Who Should (and Shouldn’t) Try Fasting?
Last week, my post on the “Myriad Benefits of Intermittent Fasting” opened up a can of worms. In it I discussed how fasting can have a positive impact on human longevity, blood lipids, diet compliance and neurological health to name just a few of the potential health benefits. Naturally, many readers wondered if they’ve been missing the boat on IFing, and whether they should start skipping breakfast, lunch and dinner ASAP. In fact, who needs food anymore when you have IF! Not so fast.
Fasting can be an effective lifestyle hack, but is it right for everyone?
Not exactly. Not always. In other words, no. Let’s take a closer look.
Intermittent fasting is a tool that can be used – or misused – in the pursuit of health. As Keith Norris might put it, it’s something to add to the quiver. A tool to be drawn upon when the time is right. You know what? Let’s extend this archery metaphor, possibly to the breaking point (a skill I’m well-known for). Let’s go ahead and butcher Keith’s neat and tidy and effective metaphor with a look at a fictional monster-hunting archer with a quiver full of specially designed arrows. This monster-hunting archer, if he’s any good at what he does (and I’m going to assume that he is well-versed in classical monster lore, including weak points and monster food allergies and heavy metal sensitivities), is going to pick and choose which arrows – which tools – to draw from the quiver based on the context of the situation. Now, does this archer reach for any old arrow when faced with, say, a vampire? No, he goes for the wood-tipped garlic-laced arrow. He’s not going to waste the silver-tipped arrow on the common henchman (being a soft metal, it might not even pierce the armor, let alone kill the guy). He’ll save it for the werewolf. The metaphor is probably mangled beyond recognition now, but my point (shakily) stands: IF is a tool to be used in the right context. Zombies, for example, are particularly vulnerable to fasting because their satiety hormones are all out of whack.
So what’s the right context for fasting?
You might say that the perfect context for fasting was our ancestral past. Industrial food didn’t exist so metabolic dysfunction wasn’t an issue; “exercise” was either intense and brief and infrequent, or low level and drawn out; stress was acute, rather than chronic; and eating one or two large meals was the natural result of having to hunt and gather. We can’t return to those times, so we do what we can with what we’ve got today. Avoid industrial foods, exercise like you’re a hunter-gatherer, and limit chronic stress by sleeping, sunning, doing things that make you happy, and avoiding things that crush your soul. If you’re doing all these things and feeling like you need a final push to lean out or jumpstart the weight loss after a plateau or explore the myriad benefits listed last week, you’re probably in the right place to be experimenting with intermittent fasting. So – Primal folks who are losing weight or looking to lose a bit more, and getting the right lifestyle changes enacted (sleep, exercise, sex, leisure, rest, relaxation, mental stimulation) should definitely try fasting. They will likely flourish.
What are the wrong contexts for fasting?
An insufficiently Primal Blueprint-based diet. You have to have all your dietary ducks in a row. I recommend that anyone new to IF that wants to incorporate IF should be fully Primal for at least three weeks before trying it. That means getting rid of all excess sugar, grains, legumes, and vegetable oils, all of which conflict with satiety, metabolic function, and insulin signaling. If you are overweight, carbs should also be reduced. If lean, reducing carbs isn’t quite as important. Either way, you should be proficient in drawing upon fat as an energy source (since that’s what you’ll want to be running on during a fast), and those who are overweight or obese are efficient at storing, but not burning, fat. IF can be a good tool for speeding up the fat loss process, but it’s best used to supplement an already-strong eating plan. Once the food is dialed in, fasting will be immensely more beneficial and far less difficult.
You should also be in a good place – mentally, physically, and emotionally. Take stock of the negative and positive aspects of your life. Do the former weigh more heavily on you than the latter? Intermittent fasting may not be right, then. Get those things handled, or put them in proper perspective, and perhaps it will one day. Remember: IF is a type of stressor, and adding any new stressor (however potentially beneficial) to a heap of existing stressors will likely compound the problem. Are you the glass half-full type, the bright eyed optimist fully appreciative of just how green your own grass is? If so, you may be able to handle another stressor in the form of fasting.
You should have cortisol under control. Fasting boosts cortisol, which is not a problem in healthy folks, but in those with cortisol disregulation (think belly fat, think the skinny fat look, lack of sleep, overtraining, chronic cardio, the incessant need for coffee to keep eyes open, persistent low-grade stress) it can be disastrous. If you know you have a cortisol issue (that is, you’re actually monitoring it clinically) or even if you just suspect you do (maybe you notice the creep of belly fat accumulation, more so than in other areas), fasting may not be right for you. Get the problem handled (get more sleep, stop overtraining, stop following politics) and you’ll probably be able to reap the benefits of IF.
There’s also the grey areas. Let’s explore a few of them.
Should pregnant women fast?
There are a few studies that shed some light on the subject, most of them focused on pregnant women fasting for Ramadan. One study found that in pregnant women fasting during Ramadan, placental growth slowed but grew more efficient; fetal development proceeded as normal, but nutrient reserves were limited and there was less room for error. Assuming fasting mom has steady access to nutrients during the pregnancy, the decreased placental reserves shouldn’t be a problem for fetal development. Another study using healthy pregnant women concluded that fasting during Ramadan had no negative effects on fetal development or maternal health. In another study, LDL/HDL ratio decreased, cortisol increased, and fetal health was unaffected during Ramadan, while another found that fasting had little effect on uterine arterial blood flow (which supplies nutrients to the fetus). All in all, though the studies indicate that fasting doesn’t likely pose any danger to the fetus or to the mother, I lean toward no. I mean, why? I’m sure a fifteen hour fast is safe enough, but I’m just not sure it’s necessary or even beneficial during pregnancy. Just eat when you (and your fetus) are hungry.
Should diabetics fast?
I hesitate to make medical recommendations. In fact, I won’t. But I will point you to an interesting account by a guy who “defeated” type 2 diabetes with intermittent fasting. He didn’t call it that – he called it skipping meals – but it amounted to IF. Lee Shurie began by lowering carbs, exercising, and losing weight, which helped but did not cure him. He noticed that his blood glucose was elevated upon waking so, instead of eating immediately and spiking it further, he waited until it dropped to normal levels before eating. Now, this took a while, sometimes until the early evening, but he found that if he ate only when his blood sugar had normalized, it stayed normal all the time. Shurie was effectively IFing without knowing it, and no longer classifies himself as diabetic. Will the same thing work for every diabetic? Maybe, maybe not, but it’s something to consider. IF does generally improve insulin sensitivity, glucose tolerance, and helps with weight loss – all desirable things for a diabetic – but remember that before he was able to skip meals, Shurie had to reduce carbs and start exercising.
Bottom Line?
Bottom line, there is no concrete, objective law regarding the suitability of intermittent fasting for a particular person.
If you’re truly hungry, eat. Failing to do so will add stress.
If you’re stressed, don’t IF. You don’t need another stressor.
If you’re training six days a week, don’t IF. Unless you’re genetically blessed, you’ll need lots of fuel to prevent overtraining.
If you’re not hungry, don’t eat. If coffee’s enough, skip breakfast.
If life is good, try fasting.
In the end, the prudent path is to simply listen to your body. Don’t let CW grazing propaganda drive you to eat when you aren’t hungry; don’t let the IF dogma make you feel guilty about grabbing a handful of macadamia nuts and jerky in between meals when you are. Try it out, skip a meal, go fourteen hours or so (you already do eight every night) without eating, get a workout in, go for a walk, go about your day and see how you feel. A quick trial is not going to kill you. Remember when Primal eating sounded extreme and even dangerous? When the thought of purposefully consuming animal fat seemed sacrilegious? Exactly.
Are you lightheaded?
Are you weak?
Did your workout suffer?
Then maybe it’s not for you. Maybe you need to fix a few things (Primal eating, sleep, chronic stress) and then try again. In a perfect world, we’d all have untouched, undamaged metabolisms with jobs that we love and plenty of leisure time to spend with friends and family, and intermittent fasting would be the default eating method, but it’s not and we don’t.
How has fasting worked for you? How has it not?
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Posted By: Mark Sisson
So whats more important? Holding to
your 18/6 IF, or fasting 12 hours
before strength training? My eat
window is noon until 6pm.
It seems impossible to do both if
you are doing your strength training
in the evening. The only reason it
works for me now is because I’m only
working 3 days a week and doing
morning workouts. If I where to go
back full time there would be no
way for me to do my current 18/6,
and enter my workout 12hrs fasted.
I suppose I could cut back to a 6hr
fasted pre-workout, but that would
still put me outside my 18/6 IF by
the time I get home from work.
Don’t you see, this turns into scheduling, and Grok didn’t live
by this yoke. I’m very adamant
about a 12 fasted workoutAND my
18/6. Any thought?
I think a good fasting period is more important than a lengthy pre-workout fast.
If I were you I’d maybe move lunch an hour later, an dinner two hours later. That way you could workout before dinner in a 6-7 hour fasted state and still preserve a 17-18 hour fast between dinner and lunch.
That’s just based off of my personal experience though, your mileage may vary.
I used to eat an extremely high whole grain, low fat diet. I have always been thin, and I felt the need to eat every 2 hours or else I would feel shaky and weak. I never thought I would be able to fast.
After slowly transitioning to a (mostly) primal diet over the last 3 months, I realized it usually takes 6 hours before I even start to feel hungry after breakfast! I am not sure if IF is for me because I am generally under a lot of stress as a law student, but I was intrigued by the idea so I decided to give IF a shot today by skipping lunch. So far, so good… I am far more alert in my classes than I ever was before switching to a primal diet, and today has been no exception (I used to fight myself to not fall asleep in every class). OK, back to studying!
Great, just what the world needs. Another lawyer.
JUST KIDDING. I’m in my 19th year of practice. In a few years, you’re going to look back at law school as the glory days.
Anyway, what you wrote about hunger and how your relationship with food has changed since the big switch really resonates with me. I followed a vegan diet beforehand and was seemingly always really hungry. Not any more.
Megan,
When I was breastfeeding, I noticed a quick drop in milk supply whenever I got too busy to eat. Eating more calories and hanging out with the baby always brought it right back.
Basically, when you’re preggers, your body acts like the baby is more important than you are;it’ll eat itself, if necessary, to keep baby healthy. Afterwards it’s a different story. Your body treats milk-making like an expensive luxury: in a crunch situation, the milk is the first to go.
All of this is a long way of saying, probably IFing will make your supply drop temporarily. On the other hand, if you’re primal already and you’ve got no problem with your supply, you could try it and see what happened. It should bounce right back anyway.
I wasn’t primal at the time, but I did an allergy elimination diet that had me off legumes, dairy, and all grains but rice. So your mileage may vary!
if I try to fast/don’t eat enough while breastfeeding, I notice a drop off in milk supply as well as an increase in crankiness! :-p lack of sleep + lack of food = rawr!
doesn’t help that my baby girl is 17lbs at 4mos of age. oh well, more bacon for me!
however i am losing about 1lb a week since going almost completely pb
I love me some IF, which is ironic, since I’m a serious cook and I also love food. For me, though, the bottom line is this: I used to be hypoglycemic…REALLY hypoglycemic. I’m a very active and athletic person, and before adopting a Primal lifestyle, my energy needs caused me to eat a lot of grains, my insulin got out of control, and I found myself feeling faint if I didn’t eat every two or three hours. So, for me, the beauty of IF is simply that I can do it. I love the empowered feeling I get each week on my fasting day when I think to myself “A year ago, this would have been functionally impossible for me to do.” Now, though, fasting is easy, and that little high of achievement is hard to beat.
Wonderful post, full of nice common sense (in the good sense of the word!), no ideology, no dogma. I really enjoy reading such wonderfully informative and encouraging posts. Thanks a lot Mark!
Excellent post. I,in fact completed some research and did my first IF on Monday. The 16/8 split as advocated in Leangains also fit my schedule the best so that is the model I followed. I skipped breakfast and avoided calories till early afternoon. It was surprisingly easy….probably(in part) due to following a primal WOE.Over the last year I found myself clinging to the “grazing” concept and eating by the clock and not necessarily for hunger. It was then that I discovered IFing and another (supposedly) dietary “truth” was chucked in the dust bin.
I was curious about frequency. My initial plan is to follow a 16/8 split twice weekly on my usual recovery days(Monday and Friday).
Keep up the great work!
Geo
I always understand things better when described with the zombie models
and, I’m another one that has coffee in the am & then something around 10 or so followed by an afternoon something. Dinner is skipped most nights – not hungry.
Whilst I am a huge advocated for IF, I can easily see where negative food associations can become quite ‘obsessive’ for the minority.
As Mark says, make sure you have everything ‘else’ in check before you attempt to throw something else into the mix.
Did anyone see Dr.Oz today? It was about the HCG diet. I am fuming over this episode. This type of diet will NEVER be the answer to the obesity epidemic. To feature it on a high profile show like this seems ridiculous to me. What a load of bull. Urgh!
Dr Oz is USUALLY ridiculous and shoveling boatloads of bull! He’s a SUPERB cardiac surgeon — if only we could confine him to the surgical suite! He’s ‘expanded’ his view of himself as a miracle worker (which, apparently he is: IN CARDIAC SURGERY!!) into seeing himself as the god of all-things-medical! Alas, it’s a common problem for docs… His personality (and his good personal genetics) — and the draw of fame — has turned him into a fool.
I usually don’t jump to the defense of any TV doctor, but I saw the episode in question, and I must point out that Dr. Oz said he would NOT recommend anyone follow the HCG diet. While he does follow and endorse CW in eating/exercising, etc., what is really frightening is the impact this show has on a large percentage of the population. It’s like people need someone else to “think” for them, because if a doctor endorses it, well it must be be the right thing to do. Critical thinking skills have fallen by the wayside. I am very glad to have wisened up and developed those critical thinking skills and no longer follow the “expert” advise of any TV doc (or, really even my own GP)…always think first, is this beneficial for me and my body?
I find my IF’s are usually on the low side, maybe 14 hours or so after dinner. I do occasionally pull a 16 hour, but mostly for the ancillary benefits beyond fat loss since the PB took care of that problem area fairly quickly
wow I happened to do a 16 hour IF today.. Felt great and I enjoyed my light lunch. Will be doing a 24 hour one soon. I like the idea of a 2pm to 2pm.
Because I work in the restaurant industry, we keep odd hours already! Its actually humorous to see the staff enjoying dinner at midnight! Therefore, if I get home at 1 or 2 AM, there is NO WAY that I have an interest in food in the morning. My husband will comment on my “noisy” tummy in the morning and tell me to “eat already!” but I know my tumm tumm is just finishing up digesting whatever I consumed the night before.
I have always enjoyed fasting, and now I just eat when I am hungry. Sometimes I go from dinner (late night) to dinner on off days (normal dinnertime)..I usually have a few days off in a row, and if I want breakfast I enjoy it, although it is usually at “lunchtime”
I dont get technical about it, in fact I dont even think about it. Why would I want to shove food down the gullet if I wasn’t actually hungry? I have been on this path for awhile I guess, Hubby still eats when its “time”! (He is a 300 lb sugar addict!);)
And to all the preggo and BFing ladies out there, I was ravenously hungry during pregnancy and nursing..I also gave up dairy while nursing, gastro baby distress..it was an immediate relief for both of us!
I had not gone Primal or paleo yet, so I am sure my body would have responded differently…I will never know! Ha ha
I ate when I was hungry,(gained 50lbs, both kids, I am a healthy weight at 5’1″)My Doc was in a panic over my weight gain!I drank lots of fluids and made enough milk to keep the freezer stocked! Lost all the baby weight in 4 months for both kids, but had zero sex drive while nursing (way out of the norm for me!)
Bottom line..Do what feels right for you! (as long as your thinking isn’t clouded by “should’s and shouldn’ts”)
I started IF (sort of) when i started eating primal- i would eat twice a day instead of 3 or 4 times- no window i used to jsut mix it up (either breaky and dinner or lunch and dinner ect). I lost 2kg a week and had loads of energy. After 2 weeks I started eating three or four meals a day again (primal) and had a weight loss stall and had less energy. (partly due to the large nut intake).
Now that im back doing IF (no breakfast usually) My weight loss has started back up and energy levels and feelings of happiness has returned. I’m going to stick with two meals a day for good and i still eat the same amount i did when eating 3-4 times a day.
For me IF seems to be essential to weight loss, energy and happiness levels. But i dont use it as a tool to eat less- i just eat less often.
I’ve never been a breakfast person, so I’m relieved to find IF!
Being overweight, I always thought not eating breakfast contributed to it. Now, it seems that all that grain I was eating was what contributed to it. Since going primal, I’ve lost 8 inches off my body. I eat breakfast when I wake up hungry, when I’m not hungry, I wait til lunch. It’s all good. 
I think I’m somewhat of a natural IFer. My life is such that sometimes I just don’t get around to eating until ‘later’. Sometimes much later. My body pretty much handles it without complaint. I find it slight;y harder when I have a plan for IFing rather than it just being something that happens. Maybe just because I am more mentally fixated on food.
Coming from someone who has had an eating disorder..I find that eating primally has helped the most of any treatment.
Eating fat and protein eases my mind. Carbs are the worst, and if I eat too many of them, that is the most triggering thing.
Sometimes I will skip breakfast simply because I don’t have time to eat in the AM before work (which is about an 18hr fast), but I will still eat enough at lunch and dinner so that I don’t lose weight (I wouldn’t want to lose any weight anyway) which is easy with enough meat and fat.
Can honestly say red meat has saved my life.
On primal I simply don’t want to starve.
Natalia
Congrats, Natalia (and thanks for sharing).
I’ve been “if”ing for about two months. I have been primal about two years (with one relapse during a three-week holiday). Typically, I eat around 1:00 for my first meal (up at 7:30) and eat dinner around 7 (bed at 10:30). Sometimes I will munch on light snacks during the day, but not often. My morning is a coffee with heavy cream. So far, I have more energy and have “converted” more fat to muscle. I’m excited to continue this and find my sweet spot balance between food and energy…
I tried (intentional) IFing for the first time last week, inspired by Mark’s blog post. Since then, I’ve done one 24-hour fast and three 16- to 18-hr fasts. I’ve been amazed at how easy it’s been! My hunger has been minimal or nonexistent the whole time. Which makes me wonder… how often had I been eating previously, when I wasn’t hungry?
Although I’ve been eating mostly primal for a long time, I still have a lot of excess abdominal weight & am prediabetic, and I know that Mark mentions above that that makes me not a good candidate for IFing… but from my experience in the past week, I’ve not been hungry, not had any sort of dizzyness or other indicators of problems, and have had a noticeable increase in energy. (I’ve been a lifelong morning slug — even after 10-12 hours of sleep, I can barely rouse myself in the morning! But while IFing, I can wake early and with lots of energy, for the first time ever…) I also notice how much better food tastes, each time I come off a fast.
From the first skipped meal, I could feel my midsection shrinking, and I’ve lost a belt notch already. IF is addictive… I find myself having to convince myself to eat now…
I have to agree with you Mark. The key to any of this is being in tune with our bodies. Only by truly listening to the messages our incredible bodies are sending us can we really know when to fast and the potential repercussions it may have.
When i was a teenager i never ate breakfast. First meal of the day was lunch. Sometimes had an afternoon snack once home from school, then out to the local park to play (usually basketball) for a couple of hours or so. Home for dinner around six-ish. Never had energy lows during the day, despite being a “growing boy”.
Only started eating breakfast in my early to mid twenties “because it’s the most important meal of the day”. Load up on those breakfast cereals/toast etc and ended up feeling hungry by 10am?.
Watched a british tv show last year, where the two people in it spent one week eating the “diets” of the ages (1500′s, 1600′s, 1700′s, 1800′s etc). Only the rich were eating three meals a day. It wasn’t until the late 1800′s where “the poor people” started to eat breakfast as they could now afford it.
It’s interesting to read this article today, given that yesterday after a lengthy discussion with my personal trainer, she advised that I stop my 2 day a week intermittent fasting until I get my low carb eating happening consistently.
When I first read about IF I thought it would be a sure thing 1kg weightloss per week. It hasn’t been so I’ll go with this advice and get the primal eating under control first.
Thanks for putting this out there, Mark. I have to admit, I was confused about why I should IF when I already feel and look great with a body fat around 8-9%. I do miss a meal occasionally when I don’t feel so hungry, which doesn’t bother me, but missing two meals in a row makes me feel weak and tired, which is no fun
IFing did help me get under 10% body fat though, which can be a bit difficult without it, so I do think it’s a useful tool for weight loss.
Just giving my pic a try
Jarrett
Just did a 24hr fast the other day. Did a Mark Ripptoe workout with Olympic lifts and I’ve never felt better. That day was probably the most energy I’ve had in a long time. The only bummer was when I actually ate it made me super tired!?!?!
Hmmm, no picture….
Amen to ‘stop following politics’!
I remember the first time I tried IF without switching over to a low carb diet.
I fasted for 20 hours starting from 9:00 P.M. to 5 P.M. the next day and my first meal was one hamburger (Yes, it had a bun). About half an hour later I felt extremely tired and within moments of lying down in my bed, I fell asleep for 2 hours. Anyone had any experiences like that before when fasting and having a meal with a substantial amount of carbs after?
One of the great benefits of being primal is that it has helped me learn to tune in to the natural rhythms of my body. When i was all carbed up, I thought of food constantly and ate way too much and too often. Now, I find that things that used to send me straight to the pantry keep me from eating. If I’m really stressed out, I don’t want to eat at all (I suppose Grok needed an empty stomach to run from tigers?) Before, I would overeat during times of stress. I also naturally fast now when I’m sick. Sometimes, I just don’t feel like eating, so I don’t. Or I don’t have time to prepare and enjoy a meal. And then there’s the “bad day hunting”. This is amazing to me since I rode the carb coaster for years and was one of those people who would get really cranky when hungry. After three months of primal, I am seeing a natural tendency to IF more. I suggest people not push it but just let it happen. For the newbie, get over the CW nonsense that you have to eat every 2 or 3 hours. Once that mental leap is made, IF will not be far behind.
Did my first IF last night, having been Primal for about 7 weeks. Did it accidentally as was feeling a bit nauseous, so just didn’t eat supper.
Pre-primal I wouldn’t have been able to sleep if I hadn’t eaten – I guess my blood sugar would have been all over the place. Plus I would have got really cold and just felt totally deprived.
Slept wonderfully last night though and no feelings of cold. Noticed that I only got hungry when I remembered I hadn’t eaten – suggesting that perhaps much of my hunger is in my mind! Although I’ve only been Primal for a short while, I’m finding that my hunger seems to be out of habit, boredom or frustration. I’m gaining such a wonderful awareness of what I’m eating and most importantly why.
The idea that perhaps I now control the food and not the other way around, is quite profound for a female who’s been failing on diets most of her adult life. I’m going to do IF again, but only when it feels right. I’m learning to be nice to my body. And it feels good!
These comments are so inspiring for a newbie like me, by the way. I’m feeling so supported. Much thanks!