Dear Mark: Low Energy on Primal Challenge

CalendarDear Mark,

I’m finding that I have low levels of energy in the evenings only. Could this be because my body is still adapting to primal living and adjusting to less carbohydrate intake? How long does this usually last? I’m also finding that after my sessions of intense Muay Thai training, I don’t have the energy the next day to do much of anything regarding exercise. (My Muay Thai routine includes two hours of jumping rope, calisthenics, ab work, sparring, focus mitt work and pad work in 92-93 degree heat three days a week.) Any suggestions?

Though this scenario has some pretty specific points I’ll address, the issue of fatigue seems to be a common theme in many reader questions, especially since we began the Primal Challenge.

First off, the time a person needs to adjust to a lower carb diet depends a lot on very individual factors, including how glucose dependent that person has become over a lifetime. If you’re coming down from a very high carb intake (say, 300-400 grams a day), I recommend taking it slowly. Spend a week at 200 grams and then reduce intake to 150 grams. If you can hold it at 150 for a week or so and still feel good, you can gradually decrease to 100 or fewer if you want. Track how you feel as you reduce your carbs. And during this time, try to keep everything else the same (duration of sleep, exercise routine, etc.). Trying to do too much at one time will not only set you up for fatigue, it seriously muddies the picture as you try to understand what’s behind your low energy. For the purpose of the Primal Challenge, assess the changes you’ve made this month. Make sure you’re not overdoing it in any one area, and dial back slightly if fatigue is throwing a wrench in your efforts.

True physiological adjustment to a lower carb diet can take two to three weeks as a significant shift in gene expression gets underway. (see my post on the Context of Calories and how ketosis increases with a drop in glucose intake. (Also see this great review.) And that’s if you’re wholly consistent in your low carb routine. You’ll derail the process if you go for 400 grams of carbs on a “bad day” in the interim. Not everyone will get deep into ketosis, and that’s fine. Not everyone needs to. The main point is this: you need to be in a place where you’re making the normal 200 grams a day of glycogen from fats and protein and then you are able to easily get any “emergency” glucose for the brain from dietary protein. That’s the main reason protein is high on the PB diet…you don’t really need that much, but you have it there to be used for fuel in the event glycogen runs out (and you don’t want to tear up precious muscle to achieve that). Gluconeogenesis (where the liver converts protein to glucose), by the way, is fueled by fat. Be sure you’re getting enough total calories and that you’ve added enough protein and fat into your diet to keep you well-fueled.

Secondly, I’d like to stress that duration of exercise makes a world of difference. There’s an essential reason I recommend a person stay at or below an hour for intensive workouts. The reason “less than an hour” is so critical here is that the body can only store 200-300 grams of glycogen per day on a low-carb plan. That’s enough carbo/glucose fuel to get you through an hour or less of intense workout effort, but it’s generally not enough for 90 minutes or two hours, especially in the kind of heat our reader describes and especially several days a week. The fact is, two hours of intense cardio work (whether it’s running or Muay Thai) will leave the body lethargic or craving carbs. Very possibly both. If you keep the same workout under an hour, no matter how intense, the body doesn’t begin tearing down muscle for glucose. Moreover, it recovers efficiently by burning fat and restocking that 200-300 grams of glycogen for the next day. Especially if weight loss is a goal, working with (not against) your body’s physiology will bring the best results. Occasional longer very low level (like 60% max HR) fat-burning hikes are part of a PB-style exercise program, but when you cut back your harder workouts to well under an hour (all other PB elements in place), you’ll get better results.

A good point to consider: if your workout leaves you feeling like you’re unable to do anything that night or even the next day, you’re working yourself too hard. “Rest periods” between intensive workouts are intended for productive healing and muscle building, not for getting over extreme fatigue.

Thanks for all the great questions and updates on the Primal Challenge. Keep it up everybody, and keep the questions coming!

Further Reading:

Dear Mark: Decline in Mental Energy?

What Happens to Your Body When… You Haven’t Properly Trained for Your Marathon?

Dear Mark: Weightlifting Weary

Top 10 Natural Energy Elevators

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 three decades researching and 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 Primal/paleo, keto, and Whole30-friendly kitchen staples.

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26 thoughts on “Dear Mark: Low Energy on Primal Challenge”

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  1. great question and fantastic response. I think I err too much on the side of doing too little to avoid this: feeling like you’re unable to do anything that night or even the next day.

    duly noted.

    1. I find I have – energy wise – good and bad days. I’m keeping the same routine / calorific intake, but drastically reduced carbs [tsk! don’t miss bread / pasta / grains anyhoo] but as a morning exerciser, I’ve been finding it difficult to motivate myself on getting up. The fatigue clears when I’ve set into the rest of the day, but by then I’m at a desk, and my home made medicine ball wouldn’t go down too well!

  2. Although Mark mentioned it, ‘Be sure you’re getting enough total calories’, I would like to reiterate. I had a similar problem several months ago when I committed to the PB. I was amazed at how low my calories were when I tracked on FitDay for a few days!

  3. Ditto on that, Jennifer. When I first cut out all grains and sugar, years of anti-fat messages prevented me from eating “too many” nuts and other healthy fats, and I was barely getting 1000 calories a day.

    I’ve since recovered from my fat phobia. Just this morning I had an omelette made with a WHOLE avocado! I never would have done that a year ago! I also have no fear of throwing generous helpings of cashews and almonds all over my stir-fries and salads.

    I should mention that my energy levels are fantastic when I do this, even though I’m usually at the gym for 1-1/2 hours every morning and walk and bike a lot the rest of the day.

  4. I think that decrements in energy level is extremely common when going primal, so do not fret. Slow and steady changes wins the race IMO.

  5. This post really applied to me. Since I’m new to this I’m still learning what I need. So all last week during the day I was energetic and chipper, but when I got home I’d be really sluggish. It got worse every night. Friday I came home and went straight to the couch and stayed there for a couple hours. Saturday and Sunday I worked in more carbs and I felt a lot better. It definately takes work to figure out what your body responds well to, but that’s why I like the PB, it’s easy to adjust to your own needs.

  6. How much is the enough calorie intake? Don’t you think the calorie restriction is good for longetivity? Or only the intermiting fasting can do that?
    So we can refuel the glycogen in the muscle with protein and fat? Doesn’t the old studies say we can only do this with carbs?
    Mark, I’m not that person, but what about the guy who doesn’t accept your advice and exercises with higher pulse for over an hour or more? Which is the better, living low carb and keep the exercise or go for higher carb?
    And my last question, which is kind of offtopic here, what do you think about the zone diet?
    Sorry for the many questions, but you are one of the few people whom I trust:).

  7. Although I generally agree with Marks Primal philosophy I think he may have missed the big issue here. On a pure Primal diet you can not exercise intensively or for long durations. The body will simply run out of glycogen for fuel and it will shut down and/or not be able to recover properly. In this case you have to fuel your body with carbs and protien sources pre and post workout. IMO, these should be considered “free” carbs when regarding your daily gram count due to the fact that your body almost exclusively uses that fuel for exercise and recovery.

  8. I think you can train intensively on a pure Primal diet but not for longer than an hour. If, as the poster, you are exercising intensively for 2 hours you probably need more carbs?

  9. Triguy,

    Mark knowingly states that. He’s said it many times. You can’t really be a triathlete or an endurance athlete if you are 100% primal.

    Read his earlier posts and you will see that he discourages against endurance athletics for health reasons (inflamation, higher levels of cortisol, increased requirements for CHO, etc). He is supportive of endurance athletics as a personal choice, whatever it may be, but definitely not health.

  10. Was sent the link to your blog and am loving it so far. I live in Maine and my husband and I are on a very lo carb diet right now. I don’t need to lose much but am making steady progress – 6 pounds in 8 days with only about 6 to go. Then it will be about maintaining.

    Just thought I’d say hello.


  11. Hello, Hallie! Welcome to MDA. We are very glad to have you. Take a look around our site. I am sure there will be much to enjoy as we have over 1200 blog posts. Be sure to check out the “What is the Primal Blueprint?” page. Let us know if you have any questions. Keep in touch!

  12. Mark, I’m trying to understand how glucose created by proteins and fats are used and stored. Is that ~200g of glycogen stored in the muscles to be used for exercise, or is it stored in the liver and used to fuel the brain and “day-to-day” functions?

    Also, if muscle glycogen is depleted, will ingested carbohydrates be used first to replenish muscle glycogen and then to fuel other daily functions, or are they used the other way around?

    I’d like to be able to use ketones to fuel my daily activity, but still have enough muscle glycogen stores to fuel intense exercise.

  13. I just stared the primal eating about two weeks ago. I would like to drop about 20 to 25 pounds of fat. I have been cross fitting for about 6 months now. Since I started eating primal I have been bonking during some of my early morning cross fit workouts. I am hopeful that my body will begin to adjust so I can get the most out of my workouts.

  14. I found this out the ‘hard way’ and was glad to easily find this post and am now backtracking on the original ‘totally’ cut the carbs approach. I’d just suggest that this topic be made a clear point to newbies, as I think I missed it in both the Primal Blueprint book and the 21 day Challenge book.

  15. I think I probably have somewhere in the 50 carb range during the day, but after several months on this range, and eating strictly healthy (nuts, meats, vegetables, fruit, healthy fats, and eggs) I’m starting to see that this simply isn’t enough. I struggle with low blood sugar anyway. Last summer I had a scary episode when my carbs were less than 15 per day when I almost blacked out in the car. But I’ve always understood that I need to lower my carb count in order to lose weight, and I have quite a bit of weight to lose. I’m not losing anything. Not even a pound. And I’ve been eating like this for several years. It’s become for me a matter of do I want to lose weight, or do I want to have the energy to tackle my day and play with my kids? My health is terrible. I often get sick, and I’m just so weak all the time. I don’t know what the answer is. This week I’ll play around with the amount of carbs I take in. There’s got to be an amount that will help me to feel human again.