Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...Tell Me More
Consistency is key in everything we do.
A consistent, reliable way of eating—especially with a diet like keto, where extended consistency actually builds new fat-burning mitochondria and establishes habits—tends to produce the best results.
But what if you wanted to be a little less consistent? What if you wanted to cycle between Primal and keto? Is such a thing even possible?
Yes. Just make sure you do it right—and for the right reasons.
Four to six weeks is usually a sufficient period of time. Then, once your muscles have become better adapted to the burning and utilization of actual fatty acids—not just ketones—you’re in a good place to start cycling between Primal and keto, or drift in and out of ketosis as you like.
Premature cycling without a sufficient base of fat adaptation will produce lackluster results across the board. You’ll never quite reach fat-adaptation, so the carb cravings will persist, your aerobic efficiency will suffer, and your fat burning machinery won’t be complete. And if you try to “cycle” without actually being fully ketogenic, you’ll be back at square one. Metabolic limbo is no place to be.
Don’t “cycle” because you’re five days into keto and feel terrible.
Don’t “cycle” because you miss French fries.
Don’t “cycle” because you took the stairs instead of the elevator and totally burned, like, 30 grams of glycogen from each quad.
Cycle because you’ve earned and fine-tuned your fat-burning ability, and now wish to support higher-intensity, higher-volume physical pursuits. Or because you just feel better with a more relaxed approach to macronutrients. Or because you really, really love purple sweet potatoes (I don’t blame you).
If every time you eat a carb you get sleepy in an hour and show signs of high blood pressure, even if it’s after an intense training session that should have depleted enough glycogen to make those carbs tolerable, rapid cycling is not for you.
If every time you “cycle” back to keto you feel like a truck hit you and it takes a week to get over the keto flu, rapid cycling is not for you.
Fat and carbs together is a fattening combination. Most of the worst processed junk food, the stuff responsible for the obesity epidemic—soybean oil soaked French fries, potato chips, donuts and the like—are bags of fat and carbs. They spike glucose, raise insulin, depress lipolysis, and increase fat deposition while being so nutrient-poor that you’re hungry again in half an hour. But it’s not just the junk food that makes this combo dangerous. If you’re dropping a half stick of butter into your baked potato, even if the butter’s from grass-fed cows who snacked on natto, did CowFit, and fell asleep to a Weston A. Price audiobook recording every night and the potato is an ancient heritage variety unearthed at Machu Picchu, you’re still overdoing it.
I’m not saying to “go low-fat.” I’m suggesting you reduce fat calories as you increase carb calories. What does that look like in practice? A gram of fat has roughly twice the number of calories as a gram of glucose (it’s actually 4 calories per gram of carbs and 9 calories per gram of fat, but close enough). For every two grams of carbs you add, reduce fat by one gram.
Primal has always been primarily about high-fat eating (while being agnostic enough about macronutrients to encompass moderate-carb approaches, too) and the resulting fat-adaptation. Keto isn’t the only path there.
It may take longer. You might never get to the point where you could get someone ketone-drunk by breathing into their mouth. But plain old low-carb Primal will turn you into a fat-burning beast. It’s important to realize that “ketosis” isn’t even the primary goal for most people doing it—the primary goal is building the fat-burning infrastructure that will give you food freedom for years to come.
Restricted eating windows and/or intermittent fasting are great ways to make your transition away from keto onto a higher-carb Primal approach go more smoothly. You’re not leaving ketosis entirely, since for the duration of the fasting period you’ll be consuming your own body fat and generating ketones. You get a nice guaranteed dose of ketosis every day (and night) while enjoying the benefits of relaxed macronutrient ratios—a wider variety of plant foods, in-season fruit, more carbs for athletic pursuits that warrant them.
This could very well be the dietary approach you stick with for the long haul, and that’s okay.
Anything done with sufficient volume and intensity will turn your muscles into glycogen sinks—the perfect scenario for someone trying to ease their way back to a more relaxed macronutrient intake. If you have any residual physiological insulin resistance from being keto, a hard training session will re-sensitize you.
Even if you have extensive experience being fat-adapted and your mitochondrial infrastructure is set up to utilize fats and ketones, you’ll still lose a lot of intracellular water, electrolytes, and plasma volume switching back to keto—low insulin has that effect, regardless of prior adaptation. That means eating more sodium, more magnesium, and more potassium. Salt to taste (maybe even a bit more than that), take a good magnesium supplement, and eat potassium-rich foods.
Side note: An unappreciated and keto-friendly source of potassium is zucchini. Seriously, you probably don’t realize it, but a large zucchini has very few digestible carbohydrates and about a gram of potassium. Have at ’em.
Some people suggest taking it easy during the transition. They say to let your body “ease” into the change. Hogwash. Consistent exercise is a great way to upregulate fat burning in muscle tissue. In one study, obese people—a population known for impaired fat oxidation—increased their ability to burn fat by a factor of 2.7 through moderate exercise alone. Imagine the effect it’ll have on you.
The good news is that it gets easier the longer you do this. At this point, 15-ish years into my low-carb, high-fat lifestyle and 3 years into my keto lifestyle, switching between Primal and keto is effortless. It just happens. And if I eat some carbs, I’m no worse for wear.
Of course, you don’t have to cycle between Primal and keto. Stick with one or the other. Or neither. Whatever works, works. Simply know what works best and feels the most sustainable for you in the long-term.
Berggren JR – Am J Physiol Endocrinol M (2008) Skeletal muscle lipid oxidation and obesity influence of weight loss and exercise