A couple of weeks ago, SteveL asked me in the comments:

“How would you fuel during a long run?”

Allow me to be a bit tongue-in-cheek here. If SteveL means what we usually do by “long run”—that is, a training run and not a race—my answer is, “with body fat and oxygen.” In other words, not at all.

The physiological details of this are best left to another post, but the short answer is this: the goal of a long run is not just to run for a long time, but to develop the system that helps us run long. Crucially, that system is known as the aerobic system, which you can think of as the system that burns fats in presence of oxygen.

Here’s the critical detail: the fat you eat doesn’t reach your bloodstream for a few hours. So, unless your long run is very long, any fats you ingest during the run aren’t really going to go towards fueling that run.

Let’s discuss the more conventional fuels people use on their long run (sugar-laden fuels such as a 3-6% carb solution or gels). Great for races, but I’ll get to that in a bit. If you ingest them during a training run, you’re enabling your body to lean on its sugar-burning energy system (which it uses for short-duration, high-intensity bouts) for a long time.  This means 3 things:

1. First and foremost, it enables your long run to be faster than is healthy: you’re liable to do what looks like a long run but is actually a bunch of short, medium/high-intensity training runs that in aggregate masquerade as a long run.
2. Because you’re fueled with sugar lets your aerobic (fat-burning) system off the hook , which is the system that is supposed to power your long run.
3. You’re using the short-duration, high-intensity (sugar-burning) system for a what should theoretically be a long-duration, low-intensity activity (which you’re effectively turning into a long-duration, medium/high intensity activity). You’ll wear your body down disproportionately.

To recap: no fuel for long training runs. Fats won’t help, and sugar is counterproductive.

(While the body does burn a mix of sugar and fat at all times, the longer the duration, the more fat should be in the mixture. Because the rate of fat-burning peaks at around 50-55% maximum work rate for most people, very long training sessions shouldn’t exceed this low intensity.)

Fueling during a race

Fueling during a race is different. You’re not trying to train anything here. You’re trying to get every bit of power you can from the machinery you’ve been developing in training, with the provisos that you (1) finish the race and (2) don’t blow the engine.

This means that you want to make sure you’re well-fueled (and you stay well-fueled) during a race. For anything that’s marathon length or below, fats still won’t help. For the vast majority of us, it’s still too short of a race. So, such races are the ones you want to approach with the run-of-the-mill advice on race fueling: your carb solutions and gels work great here.

There’s one consideration: don’t start fueling until you’re 20-30 minutes into the race. When your body isn’t already warmed up, it’s very easy for a shot of sugar to kick up your insulin levels, which reduces your fat-burning ability. But once you’re warmed up and burning fats at a high level, sugar has a much smaller effect.

 Fueling during an ultramarathon

Here’s where it gets tricky. There’s two sets of priorities to discuss: the physiological needs of the body and the practicality of fueling on the run.

The physiological needs:

• Hydration (water plus electrolytes)
• Nutrition (the right combination of macronutrients)
• Digestion (continued function of digestive system throughout the run).

The practicality of fueling on the run:

• Combining hydration with nutrition.
• Creating a food that fits easily through the valve of a handheld water bottle.

Here’s a drink recipe which (for me) meets all these criteria:

Basic Ultramarathon fuel 

Directions:

1. Add 1 cup of water into blender.
2. Add all ingredients (heavier ingredients first).
3. Blend on low until well-chopped.
4. Add the rest of the water.
5. Blend until smooth.

Nutritional Rationale

Timing:

For a recipe such as this, I usually drink one serving (about 42 oz) over a period of 2-3 hours. This generally takes care of both my fueling and hydration concerns.

This suggestion is a TEMPLATE for people to try out during training runs. It’s important to adapt this or any recipe, workout, training plan, or racing strategy to your personal needs.

Protein

The reason I like including sizeable portions of all 3 macronutrients (carbs, fats, and proteins), is to incentivize the body to maintain the digestive system activated in a low-key but comprehensive way. This applies for protein in particular: while protein will not go towards fueling the body during a race, I put a small amount of it in order to create a more balanced digestion process.

The same goes with fiber (occurring mostly in the spinach, blueberries, and chia seeds). Ultramarathoners are prone to cramps, indigestion, and other digestive issues during the race. By putting a small amount of natural fiber in here (not so much that it slows down digestion), we can help “smooth out” digestion during the race.

Electrolytes

As you’ll notice, one serving of this drink has a staggering amount of potassium (almost 1.3g) and a respectable amount of sodium (just over 0.13g). The reason I like this 10:1 ratio of potassium to sodium is because a lack of potassium is linked to muscle cramps, and reduced nervous system function. (This can lead to lower coordination and reaction time, which can cause an injury).

Generally speaking, more potassium is better (up to a point, of course). 130 mg of sodium every 2-3 of hours is quite enough to keep a well-adapted athlete going during a long race.

Carbs and fat

The sugar calories are straightforward: these will go towards topping off your glycogen tank, in order to stave off fatigue and help your aerobic engine continue to burn fats.

Now we get to the tricky bit. Supposing that you drink 1 serving of the recipe in 2 hours, you’re getting around 160 calories of carbs and 155 calories of fats an hour. You might think that’s not really a lot of carbs. However, that’s the reason a majority of the fats in the drink come from medium chain triglycerides (MCTs), sourced from coconut oil.

Why MCTs?

MCTs are relatively easy to digest relative to other fats, and they also become available for fat-burning very quickly upon hitting the bloodstream, helping to increase fat-burning and accelerating the metabolism. In other words, “reducing” the possible sugar content of this drink by balancing it out with coconut oil is an excellent strategy for endurance races.