Are you sure you want to run a marathon? Let’s talk about the Beginner and the Marathon.

female and male runners on a marathon

Photo by RUN 4 FFWPU on Pexels.com

A lot of new and novice runners get hooked with the desire to run a marathon. While admirable, a marathon is not a 5K, 10K or half marathon, and unlike those races this is probably biting off a lot more than one really wants to chew.

As an experienced runner, I didn’t dare attempt a marathon until I had been running seriously for a few years, and had already completed many races ranging in distance from the 5K to the Half Marathon.

For me, the marathon was far and away a much bigger physical challenge than even the half marathon. This is no surprise to most experienced runners, and even knowing that going in… the shock to my system was substantial and new.

To detail why the marathon is so much harder, let me go into some of the basic science behind how the body generates energy for running, how it impacts marathon training, and why it may present a beginner too steep a challenge training for a marathon:

(Standard caveat: I’m not going to cite any sources below. Documented research on all of the below is legion, across the internet. An internet search will provide you many references on all these topics, as will many running books.)

Distance running typically requires a combination of burning body fat and stored muscle glycogen. The greater the intensity of running, the more glycogen per mile that’s required to sustain the needed effort. For most, every mile of marathon intensity running will draw 60-70% of burned calories from glycogen, most of which is derived from consumed carbohydrates. Elites can call on a higher ratio of glycogen/mile while finishing marathons more quickly that most, usually in just over two hours.

Anyone who draws on less than 60% glycogen/mile is running at a very low (hint: very slow) intensity. Most of us draw on a 60-70% ratio while running at most intensities, including marathon paces. The ratio can go up to 100% at very intense effort levels (e.g. sprints and similarly hard running efforts)..

While the human body stores far more fat than you could ever hope to completely burn (3500 calories per pound of fat, and virtually all of us are carrying dozens of pounds of fat)… our relevant lower body running muscles can only hold about 1200-1500 calories of glycogen, and these stores cannot be renewed while actively working.

Fat burns at too glacial a pace to fully sustain most marathon-intensity running over the full distance. This is why, at anything beyond a walk or slow jog, the body mostly draws from glycogen for energy to sustain the running effort.

While the body has glycogen stored throughout, running basically can only utilize the glycogen in relevant lower body muscles. These stores are typically enough to last most experienced runners at a suitable marathon intensity for about 2-3 hours before running out. Once the body “bonks”, you slow dramatically and perceived effort becomes much greater. It’s possible to finish from there, but with great difficulty.

This is why such a big deal is made about marathon fueling. Virtually everyone needs to consume energy during the race to be able to finish it strong.

While it is possible to run an entire marathon without fueling, it requires running at an intensity and pace that’s much slower, one that most likely will require some stopping and walking throughout the effort. This allows a suitable portion of needed energy to be drawn from fat, since it offers enough time/space for glacially-burning fat stores to draw upon the needed energy.

You cannot teach the body to burn a higher portion of energy from fat at higher intensities. You can only improve the body’s fitness to a point where a given pace requires a lower intensity of your effort over time, and thus will draw more from fat.

This is what most ultra-marathon runners focus on developing during their training: To make a given pace/effort so easy that their bodies draw more from fat than glycogen. Ultra runners who swear by low-carb diets find over time that they burn more fat at a given pace over time… because their training paces become easier for their bodies to maintain over time.


So, why share all that info?

At any race distance shorter than 15-20 miles, it’s possible for a runner to finish the race without any additional fueling. Most marathoners in training have to develop a fueling strategy along with their overall fitness, because to finish the marathon at a desired pace they must take in additional glycogen to supplement their insufficient lower body stores.

Someone who hasn’t run before is much better off seeking to run a 5K or 10K than a marathon. They’re even better off trying to run a half marathon than a marathon, since the half is within that 15-20 mile threshold.

A new runner already faces an uphill training battle in building the overall fitness to race a new distance. Adding in the challenge of learning to fuel the balance of a race distance too long for anyone’s natural limits, let alone learning the mechanics of attending and running a formal race, is probably too much for a novice. and that never minds that untrained runners’ lower bodies probably store less potential glycogen than more highly trained runners. Their lower bodies’ glycogen stores will run out of gas sooner than an experienced marathoner.


If a rank beginner comes to me and says they want to run a marathon, my first objective is to persuade them to slow their roll and seek first to train for and run a 5K, a 10K, and eventually a half marathon before even beginning to train for a marathon. For them, training for and running a marathon at that stage would be physically akin to trying to perform surgery without even attending medical school first.

Yes, of course running a marathon from zero can be done, and people have certainly done it. Plenty of books exist with the theme of training for a marathon from scratch. It’s possible, especially with a run/walk strategy like Jeff Galloway’s. But, by and large, it’s not the most rewarding or satisfying path for people.


If you are brand new to running and absolutely want to run a marathon (plus, of course, you’ve consulted your doctor and are clear to exercise, blah blah blah), here is what I’d recommend.

  • Set your target marathon no less than one year in advance. Probably more than a year in advance.
  • If you aren’t already, I would start running regularly right now. At least a mile a day, 3-4 times a week, at an easy intensity/pace for you to sustain. You ideally should run probably longer than a mile per day, if you can handle it.
  • Focus on running at an easy, steady, sustainable pace for most if not all your runs. If you’re getting winded after a bit, you’re running too hard. Slow down.
  • General Tip that’s really beneficial in this situation: Join a weekly fun run. Running shoe stores often host these, though other groups also do weekly runs in parks. This will introduce you to other local runners, and you’d be surprised how many other runners are close to your experience level. You not only meet other like-minded runners, but many are helpful resources for advice.
  • If you ever do want to run faster, make sure the faster pace is steady and sustainable. Don’t sprint. You shouldn’t strain to maintain your pace in most training runs.
  • Each week, you should do a longer run than usual on the weekend. Try to get to at least 60 uninterrupted minutes of running on that weekend run. Each week, try to make the run a little longer than before.
  • Eat healthy food. Get 7+ hours of sleep each night. You should be doing this no matter what, but the positive/negative effects of diet and sleep are magnified when you run regularly.
  • Your goal for the next half year or so (at least the next 6 months) should be to train for and run at least two shorter races, if not more.
  • The last race you should run in that period should be a half marathon (or similar, like a 20K or 30K).
  • I would strongly recommend that the first race you train for and run be a 5K race. This shouldn’t take longer than 8-10 weeks of training, and your key training goal (aside from building the needed fitness) should be to get used to the schedule of training for a race, plus the mechanics of running in a formal race (which for a newcomer are honestly a bit complex).
  • After that, I would seek to run an 8K or 10K race, something that would take an hour for you to finish. Take 8-10 weeks to train for that as before.
  • You could just skip ahead and train for a half marathon, which usually requires about 10-14 weeks. But that’s a pretty big jump for your body. Proceed with caution. If your marathon goal is more than a year away, I’d highly recommend training for and running an 8K or 10K first, before trying a half.
  • While training for that 8K/10K, seek to stretch out your weekday runs so the duration of each is closer to the desired duration/distance of your goal race.
  • If you don’t already do so yet, consider trying easy runs of 30 minutes or more on back to back days during the week. It’s fine if you’d rather not and want a day off after every training run, but it can reap extra training benefits if your body handles it fine.
  • If you don’t already do it, I would also consider trying a speed run workout during the week. Speedwork triggers added neuromuscular development that will improve your running. Speedwork doesn’t need to be complex, something where your run is faster than usual, possibly short 1-2 minute runs that are pretty fast.
  • If desired, you can join a running group that does speed workouts during the week. This structured format and the presence of experienced coaches/runners can be very beneficial, especially if new to speedwork.
  • If you start doing speed workouts, make sure you take a day off before and after speed workouts, because these should be hard on your body.
  • If you can manage it, you should try to run another 5K race in the middle of training for that 8K/10K. Tip: If your town has a Parkrun or some other free weekend timed 5K run in a nearby park (do an internet search or talk to local runners to see what options are available), consider running that as often as you’re able. These often happen on a Saturday.
  • If you do a Parkrun or some other weekend timed run, don’t forget to run long and easy the following day, or even after the event if your body can handle it. You still need to do your long run!
  • If you want to strength train, then do it by all means. But try to keep it easy or stick to 2-3 days per week. While it’s good for general health and can help your runs, remember you need to reserve energy for your running. And too much overall training can produce injury and illness that can derail your training.
  • After the 10K, take a couple days off, then you can go ahead and train for a half marathon (13.1 miles) if desired. Again, this probably requires 10-14 weeks. it requires more time because building the aerobic and neuromuscular endurance to handle the longer distance requires more time for your body to adapt. The fitness gain needed for a 10K or 5K isn’t as substantially great.
  • At this stage, your regular weekday runs don’t need to get longer. One hour or so is a fine maximum. But your weekend long runs absolutely need to get longer. These long runs should be closer to two hours.
  • I’d highly encourage you to build up to running a bit beyond the 13 mile distance in long runs. The Half Marathon is right around where the body begins to push its natural single-run limits, so getting acquainted with long distance better prepares it to handle touching those limits. Plus, of course, if you eventually plan to run a marathon, it’s good to get some early practice running a bit longer.
  • Once you get beyond two hours running, you need to consider setting some maximums so you don’t burn out or get hurt. For most, a maximum time of 2.5 hours on a single long run is fine, especially if training for a Half. You can (and should) consider going beyond 2.5 hours once you begin full marathon training.
  • After running a Half Marathon, you should consider taking a full week off from running before continuing training. The recovery may actually develop your running fitness, as the body regains strength without any further breakdown from running.
  • After a half marathon training cycle, THEN I say it’s healthy and productive to begin training for a full marathon if desired.
  • Allow yourself 16-24 full weeks of training for your first marathon.

The great thing about observing all these bullet points, aside from gradually, sustainably building your fitness for a marathon… is that after all this you will know for sure whether or not you really want to run a marathon, or if the desire was a passing fancy.

Training this way gives you plenty of time and effort to change your mind, or realize that training is not the lifestyle you want. Barring that, it will build within you the running fitness to run a satisfying goal marathon on your terms.

To successfully run a race like a marathon, training for it has to be a lifestyle. It requires a lot of fitness development, a lot of positive habit forming. Anyone can randomly decide to run a 5K and manage to finish it. Anyone randomly deciding to run a marathon likely won’t come close to finishing.

Everyone I know who has in some way flaked on the needed training and development has paid the price on marathon day, if they even bothered to finish (which many did not).


Running a marathon is very challenging for the most experienced runners. Someone with little to no running experience faces an Everestian climb trying to train for a marathon. The best thing to do if you want to run a marathon but have little running experience… is to get that experience, by gradually training your way up through the shorter race distances. It will build within you the ability to run that marathon in a year or two, and possibly even have fun doing it.

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