pick a day to start. You eat all day, then go to bed, wake up in the morning and fast all day, then go to bed. You wake up the next morning and eat all day, then go to bed and start again. So, assuming you eat until 10 PM on your eat day, once you quit eating you don’t eat again until 8 AM 34 hours later. If you eat from 8 AM that day until 10 PM, you’ve eaten for 14 hours. so, you’re on (eating) for 14 hours and off (fasting) for 34. MD and I spent a couple of weeks doing it that way, and I’m here to tell you, it’s no fun. At least not on the fast days. The eating days were a different story; they were great, but we would spend the entire day dreading the fast day coming up.

We fooled around with a number of different eat-fast-eat regimens and came up with something that works pretty well. We set up our cutoff time as 6 PM. On the day we started, we ate until 6 PM, then fasted until 6 PM the next day. On the next day we ate supper right after 6 PM and ate breakfast and lunch (and a few snacks) the next day until 6 PM when we started fasting again.

The advantage of this regimen is that we were able to eat every day. One day we would get supper–the next day we would get breakfast and lunch. On no days would we go entirely without food. This schedule worked the best for us.

On the times during the day that we ate, we didn’t stick with our normal low-carb fare; we ate pretty much whatever we wanted, including a fare amount of higher carb stuff. We stuck with the regimen for a few weeks just to see if we could tolerated it, which we did just fine. We ultimately drifted back to our normal low-carb diet, however, just because it seemed to work better with our schedules. We could have been happy on the intermittent fasting regimen for the long term.

I would think that the optimal way to go would be to follow an intermittent fast using low-carb foods during the eating periods. One would get the best of all worlds healthwise this way.

Over the period that we followed the various IF regimens we lost a little weight because, unlike the rodents, we couldn’t eat twice as much during the eating days as we would have eaten were we not fasting. We didn’t check any lab work to see if any values had changed. We weren’t doing a hard core study; we were simply evaluating IF as a practical means for humans to use to improve their health.

In thinking about the process I came to the conclusion that IF was probably the way Paleolithic man ate. We modern humans have become acculturated to the three square meals per day regimen. Animals in the wild, particularly carnivorous animals, don’t eat thrice per day; they eat when they make a kill. I would imagine that Paleolithic man did the same. If I had to make an intelligent guess, I would say that Paleolithic man probably ate once per day or maybe even twice every three days. In data gathered from humans still living in non-Westernized cultures in the last century, it appears that they would gorge after a kill and sleep and lay around doing not much of anything for the next day or so. When these folks got hungry, they went out and hunted and started the cycle again.

If you buy into the idea that the Paleolithic diet is the optimal diet for us today because it is the diet we were molded by the forces of natural selection to perform best on, then you should probably also buy into the idea that a meal timing schedule more like that of Paleolithic mean would provide benefit as well.

One of the things MD and I took away from our IF experience is the idea that we don’t have to eat three meals per day. We now often skip lunch and don’t seem any the worse for it. Sometimes we get up and get going with all our projects and don’t eat breakfast. We try to skip a meal here and there because figure it’s probably good for us. When you get used to it, you don’t really even think about it. And it’s good for you. Don’t take my word for it–look at the medical literature.

There have been a few human studies on IF, and all have shown a marked improvement in virtually every parameter tested. None of the subjects in any of these studies has done the full 24 on-24 off that MD and I did. Most fasted until 5 or 6 PM on the fast days, then ate, then ate regularly on the eat days. Even with this wimpy IF schedule the subjects did better.

One of the recent papers published on the less rigid IF schedules caught my eye because one of the authors was Don Laub, who used to be the chairman of the plastic surgery department at Stanford. When I was in medical school I thought I wanted to be a plastic surgeon so I went to Stanford during a part of my senior year and worked with Dr. Laub as my mentor.

In this study, published in the journal Medical Hypothesis in March of this year, Dr. Laub along with two other physicians (neither of whom I know) underwent their version of and intermittent fast. The three of them have since May 2003 been on a version of the IF in which they consume about 20-50 percent of their estimated daily energy requirements on the fast day and eat whatever they want on the non-fast days.

Since starting their regimen they have

observed health benefits starting in as little as two weeks, in insulin resistance, asthma, seasonal allergies, infectious diseases of viral, bacterial and fungal origin (viral URI, recurrent bacterial tonsillitis, chronic sinusitis, periodontal disease), autoimmune disorder (rheumatoid arthritis), osteoarthritis, symptoms due to CNS inflammatory lesions (Tourette’s, Meniere’s) cardiac arrhythmias (PVCs, atrial fibrillation), menopause related hot flashes.

In their paper these researchers discuss a 1957 paper from the Spanish medical literature.

…the subjects were eating, on alternate days, either 900 calories or 2300 calories, averaging 1600, and that body weight was maintained. Thus they consumed either 56% or 144% of daily caloric requirement. The subjects were in a residence for old people, and all were in perfect health and over 65. Over three years, there were 6 deaths among 60 study subjects and 13 deaths among 60 ad lib-fed controls, non-significant difference. Study subjects were in hospital 123 days, controls 219, highly significant difference. We believe widespread use of this pattern of eating could impact influenza epidemics and other communicable diseases by improving resistance to infection. In addition to the health effects, this pattern of eating has proven to be a good method of weight control, and we are continuing to study the process in conjunction with the NIH.

There is much more to the IF story that I will continue in another post. I would do it in this one, but I (actually my web guy) upgraded my blogging software and somehow the little buttons that let me link to other sites are AWOL. I can’t italicize or set off quotes or do any of the things I normally do in the course of posting. I’m hoping that I will get this straightened out soon. When I do, I’ll go into the subject in a little more detail and show a chart that demonstrates the difference between CR and IF. (Note: the problem is solved; all links are working.)

In the meantime, if any of the readers of this blog would like to undertake an intermittent fast, I would love to hear the results of the experience. Please send a comment.