Intermittent Fasting

      72 Comments on Intermittent Fasting

I’ve been reading and hearing about the supposed benefits of intermittent fasting for some time now. Several bloggers I follow have recommended intermittent fasting, including Mark Sisson, Richard Nikoley, and Dr. Mike Eades. Richard (of the Free the Animal blog) in particular seems to have good success with IF. 

I never tried it, however, for the simple reason that going 24 hours or more without eating sounded rather awful. Whenever I tried very-low calorie diets, I was usually halfway to miserable by bedtime on the first day … cranky, mentally foggy, and waaaay hungry. I remember trying to get by on Slim-Fast for breakfast and lunch, only to find my hands shaking by mid-afternoon. I would be counting the minutes until dinner, when I could eat a real meal.

Of course, I tried those low-calorie diets back when I was living primarily on carbohydrates and had conditioned myself to be a sugar-burner. Now that I’m on a low-carb diet and have conditioned my body to depend primarily on fat for fuel, I often skip breakfast anyway just because I’m not hungry yet. So when I recently listened to a podcast about intermittent fasting, it occurred to me that I could probably try a 24-hour fast now without feeling miserable.

It so happened that I slept late on Wednesday, and by the time I finished dealing with emails, DVD orders, blog comments, and a couple of phone calls with clients, it was already 2:00 p.m. My last meal had been some sliced turkey at midnight, so if I could just go without eating for another 10 hours, I’d have a 24-hour fast under my belt.

I haven’t read up on intermittent fasting nearly as much as Mike Eades or Richard Nikoley, but from what I understand, the benefits are largely hormonal. Insulin levels come down, while both glucagon and human growth hormone go up. Some body-builders claim intermittent fasting not only makes them leaner, but stronger, thanks to the human growth hormone.

So, what the heck, I decided to push on through until midnight without eating. (I did, however, start the day with my usual big cup of coffee. You don’t want to be anywhere near me if I don’t get my morning coffee.)

The biggest surprise was how easy it was. I felt a few “Feed me, Seymour!” grumbles around dinnertime, but they passed. No mental fog, no shakes, no sudden urges to beat my children. I can only assume my body was doing a good job of mobilizing fatty acids and ketones for fuel.

I considered going to bed without eating, but decided 24 hours was good enough for my first fast. I ate some turkey and a handful of almonds at midnight.  (My wife, a dedicated bargain shopper, bought turkeys on sale before Christmas and froze them. I believe we’ll be having a roasted turkey once per month until the Fourth of July.)

My first fast was so painless, I decided to try a 36-hour fast next. On Saturday night, I indulged in some red wine, cheese, and two big handfuls of mixed nuts while watching “Band of Brothers” on DVD. As is often the case when I eat a late-night meal, I wasn’t hungry at all on Sunday morning. I didn’t have plans for the day other than reading and watching the football playoffs, so it seemed like a good choice for an all-day fast.

Once again, I was surprised at how painless it was. Curious as to why I didn’t have the shakes or feel light-headed, I checked my blood glucose around 6:00 PM and was surprised see it was around 95. It’s usually in the 85-90 range when I wake up in the morning. Apparently my body was adjusting with no trouble.

From an evolutionary standpoint, it all makes sense, of course. Paleolithic hunters almost certainly had to go without eating now and then, and if missing a few meals meant their hands were too shaky to toss a spear accurately, they’d miss quite a few more. We’re almost certainly well adapted to intermittent fasting, at least if what we eat day-to-day doesn’t mess up our ability to mobilize body fat for fuel when we need it. I couldn’t get by on Slim-Fast because I was an insulin-resistant sugar-burner consuming little cans of liquid sugar for meals.  Not enough sugar to get me through the day, and I couldn’t release fatty acids quickly enough to make up the difference.

I went to bed after midnight and slept like a rock. I was hungry when I woke up this morning, but the feeling went away after my first big cup of black coffee. I finally began to feel really and truly hungry around noon, which was the 36-hour mark. Fortunately, my wife had saved a ribeye steak from the dinner she served the girls last night. I ate about half the steak and a cup of her delicious chili, which is light on the beans and heavy on the ground beef.

I don’t know if I’ll ultimately continue intermittent fasting once per week, twice per week, or get bored with it altogether and stop. But since it was nowhere near as difficult as I anticipated, I’ll give it a shot for now. I’ll keep you posted on the results.


72 thoughts on “Intermittent Fasting

  1. Discostew

    The whole idea of IF, based on what we know about paleolithic times, makes perfect sense to me. Food wasn’t always immediately available for our paleolithic ancestors (fridges didn’t work very well back then 🙂 ) and going without would have been quite common. It’s certainly something I’ll be giving a try.


    Yup, you’ve got to figure even in areas where fish and game were plentiful, not every hunt was successful.

  2. Kate

    There’s been a few days over the last few weeks where I inadvertently fast for about 18 hours. Sometimes, I just forget to eat until the evening. I’m not going out of my way to do it, though. I’ll be keeping an eye out for your results.

    Unfortunately, I haven’t been to the gym since before Christmas, so I don’t have a baseline weight measurement — we don’t have a scale at home. But I know when I’m getting leaner. My belt tells me.

  3. Jamie

    Great post Tom. Exactly my experience too in terms of not being able to even contemplate IF whilst I was a sugar burner. As soon as I was fat adapted, it became very easy to go without.

    I think we can safely assume our paleo ancestors weren’t sugar-burners. They probably had to hunt in a fasted state, and I can’t imagine chasing down prey with low blood sugar and the shakes.

  4. Liz Downunder

    The ability to fast with ease has been the biggest surprise for me (and my husband) since reducing carbs. The old, carb-addicted, me HAD to eat every couple of hours or I could barely concentrate on anything else. Now a 20-hour stretch between meals is a breeze. I do wonder about the term ‘fasting’ being over-used though – skipping breakfast/eating 2 meals a day feels natural to me now, so am I technically ‘fasting’ if I’m not ignoring hunger signals? My hubby does 36 to 48-hour fasts and for him the second day is a revelation of peacefulness (tending to mild euphoria), and mental acuity.

    Amen to your comments about coffee. When I do feel hungry and can’t get good food (if I’m not at home) it’s a great appetite suppressant… Plus, I’m cheerfully addicted to caffeine.

    I drink (coffee) to that. Fasting when I was a carb addict would’ve been torture.

  5. Dave Wilson

    I routinely try to go 16 hours a day without anything but water: finished eating dinner by 6pm and nothing until 10am the next morning. The first thing I have most mornings is some decaf chai tea with Truvia, coconut milk and heavy cream, followed by four organic cage-free eggs and cheese and topped by a tablespoon of Organic Valley Pasture Butter. This usually sees me through to dinner, although some days I will stop off at the local cajun foods place and pick up a 1/3 lb of warm, fresh pork cracklins on the way to pick up my daughter from preschool.

    I find that, once I adjust to the schedule, I have no problem with 16 hours each day without food. I have read that this form of IF helps purge the body of glycated and damaged proteins in the cytoplasm as well as boost levels of testosterone and HGH.

    That seems to be a common technique for IF. Since I’m rarely hungry in the morning, it would be a logical choice … starting around noon in my case.

  6. Dave Fish

    16 hour fasting is effective as well. I’ll sometimes have dinner around 8 pm and then not eat again until noon the next day. This might be a good option for people starting out as you can sleep through most of the fast. If you are eating low carb then hunger really won’t be a problem.

    Art De Vany advocates fasting about once a week in his new book The New Evolution Diet. He claims it promotes production of human growth hormone and triggers the body to repair DNA.

    I read that some people limit their food intake to noon – 8 PM or something similar for exactly that purpose.

  7. Johnn

    Intermittent fasting is a great way to burn fat and build muscle but it boggles my mind how you could bring up the topic without mention Martin Berkhan who is the man behind Richard’s IF success and the true subject expert. He has a great blog with many good reads at Check out his clients, amazing real world results.

    Richard has mentioned quite a few people, including Martin Berkhan, Art Devaney, and Brad Pilon. I’m hoping people follow the links and read Richard’s posts.

  8. xtrocious

    Hi Tom

    Just a word of “warning” though…

    Intermittent fasting can be quite addictive 🙂

    Also recently started intermittent fasting and instead of getting weak and jittery etc, I felt more alert and did not suffer any drop in performance (went about my work and workout as per normal)…

    Your experience sounds similar to mine. I haven’t heard of the addiction angle before. I wonder if it’s somewhat similar to aneroxia.

  9. Brian

    Hi Tom~

    I was considering IF again to help shed some of the affects of ‘falling off of the wagon’ over the holidays. I just don’t know that I’m back to full-on fat-burning mode (really off the wagon this year!)

    Anyway, reading your post made me wonder what you ARE eating these days. Do you have the obligatory “this is typically how/what I eat” posted somewhere?

    I haven’t posted on my current diet, but it’s come up in comments. Mostly meat, eggs, green vegetables, seafood, and nuts. I don’t put cream in my coffee every day anymore, and I’ve cut back on the cheese, but I’m not totally off dairy. I just eat less of it.

  10. Tammy

    Tom – This topic came up at home last weekend and before my husband had a chance to overreact I pointed out that this is something he’s been doing inadvertently for quite a while. He’ll come home from work late at night sometimes and totally skip dinner if he’s not hungry and/or sleep in and skip breakfast the next day. On the weekends he’ll wake up and go walk a round (18 holes) carrying his clubs with no problem, then come back later in the afternoon and finally be hungry.

    I don’t like to use the “fasting” word in public though, people think you’re nuts – and it is true, back in my good old sugar days I couldn’t go more than 3 hours without eating which is probably where most people are coming from so no wonder they can’t imagine it. But how would the human race would ever have survived if we couldn’t go more than 3 hours without food?

    ‘Fasting’ does have a mystic-monkish connotation.

  11. Elizabeth Wells

    Interesting post. I do think there’s a caveat for people with adrenal/thyroid issues though… if you’re not 100% fit, the opposite of the desired effect can take place- body temperature and metabolic rate can drop, also if your blood sugar is unstable, it can drop as well, meaning that over-eating is a distinct possibility once eating resumes….

    I certainly wouldn’t encourage people who are still on the blood-sugar rollercoaster to try fasting.

  12. Anthony DiSante

    This does make perfect sense, considering that in hunter-gatherer times, it’s doubtful that people were eating “three square meals per day.” It seems reasonable that eating once per day may have been common. I haven’t tried it myself, but I do find that once or twice per week, I have an 8 or 10 hour stretch between eating for various reasons (compared to my normal 6 hours), and I usually think nothing of it.

    I’m not on a particularly low-carb diet, and I’m not overweight, but since discovering Fathead, BigFatFiasco, and Gary Taubes’ stuff, I’ve been seriously scaling back on the carbs, working on improving my protein+fat-to-carbs ratio. My big problem is beverages: I primarily drink sweetened iced tea, nearly a half-gallon per day, which totals around 140g of carbs. I cut that in half as soon as I realized how insane it is, and I’ve been drinking more water instead. But it seems there are few other good options: fruit juices, while “natural”, are still bursting with carbs; the same is true of soda, of course; and I’m not willing to consume aspartame or any of the other artificial sweeteners. There’s milk, but that’s not the kind of thing I want to drink all day, and it’s not particularly low in carbs anyway. So what else is there?

    I sometimes make iced tea sweetened with Truvia, but for the most part, I’ve found that the longer I’m away from sweet foods, the less I crave them. Once I shook my diet soda habit, my desire for any kind of sweet drink pretty much went away.

  13. Gazelle

    A few other words of warning:

    1. IF can trigger people who have a history of eating disorders (not just anorexia, but those with binge/purge or starve cycles)
    2. Overdoing IF, especially in combination with coffee drinking, can destroy adrenal function, leading to all sorts of unpleasant symptoms. It seems a lot of LC paleos have had this experience, once the honeymoon period is over.

    I can see where someone with aneroxic or bulimic tendencies should avoid fasting.

  14. Nicole

    My fasting BG has also gone up since I started adding IF to my day (usually 14 hours, not 24).

    My post-prandials are as good or better than before, but my morning number is about 10 points higher.

  15. Hector

    Tom, would that be dangerous for bodybuilders, athletes and exercisers who train like them?? they require more energy than the average person and I cannot imagine myself skipping meals even though I am in a low carb diet and hard training.

    I haven’t tried a hard workout while fasting yet, but Richard Nikoley does it all the time. From an evolutionary standpoint, it would make sense that we’re able to exert ourselves while fasting — hungry hunters going after the next meal.

  16. Nick

    Great post! Which podcast on intermittent fasting did you listen to?

    It was an interview with Brad Pilon, who calls his program Eat Stop Eat. I tried to find it again and link to it in my post, but for reason it didn’t come up in Google searches. I found other podcasts with him, but not the one I originally heard.

  17. mrfreddy

    I did “fast-five” style IF for over a year-you only eat during a daily 5 hour window. At first, I lost a bunch of weight, about five of my stubborn last 10 – 15. It was tough at first, but I did get used to it, for the most part.

    I finally abandoned that plan for a couple of reasons:

    1) Eventually my weight crept back up to where it normally is on low carb.
    2) I would always get brain fog in the afternoon, and would have a hard time concentrating. Even after a year or so of doing this. I ended up breaking my fast at work with small snacks just to get thru the day.

    I did discover thru this that I don’t really need to eat breakfast, I’m usually not hungry in the mornings. So I suppose I still “fast” today, in that I don’t normally eat anything till noon or later. I don’t really think of it as fasting, it’s just how I eat.

    One thing about extending your fast till you are absolutely famished… nothing ever tastes better… even turkey tastes like mana from heaven!

    That first bite of steak was pretty awesome, now that you mention it.

  18. Aaron Curl

    I will mention Martin Berkhan again because he is worth mentioning twice. He really knows his stuff and shows the science to prove it.
    I allow myself a 6-8 hour eating window everyday while maybe once a month I do a 24 hour fast. During my window I eat 2 meals, the first one is after my workout which follows the 18 hour fast. I haven’t eaten breakfast in a year! And I didn’t wreck my metabolism like CW likes us to believe. I personally experienced super fat loss when I did this routine last summer. I dropped to 7-8% body fat with very little effort. IF’ing works amazing!

    If intermittent fasting produces a hormonal shift that leads to lower body fat, it’ll be worth it. I doubt I’ll ever be at 10% bodyfat — I never had the veiny look, even as a skinny kid — but lower would be nice.

  19. Jan

    I just posted about going several hours between meals myself – nothing like 24 or 36, but it’s not uncommon in our house to eat only two meals a day, and go 7 or 8 hours between meals without any hunger at all.

    In November, I had my tonsils out and went on an unwilling 7-day fast – nothing but ice water and a little homemade bone broth for the first 3 days, and not much more than that for the next four. Before low-carb, I’d have been a mess; pain notwithstanding (and you wouldn’t believe how painful recovering from a tonsillectomy at 47 is), I didn’t suffer from lack of food as much as I thought I would. I’ve been mulling over the idea of intermittent fasting ever since (having read the same IF articles at MDA and FTA you have).

    Did anyone promise you that after the tonsillectomy, you could eat all the ice cream you wanted? That’s how the friggin’ liars sold it to me as a kid.

  20. Bullinachinashop

    This is the sort of thing I disagree with, to be honest with you. It makes no sense to me to avoid eating when you’re hungry as when my parents forced me to finish my plate when I was full. I’ve become prone to eating on demmand. If I’m really full I’ll skip a meal and eat once I fell properly hungry again, but this sort of thing is not for me.

  21. Paul451


    I believe Dr. Eades has said there’s only two ways to lose weight: [1] dont eat, or [2] dont eat carbs.

    Just after my 50th birthday, when I was 4 months into LC, I received the medical profession’s 50th birthday present: a colonoscopy. I had to fast for nearly 30 hours and it was a piece of cake…er, um… I mean it was a piece of grass-fed beef! Even after it was done I wasnt very hungry and I went another 2 hours without eating.

    It’s great to see Taube’s book out and I’m sure it will sell to the converted, but it will be very interesting to see how well it does overall. His NYT article a few years back single-handedly revived interest in LC, so let’s hope this new book does the same.

    Happy New Year, Tom!

    This books seems to be getting positive press in some major media outlets. Let’s hope that continues.

  22. Ned Kock

    Hi Tom, thanks for sharing your experience.

    In theory your brain would need about 20 percent of your calorie intake as glucose. That would be 480 calories for a person consuming 2400 calories per day. If carbs were used to fuel this, this person would need 120 g of net carbs.

    But what really happens during LC is that ketone bodies are produced and replace a significant proportion of the 120 g of carbs, as the brain can also run on ketone bodies. The proportion that is not replaced, say 50-70 g, is provided via dietary protein, via gluconeogenesis.

    If not, muscle tissue is used to keep blood glucose levels up. This means that this person consuming 2400 calories needs about 100-140 g of protein per day, assuming a 50 percent protein-to-glucose conversion rate. Otherwise he or she will lose muscle tissue, at least in theory.

    Having said the above, I suspect the body adapts further to IF, reducing insulin and glucose levels, and ramping up fat metabolism even more. This probably occurs especially at night, when GH levels go up a lot, as with the child discussed by Williamson on the post below:

    If I understand it correctly (I haven’t delved into it that much), during a fast the body will indeed digest a bit of muscle tissue to make glucose. But when the fast is followed by a high-protein meal, especially if a workout was included during the fast, the body then up-regulates human growth hormone to rebuild the lost muscle quickly. That’s one of the supposed benefits.

  23. Darrin

    Wow, you’re doing great for having just started! I generally try to skip breakfast and lunch on the days I work out. Then I eat to satiation afterward. I’ll often just wing it as well. If I’m crazy busy, I’ll just skip a meal. And if I’m really hungry, I’ll eat to my heart’s content and skip the next meal if I’m not yet hungry.

    When I read Richard’s post about working out in a fasted state, my first thought was ‘You’ve got to be kidding me.’ But after trying a fast, it doesn’t sound so bad. I was imagining trying to lift weights while feeling weak and unfocused.

  24. Jason Sandeman

    Good on you Tom! I think that because your body is adjusted to burning Keytones is a good reason why your fasting was painless. If you were still a Carbosaur, you would die after 2 hours. (Okay, only if your name was Tom Venuto and you were were worried about all them big muscles.)

    The main thing I take away from the whole IF thing is that it HAS TO BE RANDOM. Back in them days, sometimes you would just have to go without. Shocker, I know. Imagine a day without food! I think even back 100 years ago, people had to face that reality sometimes.
    Have you heard of “Nourishing Traditions” by Sally Fallon? I have been watching a DVD where she is giving a lecture on traditional diets as discovered by Weston A Price (who I think was a really cool cat.) There were people in pristine condition despite having a diet that would make most nutritionists/dietitians keel over with heart attacks.
    I took a double take while looking at a kid eating a grub worm (part of a nutritious breakfast!) but the kid looked so healthy! Now, imagine the kid had to go without for a day or so – but they still looked pretty cheerful to me!

    After watching shows like Survivorman and Man vs. Wild, my girls have well-informed opinions on which ants taste best. I’m told the red ones are spicier.

  25. Curtis

    I’ve been doing Fast-5 ( for 2 years and it feels great! I’ve been stable at my healthy weight for ~18 months now and I see no reason to eat any other way. As I see it, IF involves 2 principles: 1) don’t eat when you’re not hungry; 2) don’t get hungry. It turns out that the second one is easier than the first, but after your body adjusts, the first is also easy.

    The one drawback to IF is that your clothes won’t fit anymore.

    PS Fast5 is free of charge (and my food bill has gone down too).

    I think of most of us would happily buy new clothes in that case.

  26. Phocion Timon

    I too tried the low-cal diets to no avail. After going “paleo” I tried a short fast and it was so easy I decided to do an experiment. In August I spent two weeks going back to our typical American diet then tried a 24-hour fast. Nope, no way. I got jumpy and short-tempered, and had a major headache.

    The first two weeks of September were spent going back to Paleo. On September 11 my wife and I hopped a plane headed to the beach for our vacation. At noon on September 10 I decided to do a 36-hour fast, figuring the stress of traveling would really put me through the ringer. Amazingly, I had no problems (except for the officious security asshole at the airport but officious assholes always raise my blood pressure). We flew to south Texas and, after a bit of a hassle, we picked up our rental car and drove for an hour to get to our rental condo.

    The total travel time was 13 hours, involving two airports. At 7:00 that evening, after travelling and a 37-hour fast, I had my first meal. I suffered no problems, no jumpiness, and really amazing was the fact that I kept my temper in check. I’m not a “people person” and mixing with even a few people requires an iron grip on my temper. This “Paleo” diet, I am convinced, allowed me to go to the beach, and back, without getting mad. My wife was truly impressed (and after 28 years of marriage it’s kind of hard to impress her).

    Another amazing fact: by sticking to my diet of very low carb intake and hard exercise of short duration, I actually lost 4 pounds of fat that week. Can you imagine? Losing that much fat on a beach vacation. I still laugh about it. I still have about 80 pounds to lose but I can now see the light at the end of the tunnel.

    The standard half-junk diet definitely seems to require constant refills. I’ve seen people get cranky because they were late getting lunch, much less skipping two or three meals in a row.

  27. Lori

    This has me wondering. I normally eat between noon and 8 p.m., plus a homemade protein and nut shake (~260 calories) for breakfast and cream or half & half in my coffee in the morning. Is this considered a fast of some sort–like a juice fast, but with fat and protein instead of a bunch of sugar? It seems like normal eating to me.

    Although I felt very hungry and tired on a 24-hour fast, even though I eat a low-carb, nutrient-rich diet, I do find I can go much longer without eating than I could on a high-carb diet.

    I’m not sure if that would qualify as a fast.

  28. Cee

    I have always been a morning person–finding my most productive times to be between rising and 3pm. I have never liked breakfast but forced myself for years to comply with the “balanced” rationale of 3 meals/day. I would often postpone lunch as long as I could because after eating I would get so sleepy I couldn’t function. Had I understood during all the years of struggling with this that my nearly comatose postprandial state was classic insulin resistance I would probably not have had the life-changing heart attack that I suffered two years ago that set me on the path of ignoring all of the mainstream medical advise in favor of discerning for myself (from reading the research literature) the best path to follow.

    I have been on a PaNu diet (ala Dr. Kurt Harris) for nearly a year. I initially lost five lbs and then another 5 over the year. When my weight loss stalled, I decided to try IF to see if that would jump start my metabolism and foster additional weight loss by changing my set point. Importantly, I gave myself permission to allow my own body to determine when I would eat. It turned out that I was most comfortable and had sustained energy eating only every 24 hours or so–for me this was not fasting it was paying attention to my own signals. Since I was comfortable with this eating schedule(but still did not lose any weight) after a month I decided to try ADF (alternate day fasting) and kept a record of food intake, weight loss, and biomarkers such as blood pressure, glucose, ketones,etc.

    The first day of ADF was a little rough (probably like it is for most people who try to do their first 24 hr IF). I started to feel hungry at about 9PM. It had been 24 hours (as usual) since my last meal. After two hours of intermittent hunger pangs and messages in my head prompting me to eat I decided to stop them by going to bed. I slept through the night and the next morning, surprisingly, I did not feel hungry at all. I felt like I did on any other morning. I had morning coffee and only water with lemon juice throughout the day. I started feeling hungry about 7:30 that evening, postponed eating a little longer, and had a normal dinner at around 9. This was mid-October. I continued alternate day fasting until Thanksgiving. I lost about a pound every two days for a total of 10 lbs. I felt great the whole time. Right before Thanksgiving I did a two day fast while planning buying and preparing my first completely Paleo Thanksgiving dinner. What was surprising to me was how natural and easy it became.

    Between Thanksgiving and Christmas I went back to my 24 hour eating schedule with a few minor excursions from it based on family and guest accommodations. I did not gain back any weight during that time but stuck to my Paleo diet except for a few cocktails. Between January 1st and now I have gained close to 4 lbs back, however. I attribute this to having started doing daily body weight conditioning since New Year’s day. It has made me hungrier and probably increased muscle tone. I am going to do another stint of ADF now until I lose 10 more lbs. I plan to do a one month on, one month off schedule until I lose the 30-40 lbs I need to achieve my ideal weight. The hard part is getting started but after that if you are adapted to burning fat instead of carbs it couldn’t be easier.

    I agree it’s important to listen to your body and not eat on a particular schedule just because other people say we need three meals per day, or six smalls per day. Gary Taubes told me in an email that the so-called experts are always telling fat people they must eat breakfast, but in fact people who are insulin-resistant are mostly likely to be burning body fat in the morning.

  29. js290

    I think what fasting demonstrates is we tend to consume way too much food. The 2000 calories/day number that gets thrown around seems high. If one were to estimate one’s basal metabolic rate with the various formulas available, 2000 is way more than enough.

    Maybe if we ate the proper portions of the right things, factory farming practices wouldn’t be as necessary. As it is now, don’t we pay farmers not to grow stuff?

    We pay some not to grow, and others to grow way more than anyone needs. It’s insane.

  30. Ricardo

    Hey Tom i just wanted to share some of the benefits associated with short periods of fasting im sure everyone would agree that its quite benificial

    In dozens of published peer reviewed scientific studies, short-term intermittent fasting has been found to have the following health benefits:
    • Decreased body fat & body weight
    • Maintenance of skeletal muscle mass
    • Decreased blood glucose levels
    • Decreased insulin levels & increased insulin sensitivity
    • Increased lipolysis & fat oxidation
    • Increased Uncoupling Protein 3 mRNA
    • Increased norepinephrine & epinephrine levels
    • Increased Glucagon levels
    • Increased growth hormone levels.

  31. Jan

    Tom, no – I was actually told to avoid all dairy for several days following the tonsillectomy; it supposedly stimulates the production of mucous, causing you to clear it more than is good for a bruised and battered throat. If I had been able to eat dairy I still would have given the ice cream a pass, but I would have been scarfing down full-fat, non-sweetened yogurt by the bucket-load.

    They DID tell me to eat Popsicles, to help keep me hydrated. We bought a box of sugar-free ones, but it took only one for me to realize that the citric acid in them was going to do my throat more harm than good, so I stuck to ice water and lukewarm bone broth.

    I’m glad I read the comments section here – it has encouraged me to go ahead with the IF, but to wait until I can completely give up coffee and increase my exercise before I do any extended fasting; my poor adrenal glands will thank me.

    If coffee plus intermittent fasting is truly a bad combination, I’ll have to give up the fasting. My attemps to give up coffee weren’t pretty. And frankly, considering all the bad habits I’ve given up, I think I’m entitled to keep one.

  32. Susan

    Hi Tom,

    For what it is worth. A few times last year I was in the position of not being able to eat for an extended period of time of about 21 hours. When the hunger pains came I had to just ignore them as there was no opportunity to eat. If I remember correctly, the pains did not last overly long, just enough to let me know I was hungry. I knew I was going to be eating soon so I was not worrying about it. What I found interesting, was that after the pains passed that I had a ton of energy like I had not had in ages. I am not a runner, but I imagined that this must be what a “runners high” must feel like. I cannot remember how long the sensation lasted, but I was able to take advantage of it on my hike. I actually felt compelled to run! I cannot run at this time because of a foot injury, but I sure wanted too!


    I was surprised at my energy level too once the hunger passed. I guess the body say, “No food coming … better open the fat cells and release some fuel.”

  33. dulcimerpete

    Rest In Peace, Major Richard “Dick” Winters of Easy Company, 206 PIR, 101st.
    “Where tough men gather, he is called ‘Sir.’”

    Dick Winters refused to call himself a hero, but he was. I read his book a few years ago after watching Band of Brothers. I’m watching the series again to enjoy the special features that are included on the blu-ray release. Couldn’t help choking up a bit last night while watching one of his many interviews on the DVD series. That was one helluva good man.

  34. Sarah

    I might give this a shot too. I’m usually one to skip breakfast too and keep running until late afternoon on a big coffee with heavy cream. I notice that when I control my carbs, hunger is a lot easier to handle and goes away a lot faster. Not to mention it’ll save a bit on food bills and dishes and cooking time =P

    If I ever needed proof carbs make us hungry, the ease with which I able to complete a fast after going low-carb would be it.

  35. Richard Nikoley

    Good writeup, Tom, and glad you got past the “fear” of going hungry.

    To answer one commenter above about my own progression, I initially began fasting because ot Art’s blog. This was late 2007. My very first fast was from noon one day to about 8pm the next, 32 hours in total with a workout at the 28-hr mark.

    Over the holidays I read ESE and began going 2, 24-32 hour fasts per week, always noon to dinner the next day, with a workout around 4pm. For a good while I was dropping an average of 2 pounds per week while getting stronger in the gym.

    Once I got down to 180 I began to ease up and would sometimes do one 24-hr fast per week, sometimes not. It was only this spring/summer when I began to use Martin’s method of every day fasting. I go from around 8pm to noon the next day. Very easy. Really, it’s not like really fasting at all.

    But, once I get to my goal I’ll probably go to a less regimented deal, more random. I kinda miss doing the 24-30 to sometimes 36 hr fasts.

    The pictures you posted of your progress with IF were quite convincing.

  36. Rocky

    I’ve been using intermittent fasting to help restore the health of my glucose metabolism. As with many people here, I would never have been able to fast while on a carb-based diet. It took retraining my body to effectively metabolize fat before I could comfortably skip meals. My longest fast is three days (water fast) and at the worst, my hunger pangs were no stronger than the “It’s 1:00 pm and my lunch is one hour late…” pangs of my carb days.

    I’ve worked out extensively during a fast and experienced no light headedness or drops in blood sugar. Every day that I plan a fast I also pack food to have with me, just in case, but I’ve yet to need it.

    For those people struggling to heal an abused pancreas and increase insulin sensitivity, I think responsible fasting is a very useful tool.

    Like a previous poster said, it’s also useful to compress one’s “eating day” into a shorter period. Most carb-laden people graze like herbivores, effectively eating from 7 or 8 am until 9 or 10 pm, remaining in a glucose elevated, post-prandial state during that entire time.

    If one is an impending type 2 diabetic, there’s a lot of damage being done during post-prandial periods. Obviously, eating well minimizes just how high post-prandial glucose levels go, but for some people with higher levels of beta cell damage, even a healthy low-carb meal can make controlling post-prandial blood glucose levels very difficult. For most people, impending type 2 diabetics especially, compressing one’s food intake to 8 hours per day (e.g., 11 am to 7 pm) gives the body considerably more time to heal, every single day.

    (As an aside, the healing that occurs with fasting is further evidence that telling impending type-2 diabetics that they should eat small, frequent meals is usually misguided and only ensures that they spend the majority of their day with elevated glucose levels. Of course, this advice is only necessary because the same sources are recommending carb-based foods that are an aggressive threat to effective blood sugar control. Then again, maybe they’re right in advising diabetics to eat small frequent meals: when you’re eating poison, small doses are probably better than large ones.)

    I guess there’s a reason carnivores in nature kill, eat, then stop eating, while herbivores eat all day.

  37. Jimmy Moore

    I too thought IF was goofy, but I’ve been doing it for about a week and a half ending my meals around midday and then not eating until late the next morning. AMAZING results so far that I’ll be sharing soon.

    Looking forward to that post.

  38. Michelle B.

    Great post Tom,

    Great minds think alike because I have been interested in IF and decided to do one yesterday since I was home yesterday from work (it snowed in North Carolina) and surprisingly, I was not hungry and I felt very energized. After reading your post I will definitely continue to do it again.

    I also dropped 2 pounds in one day. Maybe this is what I needed to break my plateau and get the rest of my weight off.

    Richard Nikoley credits IF with helping him shed those last pounds. I hope it works for you too.

  39. RobR

    I’ve fasted a few times while being a carbosaurus. It wasn’t pretty.

    I went 14 days on only water when I was a vegan in 2007. (Beats how I started the diet…nothing but grapenuts and soymilk… Fathead got me with that scene)

    The first 4 days are pretty bad. Moodiness, Hunger, Weakness especially upon waking. After that I was rarely hungry, probably in a state of ketosis / lipolysis at that point, the only problem I had was occassional moodiness and dehydration upon waking.

    I did IF for about 2 weeks when I was a raw vegan eating nothing but fruit and veges.Not as easy to keep up as the pure water fasting. I was eating a lot of dates at the time which were a real kick to the pancreas…

    I accidentally have fasted lately on LC.. I have so little appetite some days, my calorie count goes way way down if I’m not exercising, and somedays I just don’t eat. If I’m not eating dairy its nearly impossible to keep my calorie count above 1500 if I’m not exercising.

    For what its worth fasting makes food taste fantastic the next time you eat. Even if you’re at your ideal weight I recommend trying it once in a while for this purpose. Its almost disappointing to eat when I’m not fasting, the food doesn’t taste nearly as good and my hunger isn’t as strong.

    You might also want to test your sense of smell. Once I go about 24-36 hours I can smell wildly well when I go outside. It seems like all of my senses really perk up when I’ve gone a while without eating.

    I definitely noticed how good food tasted after 36 hours.

  40. Howard

    The “three squares a day” comes from agricultural times, and naturally as you experienced, Tom, if you’re eating carbs you must eat more often. Over the past few thousand years societies have defined that as normal. I eat once a day and I don’t consider it fasting–I consider that normal for those of us eating mostly animal fat and protein. I do have coffee, but limit caffeine to one cup in the morning because of the adrenal thing–the rest of the day it’s decaf. I’d lay bets, though, that the reports of adrenal problems in low carbers have been overblown by nay sayers.

    When hunger came and went at mealtimes, it occurred to me the hunger was probably partly a conditioned response.

  41. Richard Nikoley

    Hey Jimmy, that’s great to hear. Hell, given what I’ve been hearing on your pcasts about grassfed beef, no sweets, etc., you’re gonna have to change the name of your enterprise to “Livin La Vida Paleoish.” 🙂

    Best wishes to you and our host Tom for 2011.

  42. Walter

    I’ve found that when I’m paleo/low carb I can easily fast for 24 hours. When consuming moderate/high carbs I can’t. I typically have one or two meals a day.

    I think intermitant implies random. I find it easiest/most natural to fast after over-eating (by accident or design) on the day before the fast. Then it just happens.

    That sounds like what would’ve happened in nature.

  43. Ricardo

    Hey Tom just wanted to know what you thought of the benefits associated with fasting

    That’s pretty much what I saw in the few articles I read. I haven’t done any extensive reading on the topic, but I’ll let my results be my guide.

  44. Sarah

    Hey Tom, random question.

    Where did you hear a link between saturated fat and testosterone levels?

    It was way back when I started working on Fat Head. Can’t remember the source and the article is no doubt sitting in a box somewhere. There are articles about diet and testosterone online, however. Here are some I found via Google:

    Notice they just HAD to warn about eating too much saturated fat in that one.

  45. J. Stanton

    Another benefit of fasting is a big boost in ghrelin levels.

    Ghrelin enhances learning and memory — in fact, it is “essential for cognitive adaptation to changing environments and the process of learning.” So if you can retrain yourself (through low-carb eating) to metabolize fat well enough not to crash into hypoglycemia, you’ll find hunger can be a major productivity boost.


  46. J. Stanton

    FYI Tom: The “saturated fat and testosterone levels” study can be found here:

    Testosterone and cortisol in relationship to dietary nutrients and resistance exercise

    “Significant correlations were observed between preexercise T and percent energy protein (r = -0.71), percent energy fat (r = 0.72), saturated fatty acids (g · 1,000 kcal-1 · day-1; r = 0.77), monounsaturated fatty acids (g · 1,000 kcal-1 · day-1; r = 0.79), the polyunsaturated fat-to-saturated fat ratio (r = -0.63), and the protein-to-carbohydrate ratio (r = -0.59). There were no significant correlations observed between any nutritional variables and preexercise C or the absolute increase in T and C after exercise.”

    Thanks for the link. I bookmarked this one. And here’s all I needed to know:

    Raben et al. (24) reported a significant decrease in resting T concentrations and an attenuation in the exercise-induced increase in T in male endurance athletes who switched from a meat-rich diet to a lacto-ovo vegetarian diet.

  47. Richard Tamesis, M.D.

    Is there a standard definition of what constitutes IF in terms of time between meals? Would eating two meals a day 12 hours apart (breakfast and dinner) constitute IF or do you need at least 18 hours between meals (dinner and the following day’s lunch).

    I’d guess it depends on who is defining the term. The few IF articles I checked define a fast as lasting at least 24 hours, but as you’ve noticed in comments, some people routinely limit their meals to an 8-hour span, creating a 16-hour fast daily.

  48. MrMox

    You can all read the book written by Weston A Price here:

    I see that it is often quoted in low carb forums. He was a racist (like many scientists at that time) but it is a very interesting book.

    I can tell you all that in Sweden the low carb diets are getting massive attention now – a new book has been published and it is the number one best seller.

    I met Dr. Andreas Eenfeldt from Sweden on last year’s low-carb cruise. He spoke about the dietary revolution in Sweden. Let’s hope we import that to the U.S. along with Volvos.

  49. Merope

    Great post! I also currently do this, à la Martin Berkhan. Although, he seems to combine building muscle and IF, and I’m going for a weight-loss phase before starting to build, more the way Lyle McDonald advocates it, since I’m not now eating enough to build much muscle, at least I think I won’t be able to. I’m definitely losing weight, and my “eating window” establishes itself automatically, all I have to do is one, not eat breakfast (the easiest, my crazy neighbour reacts to “smells” from my kitchen in the morning like I’ve started a rave party at six o’ clock anyway), and two, *remember* to eat enough in the evening…
    Oh, and, a typo on post #8 response, BTW

    I make a lot of typos in my responses to comments.

  50. Jakounezumi

    Although I only fairly recently was acquainted with the term IF I’ve pretty much done it most of my life, if for no other reason than that I’ve found cooking and eating a bit of a bother unless really hungry, eating more than once a day was, and still is a fairly uncommon event.

    The biggest difference though, for me at least, would have to be how I perceive hunger. Before LC the surest sign that I was hungry was how I started taking people’s heads off for no reason at all, and/or starting to feel nauseous and headachy. That doesn’t happen anymore, for which people in my general vicinity are eternally grateful. Hunger now is more a matter of feeling.. kind of … hollow, like I am AWARE that I probably should eat something, and I can eat fairly impressive amounts of food when I do. Still I do try to remember to eat once a day.

    I once lived with a woman who had the take-off-their-heads response to hunger. I’d sometimes end up sliding half a sandwich under the bedroom door before opening it.


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