The Ultimate Guide To Intermittent Fasting I – Feast vs. Famine


The Ultimate Guide to Intermittent Fasting 1 – Feast vs. Famine

Interested in Intermittent Fasting? Grab my book on it here: Feast.Fast.Fit. – Train Your Body to Torch Fat, Build Muscle, and Never Diet Again

Intermittent Fasting. What is this all about? Is it another dietary fad devised to lure you into buying a product or is it actually something useful? With the way the health and nutrition field is today, I’d expect you to be cautious. You are continuously bombarded with what to eat, what not to eat, what drugs you need or how sick you are. The bullshit ends here.

There is no perfect diet or training program. It doesn’t exist! Many roads lead to Rome. If it’s not for you, that’s ok. There are plenty of effective dietary methods. However, I believe given the health and longevity benefits alone, intermittent fasting is worth examining. This series of articles will arm you with the necessary information to understand, apply and benefit from intermittent fasting and under-eating protocols.



As the interest in Intermittent Fasting has picked up, so have the contradictions about what it truly is. There is a religious aspect to fasting that I will not cover here. Instead, I will focus on how you can use it for health and body composition goals.

In its true form, intermittent fasting is blending alternating periods of fasting (no food intake) with refeeding or feasting (food intake).  It is often described alongside calorie restriction, a dietary intervention where calories are reduced significantly (15-60%), while still maintaining sufficient micronutrient intake.

Recent research has demonstrated that the beneficial effects of caloric restriction, including improved glucose metabolism, successful brain aging, reduced inflammation and improvements in cardiovascular health, can be mimicked by intermittent fasting [1][2].

intermittent fasting and caloric restriction

The potential benefits all stem from the unique physiological changes that occur when the body undergoes limited energy intake. Later on, I will detail why I believe intermittent fasting is superior to caloric restriction alone.

However, not all fasts are created equal. There should be a plan and thought process behind the fasting period. Notice the word “plan?” It’s not forgetting to eat lunch and then eating dinner.  It’s not taking a few big breaths between eating a rack of ribs. It’s not skipping breakfast because coffee is easier to make. This is the biggest misconception that I see, even from respected coaches.

I emphasize the word plan because if you are fasting for 18 hours then you should know that the calories will be made up in your 6 hour feeding window.  Please do not confuse fasting with random meal skipping. Determine what you are trying to accomplish with your fasting period before you use it.

Lastly, Fasting does NOT mean starvation. You are fasting during your sleep, would you consider this to be starving? No. Being hungry does not equal starvation either. Starvation is a serious physiological condition where essential bodily processes begin to shut down due to a lack of nutrients. Nobody in their right mind advocates this.

The research I will present on fasting is intriguing and it will probably change the way you view nutrition; it certainly has for me.  I’ve written this series of articles to help dispel the inaccuracies, misunderstandings and fear that typically surround fasting.

This guide will introduce you to some common fasting protocols and how to tweak and use them for your specific goals; whether it is to gain weight, drop body fat, or just improve general health.

My First Fast

I still remember the first time I read about intermittent fasting. I credit DatBtrue, Martin Berkhan (, Mike T Nelson and Ori Hofmekler for “lighting the fire” so to speak. It just made sense to me. Reading their work really inspired me to dig even deeper.  What I found is a plethora of interesting research on the topic, much more than I had anticipated.  From there, I decided to give it a try.

Previously, I was a slave to 6-8 meals a day. I hate Tupperware, I hate cooking and I love eating at restaurants. So just imagine how miserable I was cooking a ton of meals and carrying it in ridiculous Tupperware everywhere. Eating was something that I loved, but now it felt like a job. I would literally watch the time and make sure I ate at specific intervals to “control my blood sugar” or “not go catabolic.”  Both of which are frivolous and ridiculous. Enter, my first fast.

I never, ever, missed breakfast. You know, the “most important meal of the day.” So when I woke up the day of my first fast and didn’t immediately eat, my body was in shock. The hunger set in immediately and I just felt a little “off.”  I also decided to train that morning and that’s when it got really interesting.

At first, I could feel the beginnings of low blood sugar. I was sweating more than usual and felt a bit lightheaded. About midway through my session I actually started to feel pretty good. I had a surge in energy and finished off the workout with no problems.

From there, I toyed around with fasting and different ways to implement it for a few years. I had a ton of success using it to drop body fat, improve my blood work, and most importantly, I learned a lot about food and my relationship with it.

Fasting literally released the dietary shackles that conventional nutrition wisdom had tied me down with. I finally felt I had control again.

I didn’t have to eat often to lower body fat.

I didn’t have to eat often to control blood sugar.

I didn’t have to eat often to “wake up” my metabolism.

I didn’t have to worry about the “dangers” of not eating for a few hours.

I got back to eating when I was hungry and listening to my body, not the latest-greatest diet secrets. For the psychological aspect alone, it was worth it. Suffice to say, this was enough for me to explore fasting even more.

Once I felt comfortable with my knowledge of intermittent fasting, I started to use it with clients who were open minded enough to try it. Just because I believe in fasting doesn’t mean that I feel it’s for everyone. I always ask clients if they have prior knowledge of fasting and whether or not they’d be open to trying it. My job isn’t to force my beliefs on them, it’s to get them results. However, I have yet to have a client who didn’t end up actually enjoying their fasts and the results as well.

I continue to study fasting and plenty of other dietary interventions, so that I can evolve with the research and further my knowledge. While it is a genuine interest of mine, it also allows me to offer unique and effective nutrition programs for my clients. But enough about me, let’s dig in.

Feast vs. Famine

“Feast or Famine” Road Sign with dramatic clouds and sky

As much as I enjoy fasting and find the research fascinating, a lot of the same benefits can be realized through stretches of caloric restriction and even glycogen depletion. Both methods share similarities and differences. I will cover this more in-depth later on.

To me, fasting or calorie restriction aren’t really “diets.” They are a part of our internal checks and balances. A fast or period of restriction can serve as a check against body fat or excess energy when overeating is occurring. Think of it like the brakes on your car. You wouldn’t want to hold your brake (not eating) the entire time, but you wouldn’t want to only have a gas pedal (eating), either.

In 2014, more than two-thirds of adults in the United States are overweight or obese. That is an alarmingly high number. We have the intelligence to print living human tissue with 3D printers yet we can’t seem to quite figure out the obesity epidemic. The issue, in my opinion, is multi-factorial. If you were to ask me the cause, I’d consider the following:

  • Psychological aspect
  • Humans predisposition to overeating
  • Constant availability and abundance of food
  • Lack of activity
  • Poor eating habits
  • Impaired metabolism and neuroendocrine signaling
  • Genetic and epigenetic factors
  • Environmental factors

Normally you hear blanket statements like, “carbohydrates make you fat,” or “It’s the processed foods that are making people gain body fat.” People want simple. While avoiding carbohydrates may limit food choices, it’s relatively mindless and therefore easy to follow. It’s much more difficult to acknowledge that there may not be a singular cause.  Instead, it is the interaction between one’s genetics, environment and psychology.

Where does intermittent fasting tie into this? I believe that our constant reliance on ingested energy and false belief that eating more frequently will speed the metabolism, is negatively effecting a lot of the things I mentioned above. Here’s why.

When I say that humans have a predisposition to overeat its simple evolution. Your body is focused on one thing – survival. From regulating energy levels to secreting hormones at specific intervals, the human body is in constant communication with itself to ensure that you acclimate to your current environment. The result is the ever-adapting, super-compensating and self-regulating species that we are.

Twenty thousand years ago your next meal was a mystery. Famine was the norm. Imagine going days with no food intake, how is that possible? It’s almost incomprehensible for modern day people to imagine this. Put simply, your body had one choice – adapt or die.

When we found a meal, our brain drove us to eat more than was needed at that specific moment. Your next meal may be days away, so in order to survive, you would overeat to make sure there was some readily available stored energy. We survived and continued to evolve because of our ability to cope with periods of feasting (eating) and fasting.

Imagine the relationship between feast and fast as a teeter-totter or yin and yang. Feasting ultimately results in growth and storage of new energy. Fasting balances this out by breaking down stored energy and “cleaning house” so to speak. The perfect relationship lies somewhere between the two. In today’s world, it’s a constant feast with very little fast periods. It’s obvious where that has gotten us.


If we are predisposed to overeat, are terribly inactive, and always making poor food choices, why would telling people to eat every 2-3 hours make any sense at all? It doesn’t and the rationale behind more frequent feedings doesn’t hold much weight as these studies clearly demonstrate [3,4,5,6]. The real disservice though, is the small amount of time that we spend in the fasted or underfed state.

Our body got very used to switching back and forth between our anabolic (feast) and catabolic (fast) processes. We didn’t know it at the time, but we were extremely metabolically flexible.

Finding The Balance

Balance between Energy intake and Energy expenditure

“The ability of an organism to survive during times of nutritional scarcity depends on its capacity to make appropriate metabolic adjustments.” [7]

The quote above is an important one when discussing fasting and metabolic flexibility. When food scarcity was the norm and the macronutrient content of meals was left to chance, we survived by being able to adapt; by using different fuel sources, slowing metabolism to conserve energy, regulating blood sugar, and secreting hormones to give us a burst of energy.

If our body couldn’t do these things we would not be here today. So when you mention fasting to someone and they say, “well what about your blood sugar,” please let them know that the human body is fully capable of maintaining blood sugar; but our reliance on carbohydrates and constant feedings have impaired our ability to do this.

Put simply, metabolic flexibility is our cells’ ability to switch between using glucose (sugar) or fat for energy. While we can also utilize other fuel sources for energy, like ketones, glucose and fat are our main energy suppliers.  Glucose is able to provide us with energy much quicker than fat, which is why it is our preferred fuel source for high intense activity.  Even though it’s a slower process, fat molecules still release more energy than glucose.

Metabolic flexibility can be estimated by finding one’s respiratory quotient. In plain terms this helps determine what fuel source you are burning for energy. Why does this matter? Because it can offer a lot of insight in figuring out how your metabolism is operating, are you a carb-burner or a fat-burner? Of course this will vary in terms of what type of exercise you are performing, what foods you are consuming, whether you are fasted or fed, etc. Do you know what else plays a role here? Whether you are lean or obese.

There’s an interesting study which tested the metabolic flexibility of muscle between obese and lean participants. In the fasted state, what they found was that glucose uptake and oxidation was normal or increased when compared to lean people [8]. Also, fat oxidation was lower and fat storage was higher in the obese compared to lean [8].

So, you eat a meal, what happens next? If you are having carbohydrates, a couple of things will happen. Blood glucose will increase which in turn should result in an insulin release to dispose of the glucose. If your metabolic flexibility is intact and functioning, your cells will begin to burn glucose instead of fat, thus keeping blood glucose controlled.

If you are metabolically inflexible, you will be unable to switch fuel source as easily and blood glucose will stay elevated and require more and more insulin.  Over time, this can potentially lead to excess fat storage and insulin resistance.

When a metabolically flexible person fasts, they are able to use fat as an energy source. However, when an inflexible person fasts, they aren’t quite as efficient at switching over.  Because they are so used to running on glucose, their body continues to try and burn glucose which forces the body to “demand” you provide it.

How do you know when this is happening? You will feel hungry, you will crave carbs or high sugar foods and you may start to feel hypoglycemic.  This is why fasting is difficult and sometimes counterproductive for obese people or those with poor glycemic control. This is what I experienced my first fasting day. All I could think about were bagels and I was highly irritable. Over time you’d like to teach your body to become more efficient at using fat for fuel thus reducing the hunger and irritability you experience.

Metabolic flexibility can also play a role in fuel usage during exercise. The more metabolically flexible you are, the more likely you’ll burn up stored fat, be able to train longer, and potentially produce more energy.

From the sounds of it, you want and need some metabolic flexibility, not only for body composition but health as well.  If lacking it, you are more susceptible to insulin resistance, type 2 diabetes, metabolic syndrome, obesity and mitochondrial dysfunction [9,10,11].  So what can you do if your metabolism is as flexible as a powerlifter trying to touch his toes? In my opinion based off the current research (which is always subject to change) I’d recommend:

– Lose weight and lower body fat
– Reduce overall carbohydrate intake
– Exercise (fed and fasted)
– Ease your way into some form of fasting/caloric restriction

In part II I will discuss the various forms of fasting, how it can improve health/fat loss/muscle accrual and more.

Part 2 – The Ultimate Guide To Intermittent Fasting II – Not All Fasts Are Created Equal

Part 3 – The Ultimate Guide To Intermittent Fasting – What Happens When You Fast?

Part 4 –

Ultimate Guide to Intermittent Fasting IV – What The Research Says

You might also be interested in this –

Intermittent Fasting and Cortisol


[1] Bronwen Martin, Mark P. Mattson, Stuard Maudsley.  “Caloric restriction and intermittent fasting: Two potential diets for successful brain aging.” Ageing Research Reviews, 2006.
[2] “Effect of Intermittent Fasting and Refeeding on Insulin Action in Healthy Men.” National Center for Biotechnology Information. U.S. National Library of Medicine, Dec. 2009. Web.
[3] Taylor MA, Garrow JS. “Compared with nibbling, neither gorging nor a morning fast affect short-term energy balance in obese patients in a chamber calorimeter.”  International Journal of Obesity and Related Metabolic Disorders, 2001.
[4] “Influence of the feeding frequency on nutrient utilization in man: consequences for energy metabolism.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d.
[5] Cameron, JD. “Increased meal frequency does not promote greater weight loss in subjects who were prescribed an 8-week equi-energetic energy-restricted diet.” Cambridge Journals Online. British Journal of Nutrition, 2010
[6] Bellisle, F., and R. McDevitt. “Meal frequency and energy balance.” National Center for Biotechnology Information. U.S. National Library of Medicine, 1997.
[7] , “Metabolic Adaptations to fasting and chronic caloric restriction in heart, muscle and liver do not include changes in AMPK activity.” American Journal of Physiology, 20004.


15 Responses to “The Ultimate Guide To Intermittent Fasting I – Feast vs. Famine”

  1. Filipe

    Hello Fred, I am crazy about your articles and have been reading every piece of information coming from you for the past weeks, but I cant acces your website through any computer, no matter the internet browser. I can only acces it from my smartphone. Could you please check if is there anything wrong going on?

    Also I am very interested about using IF for building muscle but cant find anything besides your article about the end of the cut and bilking diets, is there any other material you have written about it??

    Thanks a lot. Greeting from Brazil.

    • Fred

      Filipe, Thanks for the kind words. I’m glad you have found some of the articles to be helpful. I also appreciate you bringing up this issue as I have since gotten it looked at and it should be all taken care of. Please let me know if you are still having this problem but it should be good to go.

      In terms of using fasting for muscle gain specifically, I haven’t written too much on that yet. I will touch on it during this series of articles. If after these articles you still have questions about it then feel free to email me and I’ll do my best to help.


  2. Jim

    Good, well written article. I always appreciate your well-thought out positions. I look forward to reading more of your take on IF. Do you have any thoughts on Brad Pilon’s Eat Stop Eat approach?

    • Fred

      Jim, Thank you for reading, glad you liked it. To be honest, I don’t know much about his methods. If I recall, I believe he is a proponent of 24 hour fasts, right? Potentially leading up to 2x/week? If you can fill me in a little more on his protocol, I can give you a more useful answer.

      • Jim


        Yes he advocates a once or twice a week 24 hour fast, with focus on weekly caloric intake, rather than daily intake. He eschews the heavy meals that Berkhan advocates. but instead recommends moderately sized meals. They used to have lively discussions about it. I’ve tried Berkhan’s approach as well. I can’t say that either worked exceptionally well for my body comp, but like you, they freed me from the constraints of the constant feeding approach. John Berardi wrote an interesting ebook (free) about his n=1 experiments with fasting. I can send it to you if you’re interested.

        • Fred

          Jim, I also like people to focus on daily/weekly and even monthly caloric intake rather than just daily. So we agree there. In terms of large meals, I really don’t believe that smaller meals are more beneficial than large and I don’t think the research exactly disagrees there either. That usually comes down to the person. In my experience, smaller more frequent meals can very easily lead to overeating because there is simply more opportunity to mess up.

          In general, I feel that 24 hour fasts are too much for most people. Fasts ranging from 24-36+ hours are venturing more towards longevity/health benefits rather than physique. Of course, the goals of the person will come into play here too. I also believe that fasting every single day isn’t necessarily ideal either.

          Can they both work? Of course, but there’s always effective vs. optimal. I think the difference in my stance is that I view fasting as a tool in an overall protocol, not the protocol itself. With my clients I have times where total fasting hours are up and where they are down.

          I actually read Berardi’s book when it first came out, it was cool to see his transformation.

  3. Filipe

    Hello again, Fred. I have been following your advice for the last 4 weeks, since the first week after my bodybuilding show. My goal was (and still is) to keep myself lean, holding as much muscle as possible until I decide to gain weight again and prepare myself for the next show. What I have been doing is eating carbs in my weight training days (3 to 4 times a week) and bot eating them on my off days, when I also fast until lunch (about 12 hours after my last meal) . So far so good, I am keeping myself in good shape. There are 2 things that I still want to figure out, tough: when should I start eating on the off training/no carbs day (based on hunger?), and how much should I eat. As for the quantities, I am eating planned meals which I weight and consume every3 hours, just the way I do on the training days, what keeps me a slave of the Tupperwares, something I also want to get rid off – probably the answer to this is to plan the amount of calories that I want to consume on these days and simple divide it in as many or few portions as I want and feel confortable, right?
    Thank You.



  1.  Intermittent Fasting for Fat Loss, Longevity and Muscle Gain
  2.  What Happens When You Fast?
  3.  Interview with the King of Aesthetics - Frank Zane - Fred Duncan
  4.  Intermittent Fasting - What the Research Says
  5.  Meal Frequency, Nighttime Eating and "Not Eating Enough" - Fred Duncan Performance Training
  6.  Sports Nutrition to Maximize Athletic Performance
  7.  Intermittent Fasting Cliff Notes - Fred Duncan
  8.  Intermittent Fasting and Cortisol

Leave a Reply

Your email address will not be published. Required fields are marked *