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?

TAGS:  hormones

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending more than three decades educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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