Dear Mark: HIIT, Omega-3s and Cooking, and Gluten-Free Baked Goods

Sprint!It’s time, yet again, for another edition of Dear Mark. As per usual, I’m doing a roundup of reader questions. First, I cover high intensity interval training, also known as HIIT. It’s the subject of an ongoing study that’s been getting a lot of play in the media, and, while we don’t have access to the as-yet-unpublished research, we do know a little something about HIIT from numerous other studies. Next, a reader asks about the effect of cooking on the omega-3 content and stability of salmon. I provide a bit of research and attempt to assuage his despondency about what he sees as a lack of reliable seafood. Finally, I give my take on the gluten-free baked goods phenomenon. Sure, it’s gluten-free, but does it belong in a Primal eating plan? Read on to see what I think.

Let’s get to it:

Hi Mark,

I just watched a PBS special called The Truth About Exercise. Much of it was centered around a study being conducted in the UK concerning how long we really need to exercise during the week to obtain the necessary health benefits.

Currently the findings indicate that 3, 30 second bursts of exercise (bike, sprinting, rowing machine, etc.) followed by a rest period three times per week could be enough.

I’m assuming you’ve heard of this and are probably getting other emails. Just wondering what your thoughts are? Is it really enough and how do we define “enough”, i.e. is it enough to keep us fit, but perhaps not enough to get that toned/ripped look many are after? I’ve included a link to an article about the study. Thanks.

Is three minutes a week of exercise all you need to get fit?


There’s not much available on this study, as it’s still ongoing, but I can give my thoughts on high intensity interval training (HIIT) in general.

In one studytwo weeks of sprint interval training, for a total of six sessions, were enough to increase muscle oxidative potential (resting muscle glycogen content) and aerobic endurance capacity in trainees. Subjects performed four to seven 30 second “all out” cycling reps, each separated by four minutes of recovery time. VO2 max was not increased, but this strangely didn’t impact or impair their aerobic capacity, which “increased by 100%.” A mere fifteen minutes of actual sprint training was enough to double endurance capacity within two weeks’ time. Increasing your muscle glycogen content at rest also means a greater capacity for storing carbs as muscle energy, rather than having to convert them into body fat, which is nice and will help protect you from obesity.

In a 2007 study, researchers discovered that the metabolic adaptations produced by low-volume sprint training are remarkably similar to those produced by traditional endurance training. Two groups of “active but untrained” men and women – people who work out but aren’t athletes – were given six weeks of either sprint training or endurance training. Sprint training consisted of three weekly four to six rep sessions of 30 second sprints with 4.5 minute rests, while endurance training consisted of 45-60 minute continuous cycling sessions, done five times a week. The sprinters spent about one and a half hours each week (with most of that time spent resting, rather than actively sprinting) on the bikes, while the endurance subjects gave up four and a half hours each week (with most of that time spent pedaling). Despite the huge discrepancy in time commitments, there was no discernible difference in metabolic outcomes, causing the authors to conclude that sprint interval training is the more “time-efficient strategy” to obtain the benefits of endurance training.

Although long distance Chronic Cardio has always been touted as the best way to improve heart health, another HIIT study showed that sprint interval training is just as effective at improving arterial stiffness and flow-mediated dilation, two markers of endothelial function and helpful ways to predict heart health.

And how about actual performance outcomes? Another study found that low volume sprint interval training conferred rapid adaptations in skeletal muscle and exercise capacity – similar to those obtained via high volume endurance training.

Even if separate those 30 second sprint intervals with 20 second breaks, you still get an anabolic effect.

HIIT was recently shown to reduce ventricular scar tissue in a 50 year old heart attack patient. It took sixty weeks, but still – that’s pretty impressive.

And finally, a recent review of the evidence concluded that HIIT is “associated with increased patient compliance and improved cardiovascular and metabolic outcomes and is suitable for implementation in both healthy and ‘at risk’ populations.” In other words, high intensity interval training is well suited both for people who like to exercise and people who hate to exercise – and it’s extremely effective.

Yes, HIIT is a “shortcut” in that it allows you to gain many of the benefits of aerobic exercise without spending all the time we usually associate with “cardio,” but they are far from “easy.” One thing you should probably know about true intervals: they’re actually really, really hard! Like, puke-bucket-strategically-placed-near-the-stationary-cycle hard. You’re essentially cramming a couple hours’ worth of training into a few 30 second chunks. That’s one reason most HIIT studies use stationary bikes – they’re a bit safer for the average person to go all out on than running. If you’re trying to test the effects of HIIT in population of seniors, the last thing you want them to do is go out to the track and run sprints. Hamstrings will be flying all over the place like broken rubber bands. But, if you stick them on a stationary bike, even the most athletically-average person can get going at a very high clip without risking injury.

If you’re going to get the most out of HIIT, you really do have to push yourself. For an out of shape fifty year old, pushing oneself will look very different from a twenty year old athlete pushing herself. It’s all relative, and if you can’t run, you can swim, cycle, row, use the elliptical, or just about anything.

However, to answer your ultimate question: is it all we need? For me, no. I enjoy movement too much. Of course, I like to stay active by playing Ultimate and paddleboarding and snowboarding and hiking and playing with my family, with a bit of strength training and sprinting thrown in for good measure. Fun stuff, you know?

If you view exercise only as a means to an end? I’m still going with “no.” I happen to feel that lifting some heavy things and lots of slow moving are also crucial and even necessary for true fitness and health. I’m particularly skeptical about the the “active couch potato,” where you work out hard a few time a week but stay relatively sedentary the rest of the time, which this approach to HIIT as the exercise panacea seems like it might promote. But you could do a lot worse than focusing on HIIT, I suppose.

Hey Mark,

Really enjoy your articles, keep up the good work. Anyway, I was just wondering something since I couldn’t find an article on the matter.

According to your research does heating omega 3 fats above a certain temperature damage the fatty acids beyond repair? Because I didn’t feel I was getting any benefit from cooked salmon but when I eat gravlax I feel I’m getting much more benefit (general wellbeing, inflammation digestion and for candida/sibo).

However, getting safe raw seafood is pretty hard these days where I live. Shellfish has generally been preboiled before selling, raw fish has risk of parasites, caviar has been pasteurized, the gravlax is always farmed etc. It’s got to the point where I wonder if I would be better of just supplementing with cod liver oil or something.

Any thoughts on this?



Cooking salmon has been shown to increase the number of oxidative cholesterol products, but as long as you’re reasonable about it (don’t pan fry a salmon filet for 30 minutes or steam it until it’s mush or anything), the omega-3s should be well-preserved. A 2010 study on New Zealand king salmon found that raw, poached, steamed, microwaved, pan fried, baked, and even deep fried fish all showed “good preservation” of omega-3 fats. Deep frying caused the most damage, but it was relatively minor.

Refined, isolated omega-3 oils are much more susceptible to oxidation than whole foods containing them. Just 30 minutes of 150 ºF exposure was enough to degrade most of the EPA and DHA in fish oil, according to one study. However, adding the antioxidant-rich herbs rosemary and oregano to the oils prevented most of the degradation. Use a nice herby marinade next time you prepare salmon (and avoid deep frying it) and you’ll have double the protection for your omega-3s.

I would stick with food over supplements, whenever possible. Your seafood choices actually aren’t that bad. Boiled shellfish? Not the worst thing. You might assume I’m shucking raw oysters and steaming fresh mussels all the time, but I’m a big fan of canned smoked oysters and those frozen bags of (quick-steamed) mussels you get at Asian markets. Plus, boiling is one of the gentler cooking techniques, so there’s little danger of degradation. Just don’t subject the already-boiled shellfish to an inordinate amount of additional cooking and you’ll be fine. Parasites? Freeze your fish for a few days to take care of them. It’s what sushi restaurants do. Pasteurized caviar should be fine, too. It’d be great to get raw fish eggs, but it’s not the end of the world. While not ideal, farmed gravlax remains a good source of omega-3s. It’s certainly better than no fish at all.

All that said, raw is probably “better,” all else being equal, especially if you’re experiencing tangible benefits from it. You might try cooking your salmon faster or at lower temperatures, as well as using antioxidant-rich marinades to protect the fats, to see if that makes a difference in how you feel after eating it.

It seems like every grocery store now has a whole aisle full of ‘gluten-free’ foods – pastas, breads, cookies, etc. What are your thoughts in general on gluten-free baked goods and the like? Craving a grilled cheese sandwich, I recently picked up a loaf of gluten-free white sandwich bread that seemed to be made mostly of rice flour and tapioca, with other ingredients that didn’t seem too threatening. Where do you see foods like that, on a ‘frankenfood/ick’ to ‘meh/innocuous’ scale? Thanks!


They’re okay, and certainly better than the alternative. Just don’t go wild on them. Most gluten-free foods are devoid of nutrition, while the foods they’re trying to replace at least attempt to provide some nutrition (whole grains, whose nutrients may be highly bio-unavailable and accompanied by antinutrients like gluten, do contain nutrients on paper).

Here’s how I handle stuff like this: don’t “waste” your gluten-free treat excursions on empty calories. Make an awesome tomato meat sauce with bits of liver, extra virgin olive oil, and pecorino romano to get with your gluten-free pasta. Make a really good grilled cheese sandwich with aged gouda, some grass-fed butter for grilling, half an avocado, and maybe a few slices of bacon with your gluten-free bread. Get a gluten-free pizza crust and smother it in fresh pesto sauce, jumbo shrimp, and fresh mozzarella. Don’t just mindlessly eat gluten-free crackers, or snack on an entire loaf of plain gluten-free bread. Make it count, if you’re going to eat it. Make your gluten-free treat a vehicle for nutrient-dense food.

That’s all for today, folks. Thanks for reading, and let me know what you think in the comment board.

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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