Dear Mark: Burning Off Holiday Sugar, Long Bike Commute, and Low Calorie Diets for Teens

Christmas cookiesFor today’s edition of Dear Mark, we’re answering three questions. First up, how can you mitigate and overcome an acute holiday sugar binge? What are the best exercises for getting rid of all that sugar, fast? Next, is a long (like, really long) bike commute congruent with a healthy Primal lifestyle, assuming you also want enough energy and time to lift weights, run sprints, and play with your kids? And finally, are there any downsides to calorie restriction in teens? Probably, so read on to find out.

Let’s go:

Greetings Mark!

I would like to know, given this time of year with abundant tasty treats laying around, what you feel would be the best way for a person to quickly run the sugar through the system and out of their body after say…making out with a tray of Christmas cookies?



What you want to do is clear out glycogen from your muscles. Glycogen is the storage form of carbohydrates, and by depleting it, we make room for the carbs we eat. Ideally, you’ll do this before you consume an unhealthy amount of sugar. Draining your glycogen stores sensitizes the muscles and clears out space for the sugar to go. Then, you eat a face full of cookies and it’s less of a problem to find space for it.

But exercise works whether you do it before or after (or, I suppose, during).

Best things for sheer glycogen depletion are sprint intervals. Get on the bike, the track, the hill, or the rower and crank out some sprints with minimal rest in between. I like running hills: sprint up, walk down, repeat. Tough, but fair.

CrossFit WODs rival sprint intervals for glycogen depletion. They’re full body, high intensity, and offer minimal rest. You’re basically always moving and burning glycogen when you do a CrossFit WOD.

Tabata bodyweight squats. For 20 seconds, do as many air squats as you can. Maintain form. Rest for 10 seconds. Repeat seven more times.

Tabata kettlebell swings. Same as the squats, only with swings. Use a weight that’s comfortable. Go a little lighter if you have to. You want to be able to maintain good form for the entire four minutes, not hurt yourself.

Burpees. Six sets of 10, or three of 20. More if that’s too easy. Minimal rest. These are nice because they engage the full body: arms, shoulders, chest, legs, glutes. The more muscles you use, the more glycogen you deplete.

Any of the ten-minute workouts from this post would do the trick. They’re quick, to the point, and can be performed at home with minimal to no equipment. Also be sure to check out the Workout of the Week archives for some ideas.

Lower intensity stuff works, too. A bike ride, a quick jog, anything to get your body moving.

You could even just go for a walk. A 20 minute jaunt is enough to lower postprandial blood sugar. Longer walks are even better and can also reduce the postprandial insulin spike.

But if I were trying to break out all the stops, here’s what I’d do:

Go on a hike, making sure to choose a trail with a lot of elevation and tons of large rocks, trees, and other things to climb, scamper across, and play on. Then, hike it. And play while you do it. Climb the trees. Pick up a big rock and carry it for 50 yards before dumping it. Sprint up the hills. Crawl for twenty yards, then crawl backwards. Leap from rock to rock. Do pullups on tree branches. Take detours; see that little deer track leading off to the right? Go check it out and see where it leads. Move and contort your body as much as possible. Breathe heavily, work up a sweat, and feel a burn. It’ll be fun, you’ll have a blast (especially if you convince everyone else to come along), you’ll get fresh air, and you’ll get an intense training effect in the process.


I’ve been reading and comparing your High Cost of Commuting article against the many Chronic Cardio articles you’ve written and can’t exactly find an answer to my question, which is:

I currently drive to work, but am wanting to start biking to work again like I did over five years ago (before going Primal). However, due to the distance of the ride (16 miles one-way, 32 miles a day) and my desire to make the trip as quickly as possible, I am concerned that this will fall into the “chronic cardio” category (especially since I still want to sprint once a week, lift twice a week, and play several times a week–think volleyball, pick-up basketball, rough-housing with my boys, etc.). To me, getting to work using my body as fuel seems undeniably primal, not to mention that the old car I drive to work is devoted to that purpose alone, so I would eliminate the need for it.

I do also have a couple options combining biking with public transit, which would cut my overall biking mileage in half or by a factor of four while also reducing my total commute time a bit each day compared to biking the entire distance.

So, chronic cardio or Grok-approved?

Many thanks as always,


Yeah, that’s a tough commute. Going as fast as you can for 32 miles a day wouldn’t leave much space in the week for other physical pursuits. Say you’re doing 15 miles an hour, which is vigorous (but not close to all-out) pedaling. Depending on elevation changes, tire pressure, your body weight, and other variables, that burns about 800 calories an hour (PDF), so you’d be looking at an energy expenditure of around 1,600 calories a day just from the commute. More if you really push it. It’s one thing if you’re a professional athlete getting paid to train. It’s another if you’re balancing all that training with a job, a family, and other forms of exercise. You’d need to eat a lot more food (which could be a plus or a minus, depending on how you see it), get perfect sleep, manage stress like a champ, supplement wisely, and you’d be exceeding the “don’t burn more than 4,000 calories a week” limit by a lot. Chronic cardio territory is likely.

If you decide to do it (and it sounds like you’re pretty set on it; I know the feeling!), this is the perfect opportunity to try out heart rate variability monitoring. This will give you objective feedback for tracking your recovery and planning your training so you can avoid, or at least hold off, destroying yourself.

I like the idea of combining biking with public transportation. Maybe go halfway on public transport, making your commute 8 miles each way. That’s not bad at all and can work with the rest of your desired training schedule.

Another option is to stick your bike in the car and drive to work Monday, bike back home that night (leaving the car at work), bike to work on Tuesday, drive home Tuesday night, and repeat as desired for the rest of the week. This will let you bike as often or as little as you want, need, or feel up to doing. And it also gives your legs a rest. I couldn’t imagine doing 32 miles a day and trying to squeeze in sprints or squats. The downside of doing this is you can’t get rid of your car.

You could work sprints and lower body work into your commute. Once or twice a week, throw in some all-out sprints as you ride. Sprint between traffic lights. Sprint up the hills. Toss in a 30 second sprint every two minutes. Round it out with some deadlifts or kettlebell swings for hamstring/posterior chain work (cycling is really quad-centric and you need balance) and you’d be in good shape. Heck, if there’s a playground with horizontal overhead bars along your route, stop in and get pullups out of way.

If/when you undertake this commute, avoid rigidity. Allow plans to change. Don’t feel obligated to make the full commute every single day as fast as you can and rush home to hit the weights or play ball or whatever if you’re not feeling it. Be flexible. This is where HRV monitoring can really help because it tells you — empirically — if you’re recovered enough to do the commute or squeeze in the workout. It tells you when to be flexible and when to stay the course.

Good luck and let me know what you decide to do!

Hi Mark!

I was wondering what the effects of a low carb and/or low calorie diet on testosterone as well as brain function, especially for a developing adolescent male.


Well, it depends. If the teen happens to be obese (hopefully not), caloric restriction should actually increase testosterone by improving testicular function and reducing body fat, which has the tendency to convert a portion of circulating testosterone to estrogen.

But besides the treatment of obesity, I wouldn’t advise low calorie diets in growing adolescents. Teens aren’t just smaller, more impulsive humans. They’re sex hormone factories operating at full capacity, building new biological machinery like it’s wartime and the government’s infusing massive amounts of cash into their coffers. For those hormones to work and those bodies to grow and develop, they need food and nutrients. Shortchanging the coffers with unnecessary calorie restriction is not advised.

There’s evidence suggesting that calorie restriction just isn’t a good option for teens. For instance, one paper found that skipping breakfast led to lower cognitive function, with teens who ate breakfast performing better on tests and reporting higher energy levels. And across most of the literature available, breakfast consumption is fairly consistently associated with better academic performance, although there are other variables that could confound the results. Then there’s anorexia, which is particularly devastating to the cognitive function and brain health of teenagers. In teen girls, the cognitive impairments caused by anorexia are associated with hormonal disturbances; I wouldn’t be surprised if similar hormonal effects are found in severely calorie-restricted teen males, too. Anorexia is an extreme example of caloric restriction, but it showcases the potential dangers of insufficient food intake during development.

If the teen in question is just trying to lose weight, increased activity levels actually work fairly well in the adolescent population. I usually recommend a focus on diet before exercise for people trying to lose weight and alter body composition, but it works a little differently in teens. In my experience, overweight or obese teens respond better to increased activity than overweight or obese adults. Less likely to be “metabolically broken,” teens tend to match their calorie intake to their activity levels pretty rapidly — provided those calories are coming from nutritious whole foods like animals and plants rather than processed junk, sweets, and refined grains. You can simply have them train (or ideally play) a little or a lot more than usual while eating sensibly (Primally) and the weight will usually come right off without having to drastically reduce food intake.

It’s a similar story for carbs. Very low carb diets aren’t necessary in healthy teens, in whom cravings will usually follow requirements. If they’re training a lot, maybe playing sports after school, they’ll probably want — and need — a few more carbs. If they’re not as active, or if they’re active but not actively training, they’ll probably want — and need — fewer carbs. I don’t like to limit macronutrients in healthy children and teens, because chances are they don’t really need to do it. Obese teens are a different story, of course. They can benefit from lower calories and carbs, but your garden variety teenager who’s a little worried about the pudge on his stomach should probably just play a sport, eat more meat and veggies and less pizza, go for hikes on the weekends with friends and family, and think about lifting some heavy things.

If the teen doesn’t need to lose weight, there’s no need to consciously reduce calories. It’s way too early to start worrying about life extension through caloric restriction or anything like that. A teen’s quality of life — and hormonal and cognitive health — is better served with sufficient calories.

That’s it for today, everyone. Thanks for reading!

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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23 thoughts on “Dear Mark: Burning Off Holiday Sugar, Long Bike Commute, and Low Calorie Diets for Teens”

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  1. I personally applaud Weslee for wanting to bike to work. I think 32 miles a day is probably too much to do all the time….perhaps bike to work 2-3 times per week? This allows you to burn a good amount of calories, allows more flexibility, still saves a ton of gas, and saves some of your energy for your other workouts.

    Adapt and make it work for you! Wishing you best of luck!

    1. I’m curious, what daily cycling mileage would fit the primal criteria if one were to want to maintain a schedule similar to this man’s?

      1. There’s many ways to look at that. I think Mark’s article (linked above in this post) talking about the 4000 calories a week is a good starting point. Also ensuring his HR stays in the low-intensity zone is another good thing to monitor.

        At the end of the day, I’d say the best thing would be to gauge how you feel and adjust accordingly. Do you always feel drained? Do you have the energy to do your other workouts? Does biking everyday just make you feel cruddy?

    2. Late to the party, but I like electric bikes – they allow you to do the moderate-aerobic level of a brisk hike up a hill, combined with a much faster travel pace.

      I ride about 100 miles a week – so about a third less than Weslee is proposing – and I am pretty sure it never gets to chronic cardio due to the assistance of the electric motor.

      Not primal, of course, but environmentally sustainable, and it’s been doing wonders for my health! 🙂

      1. I agree and when I was working I rode mine every day. My miles added up to over 5,000/year just on the E-assist.

  2. Exercising off excess sugar might work but it’s probably unnecessary since it should be a once in a great while thing. One needs to remember you can’t out exercise a crappy diet.

    1. But exercise works whether you do it before or after (or, I suppose, during).

      How about INSTEAD OF?

      1. Yes, if you quit sugar completely, including honey, maple syrup and coconut sugar, you won’t crave these things anyway. The fructose content is particularly damaging, but also very addictive.

  3. I binged on sweets and other heavy carbs on Christmas. I felt pretty bad the day after. Got back on the horse, went to the wilderness for the weekend and all is well again. I’m glad the impact was low but I don’t really want to repeat it.

    1. I did pretty much the same thing with the binge (though if I actually measured my intake, it was probably less than 300 grams of carbs for the two days) and followed Tim Ferriss’ damage control protocol.
      Did a monster workout in the morning – burpees, squats, and a few heavy sandbag deadlift sets – then binged away while drinking a ton of water, coffee, and green tea. For good measure, I fasted for 20 hours after the last meal too.
      I still felt gross and gained eight pounds of mostly water weight – it’s gone now – but came out fine.
      I was able to enjoy the treats and side dishes I grew up with for two days, then back to “normal”.

  4. That is a serious bike commute, wow! I like the idea of having another option for him because some days it might work but others it just might be too much. And I’m glad you didn’t advise low carb or calorie for teens. Definitely more harm there than good for an average teen!

  5. Back in the day I used to love riding to work; early morning, fresh air, high energy. But after a long, hard day at work the ride home was typically a lot less appealing.

  6. Weslee,

    I ride 30 miles a day and maintain a primal and low carb diet. I also do daily bodyweight calisthenics. I ride every day I am physically at work (sometimes I work from home but not often), year round, have been doing it consistently for years, and am a 49 year old male. I have had the “is this chronic cardio?” concern more than once. I love biking to work and it’s an important part of who I am. Here’s how I have worked it out: 1) It gives far more than it takes. I’m sometimes tired, but overall the net is positive. Very positive. I despise driving or taking subway to work. 2) I gave up a long time ago trying to go fast. I go slow with upright handlebars and look around and smell the roses and have fun and don’t worry about getting passed. This way it takes me an hour to get to work, a little longer to get home, which is only 10-15 minutes more than driving (I’m in Northern VA/Washington DC). I breathe hard on the hills but the rest of the time not at all. So to me it’s a bit like sprint sessions. 3) I save around $350/month in gas, parking, car maintenance. Hard to ignore that.

  7. Weather permitting, I ride 17 miles to work — usually only one way, taking public transit back home. It’s really not that far. On a good road bike, with a friend, it takes me about an hour. Driving door to door takes about 30 minutes, and public transit (calculated door to door since I have to get to the station) about 40-45 minutes. So it’s hardly that huge a time commitment. But if Weslee doesn’t have a public transit alternative, that return ride at the end of the day can be pretty tough! That said, there are folks on my route who have been going both ways for years — decades even.

    BTW, when I do ride with a buddy, we trade pulls and almost always do a town-line sprint, so my commute ends up including play, intervals, and sprints. It’s a lot of fun!

  8. If you can combine biking and public transportation you can also opt to do Mark’s option to alternate driving and biking with the bus rather than your car.

    As for how to handle a binge, a fasted morning hike usually helps. Helps whether or not the binge was too much sugar or just too much whatever. Seems to restore feeling like you are “back to normal”.

  9. I like Mark’s advice here. Personally, I have a similar situation, and although in my mind I had Idealized this bike only commuting (for me it is 22 miles each way), it generally doesn’t work for me schedule-wise. Instead, I have a few variations on bike + public transpo.

    Minimum daily: Ride 3 miles to commuter bus. Bus to work and back. Ride 3 miles home.

    Medium ride: Ride to commuter bus. Take bike on bus, and get off half way to work. Ride the remaining way in. Reverse for commute home.

    Maximum: Same as above but ride all the way home.

    I really enjoy bicycling. Most of the time, I just do the first option, and mix in the other choices as time and desire permit. I sold my car six months ago, and haven’t looked back. Hope that helps.

    BTW, one other option you may consider. E-bike. They go fast without excessive exertion on the rider. I think as the bike infrastructure catches up, these will become very popular for longer distance bike commuting.

  10. I actually tried some quality desserts this Christmas (eg good ice cream, cheese cake etc) and a bit of beer etc.

    I went into it glycogen depleted and put on a few pounds of water after a few days (muscles felt fuller etc) – water weight went away as quick as it went on (though starting condition is probably a factor in this for most people).

    Actually felt good through-out the course – Perhaps there’s something to intentional carb refeeds.

  11. I’d love to take a hike as suggested, but tomorrow’s high temperature is 3 degrees with snow so it’s squats and treadmill for me. Happy winter!

  12. I have it perfect or near perfect: bike ride to work is 3.6 miles each way. Once a week I leave the bike home and do it walking.

  13. I biked to school 14 miles each way for about 6 months – I ate like a horse and still lost weight and gained muscle (quads). At the time i felt super-fit but some days in the wind and rain (winter in England) were pretty grueling. If I were to do something similar again I’d get a good folding roadbike that I could take in a car or on the bus, because whilst some days I felt great, some days were a slog – better to have alternatives so that you bike when you want to and not because you have to. I agree with Christopher that a bike with an electric assist would probably be a good option tho’ you’d need to research the market and they aren’t particularly cheap.

  14. As somebody suggested earlier, I would highly recommend an electric bike for commuting. My commute is 7 miles with some killer hills, but using the electric bike means I can do it in half an hour and don’t need a shower when I get to work! On the way home I turn the power to minimum and put some more effort in, even switch it off entirely and do some sprints if I need to. The bike will pay for itself within a few years as well with the savings on fuel – I LOVE my electric bike!

  15. There are far too many factors that affect cycling speed to translate a speed to caloric expenditure, but 800 calories per hour on a mostly flat route is going to require well over 20mph. The most accurate way to count calories is with the help of a power meter. An untrained athlete usually can sustain about 1w/lb at threshold. They can’t hold threshold for anywhere close to an hour, but assuming they could, it would be a terrificly difficult effort, not something you could do every day. A 200lb athlete would exert about 172 calories in an hour. Muscular efficiency is only about 22% so this is a burn of around 800 calories.

    In general, even when training, and as an elite amateur at 180 lbs, I have trouble maintaining 750 calories per hour (mostly because you wind up coasting for more time than you think).