Dear Mark: Cycling at Work, Refueling After Sprints, Fasting for Caloric Deficit, and PUFAs for Pain

Stationary BikeFor today’s edition of Dear Mark, I’m tackling four questions. First, I discuss the negative effects of sitting and explore whether stationary cycling as you work can mitigate the bad stuff associated with sitting for too long. Next, I explore how and why a person might want to refuel (or not) after a sprint workout. Should you fast to maximize fat burning or feast to maximize glycogen replenishment? Read on to find out. Third, I field a question from a reader who wants to know whether he should make up for lost calories after a fast, lower his calories, or go with the flow and do what feels best. You probably know what I’m going to say, but you might like reading my reasons why. Finally, I discuss the fatty acid composition of black cumin seed oil and olive leaf oil for a reader who uses both to fight muscle pain. She’s worried about the PUFA content and I try to allay her concerns.

Let’s go:

Hey, Primal Crew! I have a very sedentary job and have been working hard on incorporating standing at my workstation as much as possible. Unfortunately, I also have trouble with one foot due to plantar fasciitis. I have been looking at the Fit Desk bicycle plus desk combination for home so I can get even more active time into my life while trying to finish my next novel. Does biking time count as sitting? If so, I’ll just pad my heels more heavily and go after the treadmill desk instead. But I was really hoping to give my feet a break with the alternative. Any input you have on whether biking counteracts sitting disease would be much appreciated!

Thanks for all you have done for me already!


I’m glad to help you, Rhonda. Anytime.

As for biking and negating the negative effects of sitting, it does and it doesn’t. Allow me to explain.

The problems with sitting are manyfold, and biking addresses a few of them, but not all. What problems with sitting does passive cycling counteract?

The blunted secretion and action of lipoprotein lipase. Normally, when people are walking around, gardening, shopping, doing housework, and just basically engaging their musculature in non-exercise movement, lipoprotein lipase is active in the muscles being used. This allows you to burn fat for energy (since, well, you’re active at a low level, which relies primarily on fat for energy). When you stop moving, your muscles stop producing lipoprotein lipase (since, well, they have no real need to burn lots of fat for energy). Cycling demands lots of activity from your legs, even though you’re technically sitting, so lipoprotein lipase should remain active.

What problems with sitting does passive cycling fail to counteract?

Shortened, tightened hip flexors. One major problem with sitting for too long is the position into which it places your hips: a super flexed position, with the angle between your hips and your torso shortened. That’s why sitting for too long and then trying to go exercise can open you up to injuries – your ability to fully extend your hips is hampered and your other tissues will pick up the slack and throw something out of whack. Biking isn’t really all that different, as a perusal of biking forums will quickly show. Cyclists commonly complain about tight hip flexors. Now, since you’ll be upright, rather than hunched over roadbike-style, your hips won’t be quite so short. Make sure you hit the couch stretch at the end and beginning of every day to make up for all the sitting.

What am I not totally sure about?

Reduced insulin action. When you sit and eat, your ability to use insulin is reduced. It takes more insulin to clear glucose from the meal you just ate when sitting than when standing. I strongly suspect that cycling will mitigate this since you’re active and using your muscles, but I can’t be sure.

The lowered satiety response to meals. I don’t have a study showing this, but I do have one showing that sitting during and after a meal reduces satiety and promotes overeating when compared to standing during and after a meal. Since the primary difference is the level of activity, I’m guessing that passive cycling is roughly analogous to standing in this respect.

Slack, inactive glutes. Sitting famously inactivates your glutes, since you’re literally sitting on them without engagement (as you would, say, in the bottom of a squat). Cycling can utilize the glutes, but it often requires actively engaging them as you pedal. Most cyclists do not use their glutes to pedal, not nearly enough, which is why cyclists with massive quads and flat butts are pretty common. You might try actively pulling with your hamstrings and glutes while trying your hardest not to use your quads until you’re confident you can engage your glutes.

Overall, I’d say cycling as you type is better than sitting, but I’d still break up the monotony and get up and move around as often as you can. We’re simply not “meant” to remain in the same position for hours on end (even if we’re moving), and I suspect messing with that can have negative effects on our health.

P.S. We just added four TreadDesks to the Primal Blueprint offices. The crew is loving them. Maybe I’ll do a full-on TreadDesk review post somewhere down the line if there’s interest.


I have a question on the interaction of diet and exercise within the PB realm. I exercise in the morning before work and the days where I lift heavy things I usually follow up my exercise with a pretty solid breakfast of fats, protein, and some carbs. On my off-days, I usually just walk in the morning and will typically continue my fast until I get hungry later in the morning or lunch time. My question is around sprint days. Should I eat after a sprint day like a lift-heavy-things kind of day or like a walking day…or mix it up? I imagine Grok exerted himself with no immediate food gain afterwards [running away from a Saber tooth?], so I don’t think I’m negatively impacting my health but I’m not sure.

Grok on!


Well, it depends on what you want to accomplish. Going without food after a sprint shouldn’t negatively impact your health, and it might even improve your fat burning and boost your growth hormone production.

Generally, sprinting is going to deplete muscle glycogen, at least from the muscles that you’re using to propel yourself forward. So hamstrings, quads, glutes, calves, and even your arms (all that pumping) will burn through a good chunk of their glycogen stores. You’re going to want to eventually replenish that glycogen, and doing so in the immediate post workout window (1-2 hours) is the most efficient way to do it. In the first 30 minutes, you can actually refill glycogen without needing much insulin. After that, muscle insulin sensitivity remains elevated for awhile – in rats, 50% of their muscles’ increased glucose uptake is preserved at 18 hours post workout. So don’t think you have to go and eat everything right away or have your muscles forever locked away.

However, a glycogen depleted muscle will be a weaker muscle, particularly if it’s a fast twitch muscle fiber (the type of fiber that sprinting preferentially targets), so if you need to perform right away or need to recover for the next day’s activities, you may want to eat.

It all comes down to your goals and your needs. If you’re a performance athlete who needs to be ready to perform again tomorrow, take advantage of the post-sprint window and eat a bunch of carbs and protein for glycogen replenishment. If you’re trying to maximize fat loss, a couple hours of fasting will maximize growth hormone release and might be ideal (although eating a modest post workout meal shouldn’t affect your fat loss much, as the bulk of the glucose you consume will be shuttled into your muscles without even necessarily requiring insulin to do it at first). And you can still replenish your glycogen later that day. It just won’t be quite so efficient.

I’d mix it up. Keep eating your fat, protein, and carbs on the really intense sprint days but toss in a couple days where you fast for a couple hours postworkout. Go by how you feel, ultimately. I’m a firm believer that your body will tell you what you need, especially after training.


The question I have regards intermittent fasting. I have not started it yet but would like to. My question is, if someone normally consumes 2,100 calories a day and does intermittent fasting, say from Sunday at 6 pm until Monday at 12 pm, should you still consume 2,100 calories throughout the rest of the afternoon and night on that Monday (or the days one fasts), or are you supposed to subtract the calories you would normally eat in the morning from the total calories eaten in a day, 2,100 in this instance?

Thank you,


I think you should try to eat your normal amount. Don’t stuff yourself or force the food down, but don’t arbitrarily limit yourself either. Fasting is a potent stressor, one that we can recover from and grow stronger in the process (a la hormesis), but only if we nourish ourselves. Don’t let fasting become starvation.

Plus, there’s some evidence that even when caloric intake is steady, even when you’re eating as much as you would otherwise, simply reducing your meal frequency (i.e., fasting) can elicit favorable changes to body composition (less fat mass and body weight) and have mixed effects on cardiovascular disease risk (slightly increased blood pressure and LDL, increased HDL). In another study, rats on a high-fat diet that normally induces metabolic syndrome and obesity were protected from the usual negative metabolic effects by eating in a time-restricted fashion. Meanwhile, the rats who ate the same amount of calories on the same kind of diet without a restricted eating window suffered from obesity, hyperinsulinemia, inflammation, fatty liver, and impaired motor control.

Don’t overthink it. It’s not an exact science, or a system that requires obsessive tracking. It’s just a way to streamline your eating, to make things easier, to actually remove all the guesswork and intense focus on food so that you can relax and spend time doing other things. That’s how I see it, anyway. Some people use IF to make attaining a caloric deficit easier. With a truncated eating window, eating the same or similar amounts of food simply grows more difficult.

Black seed oil and olive leaf oil help me immensely with muscle pain. Are they dangerous PUFAs? Thanks so much.


Black seed oil comes from the black cumin seed, known as nigella sativa. Cumin is a potent antioxidant spice that provides incredible flavor and several health benefits, many of which I outlined in my previous post on the subject, but black cumin is not to be confused with cumin.

Like cumin, though, black cumin is a spice with impressive antioxidant compounds and extensive medicinal history throughout the Mediterranean. It’s a broad-spectrum antimicrobial, effective even against antibiotic resistant bacteria. According to a review on its pharmacological effects, black cumin may improve hemoglobin levels, increase respiration, lower blood pressure, and improve lipids. It’s also been shown to reduce inflammation. One recent placebo-controlled study found that black cumin seed oil was effective against rheumatoid arthritis, which makes me think of your finding that it helps with pain.

As for the oil, it’s pretty high in PUFAs. A recent analysis of black cumin seed oil found that it was 42.76% linoleic acid (PUFA), 16.59% oleic acid (MUFA), 8.51% palmitic acid (SFA), and it even had some EPA (5.98%) and DHA  (2.97%). If you’ve got serious pain issues and it’s helping, I probably wouldn’t let the PUFA content dissuade you. However, if you’re just trying to ease sore muscles after a workout, the fact that black cumin is reducing inflammation might mean it’s also reducing your adaptation to exercise.

I wasn’t able to find anything about olive leaf oil, but I would assume that it has a fairly similar fatty acid profile to olive oil – mostly monounsaturated fats with a bit of saturated and polyunsaturated fat. Again, if it’s helping, don’t worry about any PUFAs (which are bound to be low anyway).

Thanks for reading, guys. That’s it for today. Be sure to leave a comment!

TAGS:  dear mark

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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54 thoughts on “Dear Mark: Cycling at Work, Refueling After Sprints, Fasting for Caloric Deficit, and PUFAs for Pain”

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  1. Really interesting info on the fit desk bicycle. Have often wondered about that.

    Personally I think the treadmill variation would be best, you wouldn’t receive any of the slightly negative effects of the bike but you would receive all of the positive effects if not more.

    But of course the bike is far superior to the chair on all accounts, unless you’ve got a broken leg, then a chair may be useful.

  2. I’ll have to try playing around with the idea of fasting after an intense glycolytic activity (mine include Crossfit and BJJ).

    Do you think eating prior to the work out will affect the post workout benefits at all?

  3. I think it’s easier to IF when you stop thinking about IF. Just go about your day and tune into your hunger signals, you’ll probably miss quite a few meals (especially if you’re fat adapted). IF is EASY, don’t overthink the room.

    1. Agree MattyT, I find making sure I minimise carbs for the few days before (fat adapting) makes IF for at least 16 hours no worries (have dinner and skip breakfast), certainly a good place to start for anyone unsure about IF. Throw in a lunch time work out instead of lunch and you can easily stretch to 24 hour IF

  4. On days I IF, the tendency is for me to eat about the same amount of food, just in a smaller window of time.

    1. Me, too. (Though I am still finding my standing desk too much for all day. I stand a lot more now, though, and also sit on the floor.)

      1. I have a standing desk at work and average 7 hours of standing out of an 8-10 hour work day. I will sit in meetings out of respect for those I’m meeting with, but the majority of my day is standing and walking around. I also go run the stairs a few times a day. I find I am way more productive after switching to a standing desk.. just took a few weeks to get used to it. I wear minimalist footwear to work (merrills are my fave) which makes standing very comfortable! I also found that strengthening my core has helped make standing more comfortable.

        1. I agree that standing makes you more focused and productive, that’s why it is recommended to make important calls when you are standing. But as for me standing all day is very tiresome. Used to stand at work for hours and it causes pain in my knees. Since then I avoid standing jobs.

        2. I also stand pretty much all day at my work station, best thing I ever did. I do have a 2″ foam pad that I stand on that I like rather than standing on a hard surface.

      2. I third this. (Is that how you do it?) Lol. Tell us your thoughts on these desks!

        Also how well they’re wearing in. No one likes money to be wasted 🙂

        1. Somewhat recently I’ve noticed rubber pads for people working cash registers to stand on. Not sure how common that is but the principle should keep being spread. (I’d prefer something other than rubber since many varieties of it tend to allow lots of molecules to float off into the air.. know that noxious rubber smell.)
          Working in the kitchen in jail, standing in one spot at a table for hours and putting stuff in trays, my legs and back suffered, especially my knees, which were a bit rough before getting there.
          I need to move in all sorts of ways frequently to keep limber. Hiking helps.

  5. I do my sprints during water “aerobics” (not just aerobics, also sprints, resistance and flexibility). I fast until after the class, which means around 11 am. That’s about when I start getting hungry. Usually I will have bacon, eggs and fruit, and sometimes other food. Typically I eat a lot then mostly fast until dinner (maybe a few nuts in between. I resisted IF for a long time but it has helped tremendously, e.g. with fat loss.

    I am still resisting the idea of standing at my computer but I have started doing leatherwork mostly standing. While working, I do some moving around like VitaMove.

  6. What about sitting indian style at the desk? I’ve been doing this during class and it’s helped a lot with the tight hip flexors…it’s still sitting, but hey…if the bossman doesn’t okay the deskbike…maybe indian style would be an option..

  7. Hmm… and how exactly can we work the butt and hamstrings instead of the quads? Biking while standing?

    1. Either strap your feet in or use cycling shoes, then focus on the upward pedal motion – engage your posterior chain to bring the pedal up with force. We normally focus on pressing down with force on the downward motion, which uses anterior chain more, and forget about the second half of the cycle (no pun intended).

    1. Wow. I should have watched this first. It is just the opposite of so many things I have been told. I checked the trigger point areas he was talking about and that leg is lit up like a Christmas tree with points compared to the other. And stress? No, I am not over-training (well unless one counts shopping too much) but OMG my life is one big boiling pot of personal stress. Thanks so much for responding, Huarache Gal!! I needed this badly!

  8. For Rhonda, with plantar fasciitis – look into foot and ankle exercises, they really help! Also, beware of padding your heels. Better to re-learn to walk (and, eventually, to run) without heel-striking. Take it easy (and do exercises) in the meantime.

    I found barefoot shoes to be really helpful – though take it very easy at first. I wear trainer-type (e.g. Vivo Barefoot), rather than the Vibram Five Fingers (which Mark loves), and I started out with putting orthotics in them. Sounds strange, of course, since orthotics and barefoot shoes seem the opposite thing, but it allowed me to build up foot strength without igniting the plantar fasciitis. It took me a year to build up to wearing the shoes more often without than with orthotics, but I still use the orthotics if I’m going to be doing heavy walking or carrying luggage (e.g. while travelling). Good luck with your recovery.

    1. I did this to myself by overdoing the barefoot shoes. I had been wearing them for months and thought I was doing great, but a long day of shopping on concrete floors was too much for me. I have always been a very hard heel-striker and the barefoot shoes have made a huge difference in my gait so I am not going back! My knees in particular have gotten much healthier with the softer strike. Right now, I’m helping myself along with some heel orthotics inside the barefoot shoes until this foot heals up completely. I am glad to know this approach has helped you!

      1. Rhonda, for plantar fascitis and advice about minimalist shoes and how to make it all work, please look at “Every Woman’s Guide To Foot Pain Relief” by Katy Bowman. Loads of good info there. (P.S. Not just for women)

    2. I had wicked plantar fasciitis. It is an inflammation problem. Try taking ibuprofen or another anti-inflammatory regularly, religiously for a few weeks (allowing it to heal), and also targeting and eliminating any potential inflammatory food that remains in your diet. Worked for me. Also, don’t over stretch those tendons–that can make the problem worse.

    3. Good advice Violet. I, too, took a year to build up to going without my arch supports, after wearing them for 9 1/2 years. (I developed plantar fasciitis after hopping off a low step late in my pregnancy with my now 10-yr-old.)

      Rhonda, here are some things that helped me: Stretching my Achilles tendon. Picking up a marble with my toes. These next three are the helpful parts of some of the moves from my Belly Dance Fitness videos. Walking in place, with your toes and the balls of your feet being the last thing to leave the floor and the first thing to contact. Taking a step or two backwards, then forward, always with a toe strike. “Bouncing,” basically small, rapid calf raises. You don’t want to raise your heel more than about an inch off the floor. This next one, I found after developing Achilles tendonitis. Calf raises, but on a step rather than a flat surface. Stand on the edge of a step, with just your toes and the balls of your feet on the step and use a hand rail for balance. Rise up on your toes, and then lower your heels as far as they’ll go, repeat until your muscles begin to feel it, even if it’s only one or two reps. Normal walking only with a toe strike, but be careful. I did this for a minute or two and didn’t have any problems at all that day, but the next day I had my first plantar fasciitis flare up in months!

      Search the net for plantar fasciitis exercises. Something that didn’t help me, may help you.

      With all of these, start with just a couple of reps and build up as you’re able. How your foot feels later that day or the next day will tell you if it’s safe to do more or not, or even if you need to do less. You’re trying to heal an injury, not build muscle, so now is NOT the time to push yourself!

  9. Love the info! My friend and I both referee soccer. He takes an Advil after every game and I avoid painkillers. This explains why my muscles hypertrophy and his stay the same. Anyone know how long to continue the IF after the heavy workout to maximize the HGH and weight loss effect?

  10. Great post.There’s studies to show that people who fast don’t feel the need to stuff there faces after a fast. Usually the person just eats the normal amount for that time of day. Listening to the body is key in IF.

  11. Great info, especially the part about cycling. To anyone looking to counteract the effects of too much time in the saddle (especially when riding indoors), you might try increasing the tension and standing up on your pedals (as in simulating riding on a hill). You’ll feel your glutes working pronto!

    I like to put a bunch of 3+ minute songs onto an iPod playlist and ride to it for as long as I choose (30 minutes, 45 minutes, whatever). I alternate sitting and standing by song – so one song I ride in the saddle, the next song I ride out of the saddle, and so on. It breaks up the ride, works the glutes, and keeps saddle soreness at bay.


  12. Yay! My hubby, Mike, got his question posted today! 😉

    Also good to know about fasting and how much to eat after. I naturally fast from 6pm-7:15am everyday. So eating all of my calories is fairly easy.

  13. I wonder if Wendy meant Olive Leaf Extract (not Olive Leaf Oil)…


    These should help with specific PWO diet recommendations for ‘dat glycogen.

    tl;dr version: 20-30g whey plus carbs at “ratio of 2g of muscle substrate (=glucose or precursors) to 1g of liver substrate (=fructose or galactose)”.
    The perfect ratio is displayed by the humble banana. If you aren’t eating a carby meal afterwards, toss in some honey.

    That being said, take note of this:
    “While it is important to replete the glycogen stores, the advantages of doing this as fast as possible are actually not really relevant for someone who trains 3-4 times per week in order to promote health, well-being and a leaner, more muscular (but not freakish) physique. Especially with respect to the latter, the majority of the more recent studies clearly suggests that muscle protein synthesis is, in the short run, not impaired by low levels of muscle glycogen”.

    Enjoy the sprints 🙂

  15. I am an engineer. I sit all day at my desk. I must think deeply and profoundly about my interactions w computer. Standing is OK, but forget cycling or treadmills, no way! Maybe OK for less strenuous computing tasks, but not design engineering. My answer is Crossfit and taking 2-4 month’s off per year to practice martial arts in Thailand. If you have a strong core, good posture and open hips this goes along way towards wellness and long-term health. Balance is key. Fortunately I work on a project basis and am able to take significant time away from work every year. My advice is to make time for things that are important (health, wellness, and fitness) Cheers!

  16. Don’t the hip flexors get stretched out when you’re lying in bed for hours?

  17. So is it best to stand while we eat?
    I always thought it was best to sit and be focused on the meal (“being present”) and I find standing kind of disrupts thats focus. And what about floor sitting for a meal? I realize sitting in general lowers satiety rates. Thoughts?

  18. I have managed to do 24-hour IF every Sunday. Since I want to lose weight I have combined IF with caloric deficit. I eat twice a day. Usually I start my day with eggs and cabbage and eat the majority of the calories in one lunch after the work. I have managed to accomplish a daily caloric deficit of 800-1000 kcal through diet and exercise. I have been 2 weeks in this plan and I feel great so far.

  19. >> The lowered satiety response to meals. I don’t have a study showing this, but I do have one showing that sitting during and after a meal reduces satiety and promotes overeating

    I figured it out long time ago 🙂 When I sit after a meal, I immediately get hungry again.

  20. Funny, in the past year I’ve gone from never having heard of black cumin seed oil to seeing a mention about every other day. Now I’m waiting for it to show up in my spam email.

  21. I was interested in Rhonda’s question and just wanted to comment on one thing that I have noted at work (I work in a pain and soft tissue injury rehab clinic).

    A lot of our patients who have plantar fascitis and/or foot pain, Achilles tendinitis or knee pain also have chronically shortened hip flexors – usually due to a very sedentary job where they sit for most of the day. Very often we find that both Psoas and Iliacus are tight and short, often with multiple triggerpoints throughout the muscle bellies and that they have either a posterior or anterior rotation of one or both illia (Pelvic asymmetry). This usually makes one leg appear to be shorter, which puts extra pressure on one foot and that results in the irritation of the plantar fascia – along with causing triggerpoints in the leg muscles that can also refer pain down to the foot.

    From my experience, most foot or knee pain is caused by short, tight hip flexors and can be at least partially corrected by treating iliacus and psoas and hip flexor stretches.

    You are correct in saying that cycling (and especially spin classes!) also shorten the hip flexors, so standing more or the treadmill desk would be a better option as far as I am concerned, both for her hip flexors and her plantar fascitis coupled with some treatments with a knowledgeable therapist to release any triggerpoints in iliopsoas and hip flexor stretches.

    1. I should have also added, Rhonda, if you want to check if you have any rotations of the hip bones, google to find a qualified Onsen therapist in your area and they would almost certainly be able to help you as Onsen therapy (it is an osteopathic based therapy – concerned with alignment of muscles and bones and the entire body being in balance) addresses pelvic asymmetries.

      Failing that, a good manual osteopath should also be able to help.

  22. I agree that while cycling can be great for you, when you’re sitting that long it can be so painful. There are specific types of gel seats you can use to treat this. But like with everything, you need a moderation in all things.

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