Our Longevity Diet

Intermittent fasting, as the name implies, consists of alternating ‘eating time’ with ‘fasting time.’ Everyone does this naturally as part of their living cycle, even if ‘fasting time’ is only equivalent to the time you sleep. Most people wouldn’t consider that intermittent fasting, however. So let’s limit ourselves to fasts that last at least 12 hours.

Now, as it happens, 12 hours roughly corresponds to the hours of darkness in tropical regions, where the difference between the longest day of the year and the shortest is much less than in more temperate regions. So for our early ancestors, and our chimpanzee cousins, fasting 12 hours a day was probably the norm.

I don’t know if any studies have been done on such short-term fasting, but if so I haven’t seen them. For the health and longevity benefits associated with intermittent fasting, most people assume we need at least 18 hour fasts, and most people on intermittent fasting regimes fast longer than that. But in the end, there are no hard and fast rules, because research into this is in its early stages, and very few of the possible permutations have been explored.

Alternate Day Fasting

The term alternate day fasting (ADF) was coined by scientists to describe feeding patterns (indeed, they often use the interchangeable term ‘alternate day feeding’) that they subject experimental animals to in their research. As a type of intermittent fast, this term is usually misleading and confusing, since most people who follow what they call alternate day fasts are really just fasting part of every day — but the fasting parts of two days come together to make one long fast of about 24 hours. So they talk of ‘eating days’ and ‘fasting days’ but mean 24 hour periods by those terms, not calendar days.

It gets even more confusing because some people really do have eating days and fasting days on an ADF regime, but they don’t mean by these terms what common sense might dictate. These people have what I call asymmetric ADF regimes — they eat more on some days, and less on the alternate days. Again, most of them are fasting about 24 hours at a time, but they do so in a way that leaves them with more food (eating days) on some days and less (fasting days) on alternate days. So the fasting day is really a day when they eat less food, and they still fast part of the eating day.

Other people on ADF schedules try to balance the amount of calorie intake each day. A typical schedule of this type might follow the usual American meal pattern: these people eat dinner on day 1, then breakfast and lunch on day 2, after which they fast until dinner time the following day. If they ate the same as before the fasting was begun, they would be reducing their calories by 50%, but few people can long withstand such extreme calorie deprivation.

A third type of ADF diet does not try to restrict calories at all, but only limits the timing of those calories, so they are consumed outside the 24 hour fasting period in every 48 hours. This is the kind of fast we describe on the ‘our diet‘ page. We eat about the same amount of food as we always did, having one large meal and one small snack each day. For convenience, we only fast 23 hours, which allows us to have our main meal at the same time each day (between 2:00 PM and 3:00 PM). We refer to this by the generic term intermittent fasting, or use the numeric notation (hours fasting / hours eating) or ‘23/25 fast’ for a more descriptive name. But neither of these is really adequately descriptive, since we have found that timing of the fasting/eating hours is highly significant in determining how easily one can stick to the schedule. Calling it ADF is confusing beyond measure.

Partial Day Fasts

Another popular technique for implementing intermittent fasting is to simply eat during a short time period at the same time each day. Bert Herring popularized this with his ‘Fast-5′ diet plan, which calls for eating between 5:00 PM and 10:00 PM each day. This was intended as a weight-loss diet — the author recommends making the eating window longer when you reach your ideal weight. It is doubtful that any health or longevity benefit would come from such a lifestyle, if the fasting period were reduced to less than 18 hours each day (beyond the obvious weight-loss health benefits).

We have been experimenting with this type of diet, which we refer to as 19/5 using the numeric coding described above. Our experience, as you can see from earlier posts on this blog, suggests that timing is critical in making such a diet comfortable — we found eating late in the evening very difficult, while shifting the eating window to 2:00 PM to 7:00 PM has made it much easier. Still, this is a weight-loss diet, and not a lifestyle. I think the longer fasts of our 23/25 diet are probably healthier, and certainly easier to maintain over the long term.

Another partial day fast that is somewhat popular is simply eating one meal a day, and fasting the rest of the time — 23/1 schedule. I will have to reserve comment on that until I try it (which I’m not to anxious to do — it sounds very difficult), but I think for most people it would be too arduous to keep up such a schedule even for a few weeks to lose weight, let alone as a lifestyle. Maybe if you believe suffering is good for the soul — but I prefer to enjoy my life.

Long Term Fasts

There are a variety of long-term fasts undertaken for ‘cleansing’ or for rapid weight loss, but these are rarely repeated at such regular intervals to make them a form of intermittent fasting. One exception is a kind of alternate day fasting where they really do use calendar days — so they eat nothing all of one day, which combined with eight hours sleep the night before and eight hours sleep afterwards, make a total fasting period of about 30 to 32 hours out of each 48. Again, this may be a great weight-loss diet if you can keep with it, but I can not see it as a viable lifestyle option for most people.

Other non-intermittent fasts are outside of the subject area for this blog. Religious fasting, juice fasting — or any other fast that includes caloric nutriment consumption during the fast, such as cleansing fasts, as well as medical fasting prior to procedures, and all other occasional fasts are fundamentally different from, and unrelated to intermittent fasting. We will be discussing non-fasting weight-loss diets and other health-related matters here, but always in an effort to elucidate the effects and benefits of intermittent fasting.

Clearly, we should not need to make an either-or choice, but scientists wanted to know which was better for a long life: calorie restricted diet, or exercise? The research clearly shows caloric restriction is more beneficial for life extension than exercise.

The first caveat is that they were looking at mice, and however similar the mammalian physiology can be at times, mice are not humans. Second, note that this study looked at caloric restriction — not fasting. Now other studies have shown that fasting can confer all of the same benefits to health and longevity that calorie restriction does, but fasting was not examined in this study.

Earlier research had already shown that while rodents that got exercise lived longer than those that did not, it was the average lifespan that was longer, not the maximum age at death. So exercise helped prevent early death in some percentage of animals, but did nothing to extend the lifespan beyond the normal.

Comparing calorie restricted animals to those that got lots of exercise, the calorie restricted animals lived longer, exceeding the ‘normal’ average lifespan for the species. The purpose of this latest study was to see if they could find the reason behind these earlier results.

In the newly reported study, mice that ate as much as they wanted and got little exercise had the highest levels of insulin-like growth factor (IGF-1), while both exercise and calorie restriction lowered that. Insulin itself was high in both animals that ate freely and those that ate freely and exercised. Both exercise and caloric restriction lowered 8-hydroxyguanosine (8-OHdG) levels, the presence of which is indicative of DNA damage. In summary, only insulin levels were clearly associated with the longer life expectancy, though researchers are not suggesting that insulin alone was responsible for the difference.

The authors suggest that reducing calories produces beneficial changes in ‘hormone levels’ without being too specific about which hormones. The analysis goes on to say:

A handful of studies comparing calorie restricted people to people who are avid exercisers, found similar hormonal benefits among those eating less. However, calorie restriction studies are difficult to carry out in people because participants often complain of feeling hungry, lethargic, and cold.

Well yes, calorie restriction is difficult for humans. Why not study intermittent fasting instead? A properly scheduled intermittent fast without caloric restrictions is very easy to follow. Intermittent fasting with mildly restricted calories is also easier than the typical caloric restriction diet — which has people eating all the time, but too little food to ever be satisfied. Better a small eating window daily, and fasting the rest of the time. You can eat one satisfying meal, at least, which makes the entire process more tolerable. Finding enough randomly selected individuals for prolonged caloric restriction studies will be nearly impossible — the drop-out rate will skew any data collected. Intermittent fasting without calorie restriction is so easy, however, that a large study could be undertaken with no more difficulty than in any other human-based studies that require modified behavior.

Over on The IF Life blog, Mike OD suggests that those living a fasting lifestyle take one ‘up’ (non-fasting) day each seven to ten days. He thinks this will signal the body that there is no danger of starvation, and help prevent the build-up of Alpha-2 receptors on fat cells — the kind that make it hard to lose that fat.

From a psychological point of view, I don’t like that idea. First, I’m not sure why it is called an ‘up’ day, but it makes it sound like the rest of the days must be ‘down.’ I know how most people think about food, and I’m sure that for all too many folks an ‘up’ day would soon translate into a reward — which, again, makes all the other days seem somehow inferior. If you stick to the arduous fast for a full week, you reward yourself with an ‘up’ day.

If that is how you feel, you will never keep up with the fasting regime for the rest of your life — which is what the goal of a good fasting lifestyle should be. There are two broad categories of intermittent fasting — those whose fast includes calorie restriction, and those who fast but make no effort at restricting calories. Some people think that fasting with calorie restriction can be a permanent lifestyle, but I doubt that will work for more than a tiny minority of people. Instead, I think a calorie restricted fasting regime is a good temporary solution to help you lose weight more rapidly than you otherwise would. Perhaps if that is your goal, you may want to build in occasional reward days to help keep the weight-loss from plateauing out.

Once you are at or near your ideal weight, however, the less rigorous — and much less difficult — calorie unrestricted fast is your best choice for a permanent lifestyle. And if you follow a schedule that suites your lifestyle, you will be eating as much as you want half of every day — as we do on our 23/25 fast — so every day is an ‘up’ day. So long as you eat a normal, healthy diet, and get a reasonable amount of exercise, fasting will help you maintain your ideal body weight, while still reaping the health benefits attributable to caloric restriction.

Well, at the end of our first week on a 19/5 fasting schedule, our impression is that it is much more difficult than our earlier 23/25 schedule. Even though the fasts are a few hours shorter, we feel more hungry at the end of these fasts than under the other regime. That is logical enough, since we fast twice in every 48 hours this way, whereas the other method only had one fast in 48 hours.

Eating in a five-hour window is a bit strange — we eat our regular main meal at the start of the five-hour window, but we are not really hungry towards the end of that five hour span — yet we know we will soon be hungry, so we eat anyhow. This doesn’t seem like a good idea to me, to eat when you are not hungry is a very bad habit to get into. If we don’t eat, however, we might as well be on a 23/1 schedule — eating one meal per day and fasting 23 hours.

As mentioned earlier, we found the 19/5 fast far too difficult when the five eating hours came in the evening. Changing the schedule so that the eating hours come near the middle of our waking hours makes things much easier. We are just beginning to get hungry at bed-time, and still sleep soundly. If the sleep period were at the very end of the fasting period, I think it might be difficult to get to sleep. Eating between 2:00 PM and 7:00 PM works great, since we sleep from about 1:00 AM to 9:00 AM. Under this schedule I can imagine staying on this diet permanently, but suspect we will prefer going back to our 23/25 schedule in the long-term.

This Fast-5 diet was promoted as a weight-loss diet, and for me that has been the case. Isabel, however, had a bounce-back — hopefully just a temporary set-back. Over the week we were on the 19/5 fasting schedule Isabel gained back 1.4 kilo, while I lost .9 kilo. We will stay on this diet at least one more week before deciding if we will go back to 23/25 right away, or stay on this and try to lose some weight.

Although I only posted about our switch to the classic version of the Fast-5 diet yesterday, we have been on that schedule since Tuesday, so this is our fourth day, and we just can’t hack it. Isabel and discussed it, and this diet just leaves us too weak — we can’t do our work, or follow our normal exercise routine.

I don’t think it is the diet itself that is so hard, but the timing in the usual version is terrible. You go to bed before you are really hungry, and then have all day of the hard part of the fast during waking hours. So as of today we are moving our eating window forward several hours. From now onward, as long as we are following a 19/5 type fast, the eating time will be from 2:00 PM to 7:00 PM. This accomplishes two things — first, it allows us to eat at our accustomed time of 2:00 PM for our main meal of the day. Secondly, it moves the end of the fast, the hardest part, to just five hours in the morning and early afternoon. We go to sleep about 1:00 AM, so we only have six hours of fasting at that point, which means we won’t be too hungry and can get to sleep easily, but still have ‘used up’ a good portion of the total fasting time.

We will see how this adjustment goes. I don’t think it should make any difference to the weight-loss potential of this diet, though to be sure I would have liked to continue on the previous schedule for a full week — doing so would have ruined our weekend, and just isn’t worth it. For now we plan to continue with the 19/5 schedule for the rest of this week, and then one full week more — if we can — before we decide if we want to stay on 19/5 for a while or return to 23/25 that we undertook originally.

In either case, when we are satisfied with our weight we will probably go back to the 23/25 schedule, since I suspect the less frequent, but slightly longer fasts are probably more beneficial to health. In the next few posts I’ll review some more of the scientific research, and see what conclusions we can draw from that information.

The Fast-5 regime was developed by Bert and Judi Herring as a weight-loss diet. Bert wrote a short book about the diet in 2005, which may be bought through Amazon or downloaded from the author’s website. It is a very simple fast, with just one rule: you only eat during a five-hour window each day, typically between 5:00 PM and 10:00 PM.

Of course if you eat too much during that five hour window, you can still gain weight — but most people can learn to curb their consumption enough to shed some kilos. Once you reach your desired weight, the author recommends that you keep on the diet, but either eat larger meals, extend your five hour window to a slightly longer period, or fast only some days out of the week — whatever best suits your lifestyle. Of course if you go back to eating as you did before the diet, you will gain back the weight you lost.

This diet sounds harder to me than our 23 hour fast out of each 48 hours, but I thought we should give it a try, so we can evaluate it fairly. Compared to our original fast, this method is four-hours shorter for each fast, but there are two such shorter fasts in each 48 hour period, rather than just one. So Tuesday, May 6th, we switched to the classic Fast-5 style, and plan to eat only between 5:00 PM and 10:00 PM each evening for at least one week.

The author points out that there is nothing magical about that time period however, so for our second week of 19/5 fasting we plan to change the window to match our earlier eating habits, probably from 2:00 PM to 7:00 PM. At the end of each week we will report on this blog our impression of the fast. Then after the two weeks we will either go back to our original fasting schedule, or extend the 19/5 regime, whichever we feel is best for us.

Well, things did not exactly go as planned on our first long-distance trip while fasting. We didn’t get a lot of sleep the night before because we wanted to leave very early in the morning. Of course when we got to Chapala we had just missed the 7:00 AM bus, so we had to wait 45 minutes for the next one. From there it is an hour ride into Guadalajara, where the bus stops at what is known as the old bus station.

Most large Mexican cities have two bus stations, one for in-state travel, and one for inter-state. That is the case with Guadalajara. Of course they are located at as much distance from one another as possible, because having them side by side would be too convenient for travelers. From the old bus station we took a city bus to the (what else?) new bus station — another full hour, crawling across the city and stopping almost every block for passengers.

In the new bus station we only had to wait about half an hour for the next bus to Colima, which left at 10:30 AM. That bus takes half an hour just to cross Guadalajara, so about 11:00 AM we were leaving the city — we got up at 5:00 AM for an early start! The city of Colima is about four hours from Guadalajara by bus, but before we got there Isabel began to feel sick to her stomach. We were supposed to break our fast about the time we got to Colima, but by then she felt too ill to eat anything other than a small bread roll. I had a big sandwich and was feeling fine.

From the city of Colima we took another bus to Tecoman, almost an hour further toward the coast. There we got a hotel room and, since Isabel hadn’t eaten much of anything at Colima, we went to a restaurant for her to get a meal. I had some french fries and a beer while she ate a normal sized meal. I had hoped that would solve her stomach problem, but it wasn’t lack of food that was bothering her, as she continued to feel poorly that night and into the next day.

Our schedule called for resuming the fast the next day, but since we were going to our cottage in Cerro de Ortega that day, we had lots of work to do, and Isabel was still feeling ill. So we decided to abandon the fast for a day or two, until she felt better. We resumed our fasting schedule Sunday, when we made the trip back without stopping for food, and ate when we got home. Isabel was feeling fine again by then, and endured the same grueling trip in reverse without problem, so we assume she just had one of the short-term ‘bugs’ we all get from time to time. If she were at home and could rest, I would not consider that enough to stop the fast — indeed fasting might help cure the bug problem faster, but since we had lots of work (cleaning, moving furniture, we even planted a couple coconut palm trees) the combination of sickness and physical activity was too much to support on an empty stomach. I could have continued fasting, but it would be awkward since we were eating in restaurants. Also Isabel felt she would be ‘cheating’ if she ate when I fasted. In the end we only skipped one and one-half fast periods, but that (and the great seafood in Colima), was enough that I gained back half a kilo. Isabel continued to lose weight, since she was eating lightly because of her upset stomach.

The experience left Isabel with the opinion that fasting is just too difficult under the strain of travel. I suspect it would have been OK had she not gotten ill and if we were going for a restful vacation instead of working on refurbishing the cottage. It was more the combination of strains, rather than travel alone, that caused us to break the fast for a few days. I must admit that habit, too, plays a large part, as we are accustomed to ’splurging’ on our trips to Colima, where the shrimp cocktails, ceviche, and various other seafood dishes beckon us to the beach-front restaurants.