You Ate What?!

Duck Donuts

When it comes to exercising, many of us operate on this mentality: “I just ran 10 miles, so I can eat whatever I want today,” or “I just had a killer 60-minute workout, so it’s totally okay if I eat an entire sleeve of Thin Mints.”

Why do we do this? It’s because we’ve been taught that Caloric use and intake is simple math. “I burned 550 Calories during my workout today, so I can eat 550 Calories of whatever I want because now I’m in a deficit.” Calories from sugar aren’t the same as calories from meat; one does not equal or cancel out the other, and they are both metabolized differently. If counting calories were that easy, no one would struggle with weight problems.

I asked a friend of mine — a certified USATF running coach and a former endurance athlete — for his opinion on sports nutrition, since I’m no expert on the matter. He provided some great insight, and I’m excited to share it with all of you. Now, there’s a lot of information here, but spend some time reading his article. You’ll learn some new things, and Rick will challenge you (e.g., carbo-loading is unnecessary). I can’t wait to hear your feedback on this!

Too often as a coach you hear about what someone eats before, during, and after exercise. I swear that if I carried or ate what some people do in something as short as a 5K, I would weigh twice what I do now (which ain’t some sort of lightweight to start with)! So why is it that people feel that they need so much?

“Well, I’m exercising a lot today, which makes me hungry so I need to eat. Besides, I earned it!”

You earned it? Well, there is no doubt that exercising is great for countless reasons. Excess caloric burn may not be one of them.

Wait, what?

Yes, you heard me right. What a lot of newer endurance athletes (and heck, even veterans) don’t understand is that you may not burn as much as you think when you exercise! And even if you do, that does not mean that you have carte blanche to eat or drink like a pig.

Did you know that regardless of whether you run 5:00 miles or 12:00 miles that (in general) you will still burn approximately the same amount of calories per mile? On average, a typical male will burn in the range of 100–120 calories per mile, while the typical woman will burn in the range of 90–110. There is a variance based on weight, but these numbers are the accepted range. So that awesome 5K PR you just finished running? Well, the Clif Bar and Gatorade you picked up in the finishers area to celebrate just snuffed out your entire run. And never mind the pasta you will eat when you get home to “replenish” for the next run. You are now in caloric excess for the day (unless you aren’t eating or drinking anything else).

So, what do we do with this information? Well, let’s get a little technical and talk about the basics of fueling physiology to understand what type of nutrition you need to run effectively. You have three primary ways to get fuel into your body and each has its limitations. These are as follows:

  • The Phosphagen System. Think of this as the “nitrous boost” that some cars run off of for drag racing. You get a very limited boost for a very short duration. To be precise, you get about 5 to 7 seconds from this. It requires no oxygen use and is stored in limited supply. When you think of those Olympic 100m sprinters, this is their primary fuel source. The other way to think of it as the fuel for your fight or flight response.
  • The Glycolysis System. This is another non-oxygen requiring system, and as such, is also limited. It is also known as the anaerobic system. Once you cross your lactic threshold you primarily use this. And as the byproduct of this system is lactic acid, your body needs to clear it out of its system ASAP. You can only sustain this for about 2 minutes (+/- a minute or so depending on your individual physiology), as your body cannot process the lactic acid that fast.
  • The Aerobic System. This is the primary way you fuel your body, and the source of that fuel is glycogen. Simply put, this is sugar. The average person has about 1200 Calories of energy continuously stored in their body via their glycogen stores. If you were to run solely off of this storage, you could get somewhere in the range of 1–1.5 to 2 hours of fuel. However, there is more to it than that. When your body needs more aerobic fuel it will take fat stores, pull it into the liver (the organ that metabolizes everything), convert it to glycogen, and send it to the muscles. The problem: this takes a while. So, if you’re running at a higher intensity and burning through your glycogen stores, it’s going to take some time to convert the fat. As you continue along at a certain pace and those glycogen stores get depleted, you will need to slow down your pace to a balance point where the fat to glycogen conversion will keep up.  SIDE NOTE: Your brain runs COMPLETELY off of glycogen. You know what “bonking” feels like, right? It’s when you become light-headed, super emotional, your muscles shut down, and you get woozy. It means your brain isn’t getting the glycogen levels it needs, so it starts scavenging for itself. The rest of your body becomes second fiddle to preserve brain function.

Okay, so what? What am I supposed to do with that information? Work with me here. It’s coming next.

Through the natural process of training, eating, and sleeping, you will go through cycles of:

  • depleting glycogen stores and refilling them on the fuel-side, and
  • tearing muscle fibers and having them reform with more capillaries and mitochondria (a topic for a different discussion) on the muscular-side.

Proper nutrition is important to do both of those things, and a good mix of carbs, fat, and protein are needed. There are a gazillion sources of mixed information out there on what sort of ratios you should have for optimum performance, but the gist of it is to make sure you are getting some of each in your diet. Don’t waste the calories eating crap, because whatever your body doesn’t need to refill its glycogen stores it will convert to fat and store THAT instead.

This leads me to my next point: you cannot “carbo-load” the night before a race. In fact, you can’t in the days leading up to a race! Why? Because it only takes your normal diet to fill your glycogen stores, and once that level is reached, your body says, “Hey, we don’t need this. Liver, go convert this to fat and stick it in the fat cells in case we need it later!”

“But, but, but!! I’ve always been told to eat a lot the night before a race?” you might say. Yeah…by someone who doesn’t understand basic physiology. Through a well-written and periodized training plan, you will be heavily depleting your glycogen stores on a regular basis. Your body will naturally start to increase its ability to store more glycogen (to a certain point), and as you continue to train and get closer to race day, you will have gained a little bit of storage capacity compared to when you started the training plan. So what’s the bottom line for this? Continue to train and eat at the same rate. Increasing more as you get closer to your race will just store up more fat, which you do NOT want slowing you down.

“Alright, I can buy that even though it is not what the average runner seems to think. What next?”

Let’s wrap this up and talk about nutrition for training and racing armed with the knowledge from above.

Everyone is a little different on this one. If you are running/racing early in the day, you may not want to eat anything of substance. Exercising with food in your stomach diverts some of the blood flow to your stomach for digestion, which can hinder performance. If you have to eat something, keep it light and something that metabolizes fast (gels, shotblocks, fruits). Remember, you have more than enough glycogen stored in your body for a substantial amount of exercise, so you really don’t need anything, but some people just don’t like the feeling of being slightly hungry when they exercise. If you are running later in the day, try not to eat anything of substance within 3 hours or so before you run. I could never figure out in high school and early college why I couldn’t run anything longer than an hour or so without having stomach/bowel issues. Then, as I got older and more knowledgeable, I realized it was because we had lunch around 12:30 p.m. and practice was at 2:30 p.m. My stomach was still full and digesting!

First ask the question, “I am going for more than 90 minutes or so?” If your answer is “no,” then you don’t need anything. The only thing you may need is water if it is hot or you are reaching the longer side of that time. Over 90 minutes? At this point, you will want to have a strategy for refueling, and it should be something easy to eat and digest. There is a whole multi-billion dollar industry devoted to this, and everyone has different tastes. I was sponsored by Gu for four years as an amateur triathlete and love their stuff. It worked great for me. To keep it simple, you want to take in anywhere from 150–200 Calories an hour, which will allow you to top off your glycogen supply in real time. This prevents having to fully tap into your fat metabolization during exercise and gastric distress. You will need to drink accordingly. Once again, everyone is different and there is a way to calculate your sweat rate (see formula below).

Sweat Rate = (A + B) ÷ C 
A = Pre-exercise body weight – Post-exercise body weight, recorded in ounces. (1 lb. = 16 oz.)
B = Fluid Consumed during exercise, recorded in ounces. (1 cup = 8 oz; 1 gulp = about 1 oz)
C = Exercise Duration, recorded in hours. (40 min = .66 hr)

The key thing to remember in all of this is that you can NEVER replace in kind what you expend during the activity. It is simply not possible. Don’t try to eat and drink the same amount during your run that you think you are putting out.

Do not worry about electrolytes. You don’t need to take any in. Yes, this goes against the sports nutrition companies, but the reality is that you do NOT deplete electrolytes in sufficient amounts that they need to be replenished. You’re not getting cramps because you need electrolytes; you’re getting cramps because you are going harder than you are trained to or for the conditions. If you were truly depleted in electrolytes, every single muscle in your body being used would be cramping—not just your calves, hamstrings, or quads! Don’t fall into that myth.

One thing you DO need to be careful of is drinking just water during exercise and nothing else. If you are constantly drinking water and not taking in appropriate amounts of salt in some fashion, you will basically drown yourself. This condition is called “hyponatremia,” and you can read about it here. Hyponatremia can result in death, and has in running events when people overdid their fluid intake with pure water.

The critical time to get food back into your system is within the first hour or so. Take advantage of the body’s natural ability to replenish, but be sensible about it. If you ran 5 miles, you can go about your day and eat your normal meals. If you just finished a 20 miler in your marathon training, you’ll want to get in a combination of carbs and proteins to help rebuild those glycogen stores, and don’t forget to re-hydrate!

Run fast, run smart, and enjoy your health!

Rick Carter is a certified USATF running coach, and has more than 25 years of endurance sports experience starting from high school. He is a 9-time marathon finisher, including two Boston qualifying times and two Boston finishes. He has also raced and coached road cycling and triathlons throughout his endurance “career,” including two Ironman finishes (Florida and Lake Placid) and numerous other distances.


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