Announcement

Collapse
No announcement yet.

Intermittent Fasting - A Primer ( Part 3 )

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Intermittent Fasting - A Primer ( Part 3 )

    After having been successfully fasting for 20 hours on a daily basis, as outlined in part 2, hopefully, everything is going as you intended, and you are seeing and feeling results. At the very least I hope that you are enjoying your liberation from having to eat in accordance with a schedule set by societal convention, rather than in accordance with your goals and priorities. Nevertheless, in spite of your successes, you may be wondering, can we do better?

    We have already established that an inter-meal interval of some 20 odd hours is not detrimental to health, quite the opposite, overall health and body composition seem to benefit from such an eating pattern. So, what would happen if we were to increase the interval between meals even further? How far is it prudent to go before we cross the dividing line between fasting and starvation? What would be the impact of doubling the inter-meal interval to 40h? We are actually rather fortunate with respect to answering the question, since every study performed on the effects of starvation on the human metabolism will have necessarily started out with a 40 hour fast. The only real complication will be due to the frequency of data collection, as many studies tend to focus their data collection on the latter phases. Let's see what we can find.

    The Impact of the 40 hour fast
    • Growth Hormone
      Growth hormone is very interesting due to the role that it plays with respect to nutrient availability as energy substrates. Ingesting both glucose and FFAs suppresses GH release, while certain amino acids tend to stimulate secretion. For the purposes of fasting, when exogenous sources of glucose and FFAs fall, GH levels rise to mobilize internal stores of both of these energy substrates. That is, GH promotes increased production of glucose by the liver, increases the breakdown of adipose fat tissue, as well as promoting nitrogen conservation ( protein tissues are spared ). As the bulk of growth hormone tends to be secreted at night, if there were any effect of fasting on GH, we would most likely like to include a fasted night time period in our approach. It turns out that a two day fast results in a five fold increase in the 24-h GH production rate. Essentially, what we're trying to do by extending the fast is to take advantage of the GH secretory burst that happens during the night, 24 hours or so into the fast, indicated with a red arrow in the graph below:
    • Free fatty acids
      Given that GH production rate increases five fold, we would expect, due to the lipolytic effects of the hormone, to see an increase in the circulating level of FFAs. As you can see from the table below, this is precisely what we observe. Around 32 hours into a fast, the FFA acid concentration in the blood is 3x higher than 8 hours into the fast ( ie an overnight / sleep fast ). 56 hours into the fast, that number has only increased by a further 20% suggesting that we are approaching a limit. The biggest bang for our buck seems therefore to be around 32+ hours. Given that we have all of these FFAs in the bloodstream 32 hours into a fast, it seems reasonable that we need to give the body a chance to oxidize the fats. We achieve this by keeping the fast going. It would undo all of our hard work were we to eat at this point and have the FFAs simply be reabsorbed by adipose tissue.


      The fact that FFA release peaks after two days of fasting is confirmed by the results in another study shown below. Due to the way that these authors labelled their graph, day two of the graph is represented by the line segment between the axis markers labelled "Day 2" and "Day 3".


      We should also pay close attention to the acetoacetate (AA) and beta hydroxybutyrate (BOH) on this graph. Both AA and BOH are ketone bodies produced by hepatic FFA oxidation, which means that, again, as expected, we're burning fat to provide an alternative energy substrate (ketones) for the brain and heart to use in lieu of glucose. Speaking of which, looking at the glucose levels on this graph, we see that during the first day of the fast, the liver can sustain nominal levels from its glycogen stores, but starting with the second day, we start a downward trend. This is significant, because at some point, the body will be forced to enter proteolysis, breaking down protein containing tissues, to provide inputs for gluconeogenesis thereby sacrificing lean mass for brain sustaining glucose. We wish to avoid this state, which will practically limit our fasting to a couple of days at most.

    • Cortisol
      We expect that Cortisol will trend upward over the course of a fast due to its proteolytic effects - increasing the breakdown of protein to make gluconeogenic substrates like alanine available for conversion to glucose. As the liver exhausts its supply of glycogen, generally within the first day of fasting, available blood glucose levels drop, and it becomes increasingly important to have the proteolytic effects of cortisol kick in. As expected, in the total fasting time graph above, we can see that Cortisol, over time, shows a slight upward trend, but, with respect to the levels at hours 8 and 36, they are roughly equal, suggesting that a fast of this duration is not a metabolic stress inducer, and does not require excessive conversion of protein from tissues as an energy substrate.
    • Insulin
      For the most part, there is not much to say here. From looking at our graph, we can see that over the course of a fast, insulin levels progressively drop. However, there is a very interesting rebound in insulin levels at the end of the fast, at 84 hours into the study, and here insulin levels rebound to levels seen 16 hours into the fast, but based solely on the anticipation of food!



    So, what does all of this mean?

    Fundamentally, if you are really concerned with body recomposition, that ultimately translates into burning adipose FFAs to reveal your underlying musculature. In terms of accelerated FFA oxidation, there is no substitute for a multi day fast. The first day of any fast serves to draw down liver glycogen stores. The subsequent days are spent oxidizing FFAs for energy. I would not advise going beyond 40 - 48 hours as you risk entering into the proteolytic zone.

    My personal experience, as well as that of others that have done this, is that the second day of a fast is generally easier than the first. I speculate that this is because insulin levels consistently drop as the fast progresses, and accordingly, perceived hunger drops as well. If you have habituated yourself to eating one meal per day in the evening, then a 40 hour fast actually entails merely skipping your one meal. For my part, I do this on a weekly basis.

    I think I will leave you with this for the time being. There is a lot to digest here, maybe too much.

    -PK
    Last edited by pklopp; 04-25-2011, 01:29 PM.
    My blog : cogitoergoedo.com

    Interested in Intermittent Fasting? This might help: part 1, part 2, part 3.

  • #2
    I did my 1st 40+hr fast last week. Couldn't believe how easy the last 15hrs was. When it was time to break the fast I wasn't even really hungry, could have gone on longer. After ready the above it's a good thin I didn't.
    http://kitoikitchen.blogspot.com/

    Comment


    • #3
      Thanks pklopp. Gonna give this a try. However, what would you suggest for training during this 40h fast? Should I skip training (just move it to another day), go lighter on the weights, lift normally and hope I don't bonk or just take some BCAAs if I do train?

      Just wondering.
      People too weak to follow their own dreams will always try to discourage others.

      Comment


      • #4
        This is awesome information. How would you go about breaking a 40-hour fast? Anything in particular in terms of calorie intake or macro composition?

        Comment


        • #5
          Wow! two minutes ago, I was wondering if you had posted part 3...

          Thank you so much.

          Definitely awesome! Have you considered an e-book?
          Ancestral Nutrition Coaching
          Pregnancy Nutrition Coaching
          Primal Pregnancy Nutrition Article

          Comment


          • #6
            pklopp, just wanted to say thank you for the great information. How do you feel about taking bcaas even when not training during the fast. Do you think it would mess up the normal process of fasting and how your body responds to it?

            Comment


            • #7
              if i did a 40hr fast my butt would break it with a BIG OL spoon or marrow.....nom nom
              Get on my Level
              http://malpaz.wordpress.com/

              Comment


              • #8
                Timely information. I am convinced that some sort of fasting protocol is important to maintaining good body composition and optimal health. I have never been obese or really heavy but I always want to be leaner than I am most of the time. I eat well, just too much and struggle not.

                Today I did a dinner to dinner 6pm to 5pm today fast and it was frankly much more pleasant than having to try and not eat. I ate a large dinner (maybe about 20% more than normal if that). I was able to do two light workouts with no issue and never sat down the entire day. I will continue this until I get to my desired weight (about 20 pounds). I will likely do a 2 day fast each week since this post points to some great potential benefits.

                Thanks for the information on the 40 hour fast.

                Comment


                • #9
                  Cool series of posts, thanks for the info.

                  We expect that Cortisol will trend upward over the course of a fast due to its proteolytic effects - increasing the breakdown of protein to make gluconeogenic substrates like alanine available for conversion to glucose. As the liver exhausts its supply of glycogen, generally within the first day of fasting, available blood glucose levels drop, and it becomes increasingly important to have the proteolytic effects of cortisol kick in. As expected, in the total fasting time graph above, we can see that Cortisol, over time, shows a slight upward trend, but, with respect to the levels at hours 8 and 36, they are roughly equal, suggesting that a fast of this duration is not a metabolic stress inducer, and does not require excessive conversion of protein from tissues as an energy substrate.
                  You say that the slight upward trend in cortisol is not too proteolytic, but it is somewhat so. So are GH and cortisol kind of antagonistic to each other? In that the former encourages liver glucose production and the use of stored adipose tissue. Or is it that cortisol can encourage gluconeogenesis so that GH can then stimulate the liver to make glucose from those substrates?

                  Is the slight increase in cortisol anything to be worried about for those concerned about the cortisol-belly fat connection? Or, if the abdomen is the place of stored subcutaneous fat, would the benefits of longer fasts outweigh the potential negatives?

                  Comment


                  • #10
                    A number of you have asked about how to go about breaking the fast, whether it mattered, and if so, what macronutrients, ratios, etc. would be advisable?

                    The quick and confusing answer is that it matters and it doesn't.

                    The reason it matters is that unless you have been eating this way for quite some time, there will be a period of adjustment during which if you eat particularly rich foods to break your fast, these may cause some gastric upset. For me, the only time that I experienced problems was when I broke my fast with a particularly fatty meal. I overdosed on cheese ... once ... haven't done it since. I think eggs make a pretty good breakfast and break fast. High in protein, high in good fats, easy to prepare, quite gentle on the stomach. I always have some vegetables, mostly salads Personally, I don't particularly care for carbohydrates, and I don't seek them out when breaking my fast, but you can probably get away with them here.

                    The reason it doesn't matter is that your body needs food, and will be plenty happy to get it irrespective of its ultimate form. From an evolutionary perspective, an organism that is living in an energy uncertain environment ( hence the fast, due to irregular availability of food ) but then requires a specific nutritional makeup for any food that it should happen to find is one dead organism. This is tantamount to the man crawling through the desert, finding an oasis, dragging himself up to it only to ask "Do you have any sparkling water?" We cannot rule out such potential behaviour, but we can predict that it runs contrary to the survival of the organism.

                    I understand that the underlying motivation behind the question is an attempt to wring every last ounce of benefit from this process. This is commendable, but I think it is certainly a case of premature optimization. Get the basics down first, then tweak for that final 1%.

                    -PK
                    My blog : cogitoergoedo.com

                    Interested in Intermittent Fasting? This might help: part 1, part 2, part 3.

                    Comment


                    • #11
                      Don't get caught up by paralysis of analysis. I always fall back onto the fact that what "we" know is a fraction of won't we don't know.
                      No eating sometimes is much more natural than eating all of the time. Evidence points to fasting and calorie restriction appears to increase lifespan and my guess is quality of life. Everything else is just a bit of noise that you can ignore.

                      Comment


                      • #12
                        Originally posted by imasin View Post
                        Cool series of posts, thanks for the info.

                        You say that the slight upward trend in cortisol is not too proteolytic, but it is somewhat so. So are GH and cortisol kind of antagonistic to each other? In that the former encourages liver glucose production and the use of stored adipose tissue. Or is it that cortisol can encourage gluconeogenesis so that GH can then stimulate the liver to make glucose from those substrates?

                        Is the slight increase in cortisol anything to be worried about for those concerned about the cortisol-belly fat connection? Or, if the abdomen is the place of stored subcutaneous fat, would the benefits of longer fasts outweigh the potential negatives?
                        You have to be very careful with language because to define something is to limit it. That is, the linguistic framework we build around something restricts our ability to think about it. A perfect example of this is the notion of "antagonistic" hormones. Antagonism, for most of us, suggests that these hormones are at cross purposes with each other. But that is not what we mean at all. Rather, what we are trying to say is that, in general, when we sample cortisol and GH in an individual, we observe that they are inversely correlated, so when levels of one are high, the levels of the other are low. But this is a much weaker statement than "antagonism", because it allows for the existence of specific circumstances when we may observe high concentrations of both, like say, during prolonged energy deprivation.

                        When the body detects that there is an energy shortfall, it will do several things:
                        • It will attempt to reduce the amount of energy it discretionarily expends, which will necessarily impact thyroid hormones, and ultimately, thermogenesis, which is quite expensive in terms of energy consumed. So, during a prolonged fast, expect cold hands and feet, and better make sure you have a heavier blanket.
                        • It will attempt to conserve blood glucose and to do this it needs all tissues that do not require glucose to stop trying absorb it from the blood. Luckily, GH inhibits the use of glucose by the muscle. But that leaves us in the position of having lost a source of energy for muscular activity. Doubly luckily, GH is lipolytic which increases FFA availability as an alternative energy substrate for the muscles. But what about those tissues that cannot use FFAs and resulting ketones for energy? For those tissues:
                        • It will attempt to produce new glucose via gluconeogenesis. In this case, the inputs to this process are amino acids, so the body will need to find a supplier for these that does not require food. Luckily, we carry large pools of amino acids in all of our proteinaceous tissues. The trick is to liberate them, and this we achieve via the action of cortisol. So, during the course of a fast, cortisol levels increase to ensure that we can rely on gluconeogenesis as a source of glucose.


                        All of this is to say that actually, GH and cortisol are acting synergistically to provide the body with adequate energy from internal sources.

                        The cortisol belly fat connection is a marketing ploy to attempt to sell you some particular pharmaceutical or herbal cocktail that presumes to fix it. This is very similar to what happened with cellulite, which is nothing more than subcutaneous fat, but if I can sell you the disease, cellulite, then I can sell you the cures: anti-cellulite creams, exercise programs, and magic bracelets.

                        I am extremely fond of my proteinaceous tissues, especially my muscles. If there were some way to direct my cortisol to take some protein out of my nose, to make it more petite and button like, that would be great. Unfortunately, it doesn't work like that, so I am extremely wary of pushing my system into a situation where it will start to cannibalize hard earned muscle to keep my silly brain alive. So now, we have a tradeoff. How much muscle am I willing to give up for less subcutaneous fat? Not very much, so I advocate keeping fasting in the range of 40 hours in accordance with my priorities. If you really want to burn more fat, fast longer, realizing that you will be sacrificing more muscle tissue along the way. I do not recommend that you do this, but, it is ultimately your reality, and your decision.

                        -PK
                        My blog : cogitoergoedo.com

                        Interested in Intermittent Fasting? This might help: part 1, part 2, part 3.

                        Comment


                        • #13
                          I'm currently on a 22 hour fast (attempting it) as I usually just do a 16/8 feed window with lunch and dinner. And a couple of things popped my mind.

                          Both in a 24 hour fast (or more) and in the 16/8 - 2 meals a day IF, if I want to consume a decent amount of carbs to have a good day and good restful night, where should I have more of them, in lunch or dinner? Maybe lunch have a couple of sweet potatoes, salad and veggies (or other carbs) and at night just meat/fish/eggs and a salad and cucumber?

                          Comment


                          • #14
                            Thanks for all of this pklopp.

                            I am past 32 hours and aiming for 40 before I break the fast. The hardest part was at about 20-22 hours, but I drank a lot of water and fell asleep very fast. Not sure if that had anything to do with the fast or not, but it is nice since I don't do it very often.
                            Woke up this morning and feel great. Not hungry at all and going the last 8 hours or so should be a breeze.
                            I did not train yesterday, I have pushed it off until today where at lunch I will go split a chord of wood while drinking a protein shake. After, I plan on having 1.5lbs of beef heart, avocado and a salad. In case anyone cares. LOL.
                            People too weak to follow their own dreams will always try to discourage others.

                            Comment


                            • #15
                              I used to do a once-a-week 40 hour fast way back when I found MDA through Art Devany's site. Now I am probably mature enough dietwise to do it again successfully, so I'll give it a shot.
                              You lousy kids! Get off my savannah!

                              Comment

                              Working...
                              X