Category Archives: nutrition

A marathon dress rehearsal run, and discussing in-race fueling options

Yesterday’s 6 mile run wasn’t so much about training, because at this point of the taper I’m pretty much as trained as I’m going to get.

The goal of the run was to practice marathon fueling. Never minding that the Vancouver Marathon uses low-calorie Nuun as their electrolyte hydration at aid stations (which isn’t effective like Gatorade because Nuun is low calorie and the calories in Gatorade are important to avoid late-rate bonking)… even if they used a better solution, race mixed drinks are typically mixed on-site, often poorly so and leaving your cup short on the actual electrolyte solution.


If I haven’t effectively implied it, one of my primary race goals is to avoid hitting The Wall, the moment of 100% glycogen depletion when you bonk and just have nothing left in energy. I’m obviously not a marathon expert by any means, but anyone who says it’s unavoidable is wrong.

For those wondering why they hit the wall late in a race… pretty much every resource points to a lack of effective in-race fueling. Your body burns mostly carbs when running at any pace beyond a recovery jog, and the faster/harder you’re running the more proportionally you burn carbs. At my size I burn about 120 calories per mile run, and at over 26 miles, that’s over 3200 calories burned.

Despite my weight loss and fitness, I still carry a good portion of fat. But fat burns glacially in exercise compared to carbs. While you can train your body to proportionally burn more fat, your fat will never burn anywhere close to as fast as carbs will during a run. Carbs become glycogen, which is your body’s primary fuel during a run. No matter how much fat you have… as soon as you tap out your available glycogen, you bonk. You’re running on auxiliary power and your body acts like it. So I have to make sure I get enough carb fuel to offer a chance of avoiding the wall in the final miles.

(Yes, your pacing and general hydration are also factors, but those are far easier to control. And all of this never minds that no matter what I’m absolutely going to be very sore and tired in the later miles. I accept that.)

According to the Hansons’ fueling formulas, my lower body stores around 1200 calories of glycogen, and should burn about 1000-1200 calories of fat throughout the race. If I properly pace myself I need about 600-750 calories in pure carbs to finish the marathon without hitting the wall. I also should ideally do it frequently in smaller portions rather than every half hour or when I pass the aid stations.

Even if courses provide nutrition, your best bet is to carry this nutrition yourself and consume it regularly throughout the marathon (which adds the benefit of allowing you to pick nutrition that works best for you). Plus, I still need to be able to physically get myself to a food resource and then back to the hotel, so I’m better off overkilling a little bit on what I carry and consume since my effort doesn’t end at the finish line.

Since I’m not Eliud Kipchoge with custom engineered drink bottles waiting for me every 5K, and point to point van service for transport… I’ve needed to figure out what to carry with me. I only have so much space in a belt pack, and carrying a 32oz bottle of Gatorade will obviously slow me down more than it’s worth, as every extra pound you carry adds 3-5 seconds to your mile time. What I use has to work effectively, and be portable.

Over the last few months I’ve worked on in-race fueling on various runs. I’ve experimented with gels (one packet is 100 calories), chews (one 6-chew packet is 200 calories), honey (a full 6oz flask is 568 calories), and for a while made a go with the minimally viscuous raw agave in a gel flask (6oz = 485 calories).

The agave is portable and easily consumable, but its simple sugars only replenish certain glycogen stores (albeit important ones for the body, like in the liver) and aren’t fully utilized by the body to run. I still found myself fading or even bonking late in 2.5+ hour runs despite consuming it every 10-15 minutes in-run… whereas the more engineered electrolyte sugars of Gatorade and similar drinks did keep me going.

I have found Clif Shot Bloks useful, but there’s an obvious problem: Trying to chew and swallow something while actively running at a decent pace makes it a little hard to breathe, which in turn makes it hard to effectively run until you’ve swallowed (and hopefully washed down) a given blok.

And, as I’ve found out the hard way, you definitely need to chase anything you consume with water or the issue will become much more difficult. In a race that will already be very taxing, those little aggravations could more quickly exhaust my energy stores before the end of the race… which defeats the purpose of fueling in the first place.


So anyway, I sampled the shot bloks once again yesterday while carrying 20oz of water. Perhaps active water use after consumption would help. Perhaps practice would help. They are the easiest and least messy of my fueling options, and if I can make them work it’s a better solution than gel, which is not only really messy and tastes like flavored motor oil but doesn’t feel good in digestion. I took one blok every 10 minutes and washed it down after swallowing.

The good news is despite attacking Cricket Hill (up and down) three times during the run, I felt energized after the run as compared to tired (as I often am when I take a similar run after work). The issue remains that, even with water, the moments between the blok entering my mouth and when it finally goes down remain difficult for my breathing and in turn my running. My heart rate did spike the first 3 times I fueled but stayed level the subsequent times… but my pace wasn’t great relative to my active heart rate, and I suspect repeating this process 8-24 times could slow me down and further complicate an already complicated marathon situation.

Now, I could just do it anyway, which I think is not a bad Plan A given this is already going to be a difficult race, and having usable fuel for the haul that works is better than not having such fuel. I think no matter what I’m going to bring Shot Bloks for the race, and if no better method presents itself I will just suck it up and pop one every 10-15 minutes until I cross the finish line.

I can also consider loading up a gel flask with agave and carrying it as well, saving the Shot Bloks for every 30-60 minutes or so, and just taking the agave on the regular. Both sources are palatable and digest reasonably well, and (though I will want to attempt using them together at home or in training to make sure nothing happens) I think having an adequate supply of both will cover my fueling bases.

The race has an interesting (possibly Canadian?) wrinkle, supplying bananas to runners at an aid station around mile 19. Aside from the concern of runners recreating a Mario Kart course with discarded banana peels, I think taking and eating one at the opportunity would also help. Bananas are my most common post-run carb-replenish fuel, so digestion is no problem.

And of course I plan to stick to a pre-race ritual: Eating a breakfast sandwich and chasing it with a shot of espresso a couple hours before the race. The nutrition from this must be important: Every time I’ve done this, I’ve raced well.


Admittedly, a lot of the above is talk-it-through thought process on my part. I’ve given this a lot of thought, because being able to finish the race with dignity regardless of finishing time is a high priority for me, and I know fueling in-race is vital to that happening.