Our Longevity Diet

I continue to see references to Fast-5 as the most popular type of intermittent fasting, and have had people ask me why we don’t like it. To me, the worst feature of Fast-5 is that it encourages you to eat when you are not hungry. That seems a very bad lesson to learn. It is very un-natural, and must have negative consequences — though I’m not aware of it ever having been studies.

In the Fast-5 diet, you have a five hour ‘window’ during which you eat each day. If you have a large meal (i.e. supper) at the start of that time-span, you are probably just beginning to get a little appetite back five hours later. But before the five hours are up you need to eat again, knowing that you will not be able to eat for 19 more hours, so you force yourself to have another (admittedly smaller, but larger than you really want) meal.

Say you follow the exact schedule used in the book, and eat at 5:00 PM. You probably finish around 5:30 or 5:45, depending on the meal. Then, about 9:00 PM, just 3.5 hours after you finished your dinner, you think ‘Oh I better eat now, fasting starts in just another hour!’ — so you make a sandwich or other good-sized mini-meal, and eat it about 9:30, four hours after you finished dinner. You are not really hungry at all, and are just eating because it will be ‘too late’ if you wait until your appetite returns.

As I’ve stated before, that 5:00 PM to 10:00 PM eating schedule is also a poor choice, because you spend all day waiting for ‘feeding time’ and then go to sleep on a full stomach. Much better is to go to sleep just as you are getting hungry again. If your sleep hours are too late in the fast, hunger can make it hard to get to sleep, so you don’t want to go too far in that direction either. Put your sleep hours in the middle of the fast, and you will sleep away some of the most difficult hours, those when your appetite returns.

You may dream of food, but I assure you dreamed food is absolutely non-fattening. You will wake up a bit hungry, but you probably are used to that — most people are a bit hungry in the morning. That feeling will persist until the end of the fast — but it will not become a gnawing pain or severe longing, because you know it is not very long until you will eat again.

The other problem with Fast-5 is that it forces calorie restriction. That is fine if you goal is rapid weight-loss, but it is a short-term means to an end, rather than a satisfying lifestyle choice. The recommendation that you should only fast a couple days a week once you have achieved your ideal weight is not satisfactory, because it unbalances your life. Suddenly you have two days each week that you dread, because they are a break from your norm.

It is easier and more satisfying to fast 23 or 24 hours out of each 48. You are fasting less than the Fast-5 but the fasts are slightly longer, and may be more beneficial for that. I say that purely from conjecture, since nobody has studied 19 hour daily vs 23 or 24 hours of each 48 fasting. I suspect the results would be so similar that a very large study-group would be required to have any statistically meaningful results from such a study. My feeling is that the slightly longer fasts probably have slightly more beneficial effect, and that is negated by the lower frequency, so the two fasting styles even-out about the same. Give me two roughly equivalent choices, and I tend to choose the easier — and from experience Isabel and I say our 23/25 schedule is much easier than Fast-5.

There are dozens of different popular intermittent fasts, and hundreds more variations possible. But in general, they divide themselves into two major groups: intermittent fasting with calorie restriction, and intermittent fasting without calorie restriction. Basically, these are like they sound — in the first, you not only limit when you eat, but you try to structure it so that you eat less calories during your eating times than you had prior to taking up the fast. With calorie unrestricted fasts, you still limit when you eat, but you try to structure it so that during your eating times you have just as much food as you normally would if you were not fasting.

We are following a schedule that is calorie unrestricted. Yet we still manage to lose weight. How can that be? Well first, there is not a complete correlation between calories consumed and calories used by your body. That assumes 100% absorption of calories by your digestive system, which is unrealistic. Human waste may not be high enough in calories to cook on, like cow manure, but I’m sure it has some calories in it. Perhaps after fasting it has more — I’m really in no position to test that, but merely suggest it as a possibility.

Another possibility is that we are eating less, but just don’t realize it. We eat the same main meal as before, plus a small meal or snack — breakfast on alternate days and an evening snack on the days we don’t eat breakfast. But during fasts we eat nothing, so there is no temptation to snack between meals, because we are not eating meals then. And when we are in the eating period, we are much more aware of our food consumption. We still may have an occasional handful of nuts or piece of fruit for a snack, but probably not as often as we did before taking up the fast.

Some people say your stomach ’shrinks’ when fasting. I don’t know if this is literally true (the stomach is capable of expansion, so it makes sense it can get smaller too, when not kept as full as previously) but it certainly is an accurate description of how it feels — you just don’t want to eat too much, and have less desire for between-meal snacks.

So, of the two types of fast, intermittent fasting without calorie restriction can still lead to weight loss, though slowly and gradually — it is more likely to be permanent loss then temporary weight-loss diets provide. Intermittent fasting with calorie restriction should lead to more rapid weight loss, though for us that was not the case when we temporarily switched to a Fast-5 style diet. Regardless, it seems logical that a calorie restricted diet would be much more difficult to maintain over long periods, and should not be considered for a lifestyle choice.

If you have a lot of weight you need to lose, and find a calorie restricted intermittent fast works for you, then by all means use that to reduce weight. But for a lifestyle choice — for an eating schedule you can stick with for the rest of your life, and that you can count on to bring both health benefits and to keep off the weight you loss — choose a calorie unrestricted fasting regime. It is easy enough to live with, and the benefits are tremendous.

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.

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.

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.