Learning to fast

I’m writing this post the week before Thanksgiving, to give you something to think about as you are polishing off that last piece of pie….

One of the most common reactions I get to my advice to try intermittent fasting is:  I could never do that!

Like the Jackson Browne song “Running on Empty,” the word “fasting” often conjures up dire images of starvation and energy deprivation.  Many of you reading this post may have experienced strong hunger pangs, headaches, tiredness, sweating and even shaking or wooziness when going without eating for even part of a day, much less a whole day.  So it is natural to extrapolate such experiences into the thought that going without food for a day, or even several hours, would invariably lead to uncomfortable or even dangerous hypoglycermic symptoms. That, together with the negative image of fasting as something unhealthy or associated with eating disorders, leaves most people pale at the thought of even attempting a short fast.

But I tell you, if you don’t try fasting you are missing out on an enjoyable, incredibly energizing experience that will put you in control of your eating and improve your health, your energy and your outlook.  Many people, myself included, have learned to fast for up to a day or even longer, on a regular basis and without negative repurcussions. Done correctly, short-term fasting is not dangerous, it’s actually health-promoting and greatly helps to retrain your appetite.  If you need to lose weight, the fast helps both in reducing basal insulin and retraining your appetite to be smaller. I’ve written about the benefits of intermittent fasting extensively on this site. Many of the Diet Links listed in the right-hand panel, such as fast-5 and Eat-Stop-Eat, amply document the safety and health benefits of fasting, dispelling the myths about “starvation mode”, slowing of metabolism,  and loss of lean muscle mass.  So I won’t reiterate here the voluminous evidence supporting the benefits of intermittent fasting.  Our bodies are designed to last many days with out food, without great discomfort, and in fact it is beneficial to our health to forgo food periodically. But many of you are asking: Am I really up to this?  How do I get started?

To clarify, by intermittent fasting (IF), I mean forgoing eating for at least 12-20 hours in a day, at least one or two days each week. For many of us, it is a daily practice. Water and unsweetened, non-caloric beverages are allowed, but I exclude “juice fasting” or any solid snacks from true fasting. Others have written about the virtues of juice fasts for “detox” or “cleansing”, but IF has a different purpose, namely insulin reduction, appetite reduction, and mental clarity and focus.

Tips for getting started. So this post is not about the benefits of intermittent fasting, but rather about how to get started with it.  I’m basing this largely on my own personal experience, combined with what I’ve learned about what has worked for others. Fasting is not that hard or unpleasant to do. The reality is that, like skydiving, the contemplation of it is probably far worse than the experience.  You will experience some periods of discomfort, but you may be surprised at how great you’ll feel most of the time you are fasting, especially once you are past the first few hours.  People on low carbohydrate diets often (but not always) experience the pleasurable energy that comes with ketosis; I’ve found that the ketosis of fasting is deeper, and more reliable that that from low carb.  Several people who experience brain fog on low carb  find fasting to provide greater clarity and energy.

Here are 7 practical suggestions to help you get through the transition:

1. Start with a mini-fast. How long do you go between meals without eating? Two hours? Five hours? Start there and try to increase it by a few hours. The easiest way to start is to cut out eating anything between dinner and bedtime. Then go to cutting out afternoon snacks 2 or 3 days a week. And increase from there in increments. Of all my suggestions, I think this is the most important. It’s one of the core principles of using Hormetism to improve your strength and resilience in any challenging endeavor. You have to walk before you can run.

A very common mistake that many people make when embarking on fasting is to go straightaway from a typical pattern of 3 meals per day with snacks, to a day-long fast.  That’s a terrible idea, and yet it forms the main reason that so many people reject fasting as impractical or unhealthful.  I’ll repeat here the comments I made in an earlier post on Calorie restriction and hormesis about a researcher’s conclusions in a 2006 study of calorie restriction in mice, in the journal Biogerontology:

Calorie restriction is doomed to fail, and will make people miserable in the process of attempting it,” said Dr. Jay Phelan, an evolutionary biologist at the University of California, Los Angeles, and a co-author of the paper. “We do see benefits, but not an increase in life span.” Mice who must scratch for food for a couple of years would be analogous, in terms of natural selection, to humans who must survive 20-year famines, Dr. Phelan said. But nature seldom demands that humans endure such conditions. Besides, he added, there is virtually no chance Americans will adopt such a severe menu plan in great numbers. “Have you ever tried to go without food for a day?” Dr. Phelan asked. “I did it once, because I was curious about what the mice in my lab experienced, and I couldn’t even function at the end of the day.

It’s not surprising that Dr. Phelan’s personal “one day experiment” failed and that he “couldn’t function” after suddenly downshifting gears so rapidly. As anyone who has taken the time to research calorie reduction or intermittent fasting realizes, a dietary change of this sort should be approached gradually, allowing time for deconditioning of previous dietary habits and hormonal responses. These changes typically take weeks or longer to become comfortable. But that does not mean that a reduced calorie diet is “extreme”. By historical standards, it would be more accurate to characterize the typical hypercaloric American diet as extreme.

2.  Schedule your fasts. Intermittent fasting works best when you are in control of the timing.  I like being able to spontaneously decide when I’ll start my next fast and I plan exactly when I’ll break the fast and eat.  That really frees me from thinking about food and making choices, because I know that at 4 p.m. Friday or noon Sunday I’ll have my next meal. Associating the start and stop of a planned fast with definite events or times of day takes advantage of the well-known behavioral principle of “putting on cue”.  For a fuller explanation, check out the work of Karen Pryor, the renowned animal behaviorist and dolphin trainer.  I’ve also written about this on the Psychology page of this blog.

3. Cheat using high fat “training snacks”. If you’re having trouble fasting, it is likely that you are lacking the ability to readily shift to fat burning and ketosis.  When you are fasting, after initially depleting your glycogen stores, you will be literally “living off your fat”, as well as fat byproducts like ketones.  To do that, you’ll need to get your insulin level very low and upregulate your catabolic hormones and enzymes: glucagon, adrenaline and hormone sensitive lipase.  But if you are used to eating 3 or more meals and snacking frequently, then you are not used to metabolizing your own fat stores, and you have difficulty shifting quickly from energy storage (anabolism) to energy release (catabolism) .  You literally have weeks of “meals” stored beneath your skin and within your abdomen.  You just can’t access them.  It’s literally like having a locked pantry on your body, so when you get hungry you have to eat food supplied externally, instead of what is already within you.

So train yourself to burn fat by eating pure fat or oil!  The easiest way to train your body to get it used to burning fat, is to “jump start” it with a small high-fat “training snack”.   You don’t need much to get started: 5 to 10 grams of fat is plenty.  Don’t worry, this is not a “high fat diet”, it serves only to provide some satiety and let your metabolism get used to fat burning. The amount of fat you’ll snack on is trivial compared to your overall weekly diet, and you’ll go back to your “normal” diet after the fast. The best approach is to wait until you would normally have a meal or snack and substitute the high fat training snack.  This will tend to suppress your appetite for at least a few hours.  If you start to get hungry again, take another training snack — but wait at least 3-4 hours between these snacks. The training snacks must be virtually free of any carbohydrates or protein and must be small.  Good examples include:




  • “Carbless cream soda”. Pour a few tablespoons of heavy whipping cream into a glass (check to make sure it has less than 1 gram carbs) over ice cubes and add sparkling water or herbal tea.
  • “Platinum” tea or coffee. To an unsweetened cup of hot tea or coffee, add a tablespoon or two of heavy whipping cream or coconut oil.  The heavy cream has the advantage of easily blending with the tea or coffee, but some people find the coconut oil to be more energizing.  It comes as a solid but readily melts in the hot beverage; it tends leave some oily droplets on the surface because it does not emulsify as well as cream, but most people have no problem with that.  It is important not to add any sweeteners; even artificial sweeteners will tend to psychologically induce a conditioned preprandial insulin response (See Diet page).
  • Macademia nuts.  These are high in fat with very few carbs.  Eat no more than a half dozen.
  • A small piece of cheese. This is a great training snack, but keep it to one or two small slices of cheese.
  • A tablespoon of oil. It may not sound very palatable, but a spoonful or two of extra light olive oil or other vegetable oil can be a great appetite suppressant and kick you into fat burning mode rather effortlessly. The oil works best if flavorless, or if you pinch your nose to avoid tasting it before rinsing.  This is the basis for the popular Shangri-La Diet of Seth Roberts. Roberts attributes the effect to breaking the connection between flavor and calories.  I propose an alternative explanation in my post on Flavor Control Diets.  and also in a long discussion thread on the Shangri-la Diet forum. In any case, flavorless or not, a small dose of oil is a very effective “bridge” to fasting.

4.  Savor flavored calorie-free beverages. To satisfy your need for flavor, enjoy herb teas and black coffee.  Decaf is preferable, but if you have a caffeine habit, go with it for now.  Don’t add any sugar or artificial sweeteners, since these can induce an insulin response that shuts down fat burning. Flavored beverages are a great boon to fasting because they satisfy the urge for flavor and provide some pleasure that can be a big help.

5.  Smell something aromatic while fasting. This is an old aromatherapy trick to turn off your appetite, but it has a scientific basis.  A strong aroma from herbs, spices, flowers or perfumes can rapidly dampen a craving by saturating the cephalic phase insulin response, as explained in my post on Flavor control diets — but you must not eat within 30 minutes after smelling. It is also useful to repeat the smelling frequently and cycle between very different aromas. This has been exploited in devices such as the SlimScents odor inhaler, but a few minutes with your spice rack, perfume bottles or flower garden may do the trick.  The good news is that the effect is long lasting and will permanently decondition your cravings.  Try it!

6.  Drink water frequently. This is an old standby and may seem boring compared to the above two suggestions.  But it works well in two ways: it tends to suppress hunger, and it keeps you hydrated. Keep in mind that the effect is often delayed, so wait 15-30 minutes after drinking the water before you pass judgement on it.

7.  Exercise briefly when hungry or tired. This is one of the more surprising ways to fight cravings, tiredness, mental fog, or borderline hypoglycemia. It may seem counterintuive to expend energy just at the point you are feeling hungry or tired. But it works incredibly well! The key is to do it at the first sign of a cranky or tired feeling, and you’ll head off it off at the pass.  By “exercise” I don’t necessarily mean going to the gym — unless you are used to that. Walking around for 5-15 minutes at a brisk pace is good enough, particularly if you can elevate your heart rate a bit. If you have been fasting, walking or other brief exercise will stimulate your liver to release glucose and free fatty acids, giving you an energy boost. It really is just about as good as eating a meal, for providing energy, and it has the benefit of providing a more sustained form of energy.  You’ll find that “after lunch” meetings are less soporific.

Getting out for a lunch time walk is an excellent alternative to eating lunch.  It gets you away from the kitchen or cafeteria, changes the scene and restores energy.   I probably eat only two lunches a week at work; the other days I go walking either outside or inside, depending on the weather.  Make it social and enlist a friend or start a small walking group – it is just as easy to converse while walking as while eating at a table.

When you get more experienced with fasting, the addition of extended, more intense exercise is very energizing and beneficial. With lower basal insulin levels and upregulated catabolic hormones and enzymes, you’ll find that a long run or workout with weights provides lasting energy and suppresses your appetite. Eating before or after the workout ruins the benefits. Wait at least several hours after the workout before breaking the fast. This may seem paradoxical, as it is virtually the opposite of what many experience who are not used to fasting.  But I have found it to be my experience.  For those interested in fasted workouts, checkout Martin Berkhan’s Leangains blog, as well as a recent article in Runner’s World on the benefits of glycogen-depleted exercise for greatly increasing your endurance; it appears to be a great strategy for learning to burn fat and weaning yourself off carb dependence,

A final word. The above approach, which emphasizes gradualism, should give your metabolism time to adapt.  For most people, this is enough to avoid any health issues with hypoglycemia or diabetic complications.  In fact, Lee Shurie cured his diabetes, normalized his blood sugar, and increased his energy level by carefully monitoring his blood glucose and gradually transitioning to intermittent fasting.  He found that all the traditional advice to eat low glycemic foods and exercise was insufficient to normal his blood glucose. Eventually, by delaying meal time and allowing his blood glucose to drop into the normal range, he found himself eating only at dinner time, and all the happier for it.  So transition to IF gradually. However, if you have any concerns, stop the fast and eat.  Consult with your physician if you have concerns.  Otherwise, check out the discussion of Intermittent fasting on the Getting Stronger Discussion Forum, to read others’ experiences.

Happy Thanksgiving!


  1. George

    I hesitated fasting because I’ve experienced hypoglycemic type shaking when I skip meals. But this post has given me some encouragement. I tried your suggestion of a few macademia nuts or — love it– the cream soda and it got me through the entire afternoon. I’m feeling less cravings the last few days — even Thanksgiving! I think I can do this. Thanks for the post

    • Nicolas Martinez

      This post has been a tremendous help. Especially if you have no idea how to start fast. Here is some more info to help: http://bit.ly/1qPhNqw

      • s

        The above comment by Nicolas Martinez is spa (m)

  2. Daan van den Bergh

    Hi Todd,

    I really love your blog’s topic. It’s kept me reading from the start.

    But I have a question about the main topic, Hormesis. And this post seemed the most relevant to post it on.

    You’re fasting to induce small doses of stress, right? To increase your physical and mental strength, am I right?

    So does it only work when stress is created willingly? Such as fasting. Or do people that are regularly exposed to stressful situations, e.g. a person that is repeatedly abused, also create this state of physique/mind?

    • Todd


      Your question is one of the most interesting ones I’ve read! It’s something I’ve thought about but for which I don’t have any definitive supporting research. My best answer is: it depends. Certain types of hormetic stress clearly work without any voluntary element. For example, there is no voluntary element involved in radiation hormesis, which has been validated based on retrospective analyses of people living at a certain distance outside of the Hiroshima bomb blast, or occupants of buildings containing low level radioactive steel or radon, or animal studies. The same is probably true of various types of chemical hormesis and other stressors of which we are not consciously aware.

      However, it seems to me that “psychological hormesis”, where you expose yourself to cold showers, intense physical activity, fasting, or other unpleasant activities work better when chosen voluntarily. There is certainly a physical element in each of these activities (such as thermogenesis from cold showers or autophagy from fasting) that will take place even if involuntary, but I think that if these activities are forced and sustained, there could easily be negative stress that counteracts the benefits, for example via stress hormones such as cortisol, and also aversive conditioning to repulsion, fear and perhaps even terror. I have no doubt that physical, sexual or psychological abuse can be very damaging and could wipe out any hormetic benefits. By contrast, voluntarily taking on hard tasks and succeeding breeds a subtle sense of accomplishment that itself is beneficial.

      If one is facing unavoidable abuse, it may still be possible to turn this around with the right attitude. I think of the Stoic slave Epictetus who realized that his bondage was only physical and his soul was free if he did not lose his integrity. James Stockdale famously endured years of torture as prisoner of war in Vietnam in the 1960s, crediting Epictetus’ writings for his ability to endure and even thrive. (See my post on Stoicism for more discussion of this). One should also consider that the level of stress that is hormetically beneficial for one individual may be either excessive or ineffective for another. I believe that my ability to endure stress has increased significantly since I started practicing Hormetism (the controlled application of progressive, intermittent stress), so I assume that most people can also increase their stress tolerance.

      Daan, based upon your name, I assume you live in the Netherlands or grew up there. My work has taken me to Amsterdam, Leiden and Delft over the years and I really like that country and the Dutch.

      • Daan van den Bergh

        Hi Todd!

        Thanks for your reply. Again, the topic of your blog is simply brilliant. It brings me much of inspiration. Currently I’m analyzing your topic to the fullest, which is why I’m asking you these questions, on your blog as well as inoveryourhead.net.

        And yes, I live in The Netherlands! I grew up in Amsterdam and moved to a more quite place to focus on my writing/blogging; Groningen.

        Interesting that you mention Epictetus. I’m personally a big fan of greek history and mythology. I’ll be sure to pick that up too in my study! 🙂

        If your work ever takes you to The Netherlands again, let me know thru Twitter, Facebook, whichever you’re on, I’m on all of it. Maybe we can exchange ideas over coffee!

        Again, thanks for the reply and inspiration!

      • Daan van den Bergh

        Todd, I have a short addition to your answer — partially an answer to my own question.

        I have experienced quite some trauma in my life; coming from an abusive home. Simply finding out about the Stoic philosophy has helped me a lot. If you’re a ‘thinker’ like me, simply reading up and empathizing with Epictetus is a big help to change your perspective on past experiences.

        Since I discovered your blog, I’ve found a lot of support and solutions in the Stoic philosophy. I’m sure I’ll share more with you along my journey of self-repair.

        thanks again!

        • Todd


          Thanks for sharing your experience. I share your high regard for Epictetus and am amazed at how his answer to the question of suffering is as pertinent today as it was more than two millenia ago. While there is no substitute for reading the original writings of Stoics like Epictetus, Marcus Aurelius and Seneca, I think that William Irvine’s “A Guide to the Good Life” is one of the most illuminating modern interpretations of Stoicism that I’ve read. If you haven’t already read it, I’d heartily recommend it.

          By the way, I’ve checked out your blog and very much like it.

          Happy New Year!


  3. This is an excellent intro to fasting for anyone interested. I’ve found some spectacular benefits from fasted training, and I think many of the common complaints are not because fasting is bad, but because it’s exposing other negative lifestyle habits such as carbohydrate dependance and insulin sensitivity.

    I would caution people who are metabolically unhealthy to get their diet and lifestyle in order first, and then try IF. Although it is an amazing technique for fat loss, muscle gain, and general health, it won’t make up for poor diet and lack of quality sleep.

    Thanks so much Todd,


  4. Clint - Crude Fitness

    I’ve been training fasted since January 1st, 2011 and have seen better gains, and more energy in the gym than all of my previous years of training put together.
    I highly recommend it 🙂

    • I am the opposite having been training all my life with a variation of the 5 – 6 meals a day method. A post on a different blog has started me looking into the theory around fasting. Eat – Stop – Eat is getting very good reviews but I really like to come up with my own thing. Thanks for the post, it will help with ideas when I am putting my plan togeather.

  5. Honestly training while fasting is actually really great, for whatever reason people have reported higher energy levels than normal, not to mention the forced fat burning result.

    Just avoid the treadmill, you don’t want a dizzy spell when running full speed.

  6. Austin

    Todd: another (hopefully) quick question for you. I am working to make strength/size gains by going to the gym and having whey protein (and sometimes a lot of extra food, in general). Any ideas on how to incorporate IF into my regimen while still maximizing strength/size gains in the gym (which requires more calories)? Thanks, Austin


4 Trackbacks/Pingbacks

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