Intermittent fasting appears to be gaining momentum, both from the research community and individuals experimenting with the process. It is an incredibly exciting topic, as a simple intervention like compressing one's period for eating in a given day and/or eating every other day may provide benefits ranging from life extension to amelioration of disease states such as Huntington’s, Parkinson’s and Alzheimer’s. That is simply amazing. We will continue to bring you information from pertinent research and highlight reader submissions detailing how they make IF work and what their experiences are.

First let's look at a literature review and then submissions from Scotty Hagnas of CrossFit Portland and Kurtis Bowler of Rainier CrossFit.

I stumbled across the site www.nutritionandmetabolism.com and discovered some real gems. The offerings are not extensive as of yet but appear to be of excellent quality and pertinent to many of the questions we are interested in. This paper was particularly interesting as it lends validity to some of the assumptions we have made regarding intermittent fasting, specifically the potent anabolic state inherent in IF and the potential of relatively short fasts delivering impressive metabolic results.

The paper is a review of very low carb diets (VLCD) and discusses not only the benefits and results of VLCDs, but suggests some of the mechanisms at work. These mechanisms look eerily similar to those seen in IF and are why I suspect a low-ish carb diet AND training while hungry will augment the effects of IF.

The Anssi paper lists four possible mechanisms for the protein sparing characteristics of a low carb diet. It is perhaps important to note that this can be broadly applied to the term “ketogenic diet.” Prior to my exposure to IF, I thought ketosis could only happen in carbohydrate scarcity. This is obviously not the case as one main characteristic of IF is the production of ketone bodies despite an almost 70% carbohydrate diet.


Mechanisms

The first mechanism proposed in the paper is Adrenergic stimulation which is interchangeable with a term I have used previously, “adrenal cortical modulation”. Adrenergic stimulation fits nicely with what we know about improvements in health via modulation of the stress response in CRAN and IF. In essence, a VLCD increases circulating levels of epinephrine (adrenaline) and this appears to have a potent protein sparing effect. Some of our readers have described a decreased need/tolerance for caffeine while following IF and this is further validation that the brief 15-18 hour fasts are favorably altering the adrenal cortical response.

The second mechanism concerns ketone production, specifically β-hydroxybutyrate (BHB). BHB/ketosis has effects on the mechanism mentioned above (modulation of the adrenergic response) AND ketosis has several interrelated effects on protein accretion. The first effect involves the uptake of the branched chain amino acid Leucine. Leucine is an indicator of anabolism in skeletal muscle; however, under chronically stressful conditions and/or hypoglycemia, the branched chain amino acids are utilized in the production of glucose via gluconeogenesis.

It is important to note that in the hyperinsulinemic state, these protein-sparing mechanisms are NOT at work. In fact the hyperinsulinemic state is worse than overt starvation with regards to lean muscle maintenance… at least up to a point! In actual starvation and basic isocaloric ketosis, there are many mechanisms in place to prevent muscle loss. Not so with hyperinsulinemia.

Many studies have shown the state of ketosis to be anabolic (ie. people GAIN muscle) despite being in a hypo-caloric state. No, these are not typically trained individuals and one is not going to add huge amounts of muscle via this process, but it is interesting that as metabolic derangement is put right (think about the average chubby Westerner), even under a scenario of negative calorie intake, the natural state for the human body is to be lean and muscular. There might even be hope for the sarcopenic “men” of CrossFit NorCal!!

Ok… I have to digress a moment here. Leucine metabolism is REALLY cool and is a central player in leptin release and protein accretion in both muscle and adipose tissue. This paper (http://ajpendo.physiology.org/cgi/reprint/285/4/E854) gets DEEP on that topic. The take home message is that HOW leucine is metabolized determines many downstream hormonal and gene expression events that determine, at least in part, body fat and lean muscle levels.

The authors miss the boat on the third proposed mechanism. They focus on growth hormone (hGH) levels, which do not increase on a VLCD, but they do note that IGF-mRNA increases by a factor of two! The authors do not mention whether there is an increase in IGF-1 receptors or if the normal number of receptors are more sensitive, but it is an interesting and important point.

For you people who have a real life, friends, and are not pathetic shells of humanity (like me), it may not be overtly clear what increased IGF-1 mRNA is: increased IGF-1 mRNA expression means the effects of IGF-1 (growth, repair) are increased, in this case by a factor of two. The authors ascribe this increase in gene expression to increased dietary protein intake*. I think they are missing something relating to ketosis itself as we see both an increased expression of IGF-1 mRNA in simple ketosis and an outright increase in circulating IGF-1 in intermittent fasting. What this means is a low carb diet (say cyclical low carb or perhaps training on an empty stomach) should facilitate and/or enhance the effects of intermittent fasting EVEN WHEN THE FASTS ARE RELATIVELY BRIEF, say fifteen hours.

How low is low carb? It looks like Zone parameters and below are working. Perhaps higher will also work, but so much of this is still theoretical it is difficult to say. Remember that the IF studies conducted thus far have involved a nearly 70% carb diet for the critters in the studies, but then again, the fasting periods are a full 24 hours. What I hope to do is get some mileage out of a lower carb approach and smart exercise.


Intermittent Fasting Round Up

The one or two of you not using this article as a cure for insomnia may be wondering what all this means. My interpretation is that the normal default mode for humans appears to be a state of anabolism, growth and repair via a complex interplay of nutrient intake, exercise and other lifestyle factors. Some might say intermittent fasting, CrossFit and friends.

For just a little more nerdy-let's-beat-this-to-death-ness, let's consider that most anabolic processes involve inputs by two interrelated axes: the hGH/IGF axis and the hGh/testosterone axis. It is quite clear that in the IF state the hGH/IGF axis is dramatically improved via increased IGF, while the hGH/testosterone axis is at least maintained and is possibly improved so long as caloric content is sufficient. This is essentially a shift in the anabolic/catabolic axis towards a NET anabolism; however, this is achieved with elements or periods typified by catabolism (ketosis).

Here are a few other things to consider. First, the practice of multiple small meals may be an effective way to push muscle mass to the absolute limit—I’m thinking 300lb bodybuilder types. But it is interesting that many people who have had problems gaining muscle on the multiple small meal protocol, regardless of macronutrient content (Zone, cyclic low carb, high carb low fat…), have been experiencing success on intermittent fasting if they get their caloric content to adequate levels. I suspect several factors are at work here; among them is an optimization of the anabolic state, yet with remarkably LOW insulin levels. The post workout carb load, especially amidst five or six other meals, does not appear to work for everyone, especially people who may have questionable insulin sensitivity. I think the people who have been succeeding on the standard bodybuilding approach have excellent hormonal responses, but that will only last so long. This IF approach may be the ticket to greater muscle mass and performance for the squidlier folks among us. That test is in progress and we will keep you updated!

*(This is actually mechanism 4 of the paper but not really worth delving into. Increasing protein availability enhances anabolism—not too earth shaking!)


Reader Intermittent Fasting Experiences

Scotty’s piece details his meal times and approximate caloric content for several days while Kurtis describes his experience with an alternate day IF schedule. I think you will find both contributions very interesting.

Scotty Hagnas

I think it is worth noting that many of Scott’s days involve a relatively short 15-hour fast, yet Scott has seen improvement across all performance parameters. He has also gained 8lbs of lean body mass in the past year and this on a guy who, like me, finds it very hard to put on any muscle without also adding fat.

Mealtimes - March 2006

Times in parentheses are the duration of the fast-Ed.

3/1 - 13:40, 15:30, 1710, 18:30 extra protein today
3/2 - 10:30, 12:00, 13:30, 15:45 (16)
3/3 - 6:15, 9:00, 13:30, 16:00 (15) very light meals/snacks today
3/4 - 6:30, 9:40, 14:00, 17:00, 19:00 (14.5) big eating day
3/5 - 11:00, 12:15, 14:30, 18:00 (16) extra food
3/6 - 9:30, 17:00 (17.5) first light, last big meal
3/7 - 8:00, 11:00, 13:30, 18:15, 22:15 (14) extra food
3/8 - 11:30, 13:50, 16:30 (13) little extra
3/9 - 13:30, 18:30 (21) light meals
3/10 - 6:15, 9:15, 12:30, 15:30 (12) extra
3/11 - 6:15, 9:15, 13:00, 18:00, 17:30 (15) extra
3/12 - 9:00, 11:45, 16:30, 18:00 (16)
3/13 - 8:30, 11:30, 13:30, 18:20 (14.5) extra
3/14 - 8:00, 14:30, 19:00 (14)v. light early, med lunch, big pm
3/15 - 9:30, 11:30, 15:30, 18:15 (14.5)
3/16 - 9:30, 11:30, 14:30, 21:00 (15)
3/17 - 8:00, 12:00, 19:00 (11) v. light early, med pm meal
3/18 - 8:30, 13:00, 21:00 (13.5) light protein
3/19 - 11:00, 16:00, 18:30 (14) light protein
3/20 - 11:00, 13:30, 16:00, 18:30 (16.5) extra cals, lots protein
3/21 - 9:45, 13:30, 19:30 (15)
3/22 - 10:30, 19:30, 21:10 (14) large meals
3/23 - 9:30, 12:30, 17:35 (12) very light day (7 P, 4 C) Zone Blocks
3/24 - 7:20, 12:45, 18:10-20:40 (14) big pm meal
3/25 - 7:15, 12:35, 18:40-20:20 (10.5) light early, big pm
3/26 - 6:45, 12:35, 17:30 (10.5) light early, big pm
3/27 - 8:00, 12:15, 16:10, 17:10 (14.5) first 2 light, last 2 bigger
3/28 - 9:30, 12:15, 14;00, 18:30 (16)
3/29 - 8:30, 10:00, 14:30, 16:30 (14)
3/30 - 9:00, 10:30, 15:45, 18:00 (16.5)
3/31 - 9:00, 12:20, 15:00 (15) light day

"On days where there is an early breakfast, it isn't really early, as these are the days that I get up at 2 am. My always-changing schedule really helps randomize mealtimes."


Kurtis Bowler

A few things jump out at me here. Weight loss, particularly from the abdomen, is a remarkable indicator of improved insulin function and decreased risk of type II diabetes, heart disease and actually ALL of the Syndrome X complications of hyperinsulinemia. The second point is improvement in strength while maintaining metabolic conditioning. That appears to be consistent with the experiences of others following IF. Perhaps most importantly it is a nutrition option that compliments the very busy schedule of a police officer/strength coach/father/husband. The Zone obviously has merit and application, however its static nature has never appealed to me on either an intuitive or practical level. People find it hard to implement and it has certainly not cornered the market with regards to optimized performance, health and longevity.

"Down 13lbs which is a good thing. Seems to be mostly from the mid-section. Energy levels are great. Better on the fasting days. I'm pretty good about quality on my eat days, but could do better here. Higher protein and fat than the Zone and lower carb. Strength is better than it's ever been. I hit a 500 and 505lb Deadlift on two consecutive Saturdays. Old PR was 445 a couple months ago. Times on the girls are holding steady and my guess is they will start dropping as my body adapts to eating this way. Weekends seem to be difficult to not eat, so I've been eating Saturday, Sunday, Tuesday, Thursday and fasting Monday, Wednesday, and Friday. My fasts go from about noon to noon. I'll change it up and fast on weekends too if we don't have anything going on.

"The weighing and measuring and timing of the Zone just don't work for me and my schedule. This does, and if it keeps me around for my wife and kids a few extra years all-the better."