Dear Mark: Running Across the U.S.

Walking Woman on a Long RoadDear Mark,

My name is Katie, and I’m planning on running across the U.S. from Boston to San Diego starting this March! I’m 23 and have been an avid runner since high school. I train on my own now and am deciding whether to run 9-12 miles a day or kick it up to an average of 20 miles a day. I’d like to understand what the effects of the two choices would be. Under the 20 mile plan, I’d run long, slow distance with some walking. The 9-12 mile plan would be the same with less walking. If I’m going slow, would covering the extra 10 miles a day be harmful to my body? What is the risk of injury and long term health/bone problems if I did 8 months of 100 mile weeks compared to 12 months of 60 mile weeks?

Thanks, Katie, for your questions. While I absolutely applaud your ambition and dedication, I’m afraid my answer is going to rain on the parade. Although you may have a very compelling reason to go the distance (I’d love to know), I have to say that there’s no way this effort (either way you describe really) can be constructed as healthy. The only considerations left then are how you can mitigate the damage of your trek. Any elite/endurance athlete faces health compromises as I’ve described in the past, and your case would definitely be subject to some of the hardest of those health concessions.

Some key questions come to mind also as I think about your situation. What’s your running background (e.g. distance training)? Are you trying to break a record? If not, is there a necessary time frame? If not, could you extend the duration and just walk? I’m particularly interested in your training plan and the inevitable toll it will take on you before you even leave Boston. Let’s say you train 100 miles a week for 8 months. In this case you’ll run some 3300 miles (more than the trek itself) just in training. The training, logic says, could be more damaging than the event itself.

I also wonder about your plans for fueling yourself. If you walked the trek, you could go 30-40 miles a day and manage it on a lower carb diet with careful planning and some dietary “training” (so your body can rely on fats and ketones). Otherwise, you’ll likely need a hefty amount of simple carbs to get you through your trek. Working at high levels of exertion day after day, month after month (the ultimate chronic cardio) inevitably depletes natural glycogen stores and leaves you dependent on carb loading. Constant fueling with simple carbs, of course, boosts inflammation. The results? Loss of bone density and muscle mass, and increased susceptibility to just about everything under the sun. You asked about the risk for health problems. Check out my friend Art De Vany’s article that offers a detailed vision of what your body goes through in endurance training and events.

Everything from serious muscle damage, spine degeneration, kidney damage, and a shifting of biological markers that indicate cardiovascular stress, brain trauma and higher risk for cancer.

All this said, I understand there may be a reason compelling enough to convince you to move ahead with your plans (e.g. raise money for a loved one who has a disease). In good conscience, I have to caution you against the trek for health reasons that go far beyond usual athletic “primal” compromises. If other motivations keep you committed to the task, however, I’d urge you to take it slowly and use the PB to inform your diet and exertion plan along the way. In fact, this would be my ultimate suggestion to someone that wants to traverse the country by foot. Consider turning this into a truly Primal event. Imagine the goal is to migrate (instead of race) across the U.S., stopping periodically for push-ups and doing sets of sprints every few days along the way. This way you could stay on a high-fat diet to fuel your efforts and turn an unhealthy endeavor into something that is perfectly Primal. (And, it goes without saying, make sure you seek out expert medical observation throughout the trek.) Good luck to you, Katie.

As always, thanks for your questions, and keep ‘em coming!

Further Reading:

What Happens to Your Body When… You Haven’t Properly Trained for Your Marathon?

Chronic Cardio 1, 2

Sprint for Your Health

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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29 thoughts on “Dear Mark: Running Across the U.S.”

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  1. Maybe she “Just felt like running”. Sorry, I had to throw that little Gump reference in there as that is the first thing that came to mind when I saw the “Run across the U.S.” title. 😉 I am going to assume that you have good personal reason for wanting to accomplish this feat so I do sincerely wish you the best of luck! It sounds extremely taxing on the body though so once you have accomplished your run, hopefully you will call it good. If its one thing that I have learned from Mark (ok, that isn’t fair as I have learned several things from Mark), it is that accomplishing feats of athletism doesn’t necesarily equate to health.

  2. The travel-by-foot feat has always charmed me. It goes on the “bucket list” with visiting all 7 continents, learning a second language, and writing a novel. Though, seems like the accomplishment lies in the distance, not the speed. If you (or any other apples out there) are interested in a more Primal north/south route instead of the east/west, I’ve heard the Appalachian trail is a pretty amazing trek, it covers over 2000 miles from Maine to Georgia.

  3. Mark- What about races/walks/runs for causes, such as the Susan G. Komen Race for the Cure? How would something like a 60-mile walk in 3 days affect the body? If trained correctly, would that actually emulate a Primal lifestyle? Or would it still be too much and have negative affects on one’s body?

  4. I’m very athletic and love to run. Years ago i was running too many miles and it started taking a toll on me. Running is great exercise but running too many miles was not. After cutting back from 9-10 miles a day to only 5 miles a day, i felt so much better. I just had to realize to pay attention to what my body was telling me. Running 5 miles a day is my limit. Every “body” has limitations.

  5. This post has inspired me to pick up a primal activity from my youth. Backpacking. It doesn’t get more primal than that. Growing up we would do 30-100 mile backpacking trips every summer. My father still does this but I havent gone with him in years. Next year, I think I will have too. Forgoing roads, walking in the woods and mountains, drinking water right out of the ground , carrying all of your food and clothing in a pack and sleeping in the great outdoors. Actually, it is starting to sound like the ultimate primal actvity!

    Hey Mark, how about a post on backpacking?

  6. Holly, a 60-mile walk in 3 days can be a totally primal, healthy, invigorating experience. In my upcoming book I talk about the concept of “renaissance fitness” which describes a type of overall fitness that allows you to take on any sort of challenge whenever you want…based entirely on how you train “Primally” from day-to-day. Low level aerobic activity, full-body-compound-exercise resistance training, and occasional sprints give you that kind of overall fitness. Just running 100 miles a week does not. Just lifting weights to body-build in the gym does not.

    Son and McFly, backpacking is very Primal. I remember doing a fair strecth of the Appalachian Trail during my college days. I bet you need a permit a year in advance to camp out on most trails these days.

  7. Detriment to her health aside, what an amazing goal! I wish her the best of luck, and lots of caution on the wellness front!

  8. I don’t know who has the time to do a cross country run. I can’t even take off long enough to drive across country.
    I’m sure she’ll recover if it’s just a one time thing. Doing it every year would be stressful.

  9. I can relate to Katie’s drive to go the distance… her question reignites my desire to hike the Pacific Crest Trail…. wouldn’t want to run it though. =)

  10. “The training, logic says, could be more damaging than the event itself.”

    The best take home point for anyone wanting to do endurance events. Nothing wrong with most events….it’s usually the overload of training that is 90% of the issue.

    Walking all day probably requires 4000-5000 cal, I couldn’t imagine the calorie intake needed to run.

  11. Thanks so much, Mark and others for your wise words and also encouragement. I learned so much, especially about the whole primal concept – amazing!

    Ok, so here is the real question. With all this advice, what DO I DO?

    Do I cover 20 miles a day on foot (running interspersed with walking) smartly…and can I recover afterwards? Or do I cover 20++ miles a day by a combo of things (run, walk, sprint, bike, hike)? The latter is basically the same, just the addition of the bike covers way more miles.

    I am still going to do this, I just need help figuring out a smart and healthy approach that does not seriously put my health in danger.

    Does anyone know of anyone who can offer some training advice?

    I love this blog! Thanks! Looking forward to your responses.


  12. My personal recomendation would be for you to go back to the 9-12 miles per day plan and walk it. 9-12 miles is very do-able walking per day. But I am no expert. If walking is an option with occasional sprinting, I think that would be ideal. That might defeat the prupose of your “Run” across America though. As Mark stated earlier, we still don’t know your motive, intention, time frame. More details would definity help!

  13. Hi everyone!

    Yes yes yes. More details are good;) So, I have wanted to run across the country ever since I was in high school, because I am passionate about running and it has shaped me in so many ways. More importantly, I wanted to do it for a cause and have it be mission-driven. I was searching for that cause, and it hit me last year when I was working with high school youth.

    I am doing this run to inspire people to LIVE THEIR DREAMS, and to LIVE more each and every day. This run is a way to carry and spread this message and example across the states, and to inspire as many people as possible, particularly youth. The idea is to empower youth along the way as well, and to host 5k races en route, details still in the works. The mission might sound simple, but it has so much meaning and personal connection.

    I am planning to leave this coming March, mid to late. I am doing this for sure.

    As for walking, hummmm. Thanks for the rec. I hope to have running in there somewhere!

    Here’s a thought – I could cover 20 miles a day, running half, walking half… (that is, taking walking breaks every 20 minutes or so as to mitigate damage). Can this run/walk/run/walk strategy mitigate damage?

    Thanks for putting up with all my questions! Really appreciate your help. Thank you thank you.


    1. I know this was a long time ago, but I’d love to hear how the event went, and if you were able to complete it. Any chance of an update?

      1. Her name is Katie Visco and she finished the run in Dec 2009. It took her 277 days (avg: 11 miles/day). She says the typical day was more like 15 miles, mostly running with a 1-2 miles of walking. She injured her knee near the end, and had to walk the last 2-3 wks. Doesn’t sound like she followed any of Mark’s advice – she mentions eating a lot of cliff bars and sandwiches every day.

        If you want more info, she has a Web site – just google her name.

  14. Hi Katie,
    I like your determination and i wish you all the best of success!

  15. Hi Katie!

    Hope my comment gets through this time and not bounced like the last one. Best of luck on your amazing adventure. Have you looked at the Crossfit Endurance website?

    They train people for endurance events (even ultradistance races) using Crossfit principles of high intensity interval training rather than the traditional long slow distance. Might be useful to you especially training up for your trip.

    Good luck!

  16. Katie, 20 miles a day can easily be done by walking. About 2-2.5mph is a decent backpacking pace, carrying 30lbs over uneven ground at altitude. So you should able to walk 3-4mph, which gives you around 5-7 hours of walking a day. Intersperse a bit of running to go faster.

    Run/walk is what most ultramarathoners do, and it’s definitely the best approach. See

    The running snobs call the run/walk Gallowalking, after Jeff Galloway (an Olympic marathoner) who advocates run/walk for most marathoners.
    Pay no attention to the running snobs, none of them are as fast as Jeff.

    I’d be inclined to treat the trip itself as training – start with 10-12 miles a day and work up, start running after a couple of weeks once hardened up. Use Mark’s Primal philosophies for your training right now, mixing up running with long hikes, weights or swimming, etc etc.

    Let us know where your blog will be, so we can see how it’s going 😉 best of luck.

    The comment on backpacking is right on the money – the hardest part of backpacking these days is getting the backcountry reservations..

  17. sorry this isn’t about marathons, but about the coconut article. How I wish that I could enjoy coconut again (like I did when a child). I am so allergic to it that I get vertigo in a minute after ingesting.

  18. Hey, I ran across the country 33 years ago. I’m OK. Just thankful to have shifted to a much better paradigm- paleo/primal. My achilles tendons are trashed, though.