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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