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.


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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