Nutrition for Runners: Carbohydrates, Protein, and Fat

Carbs, protein, and fat all in a convenient hand-held design!

Thank you for your initial comments to my introduction to this series about nutrition for runners. It’s a big topic! I appreciate that many of you carefully and consciously consider your eating choices and, in particular, how they affect your performance before, during, and after races.

Food is sometimes comfort, sometimes entertainment, sometimes simply a sensory delight! However, at its essence food is fuel, especially for runners. What we eat provides the energy we need to run, recover, think, and live. Before we get into the nitty-gritty of what foods we should eat to optimize our running performance, it’s first and foremost important for us to understand how food actually fuels us.

The foods we eat contain three types of fuel within them: 1) carbohydrates; 2) protein; and 3) fat. Each plays a role in producing the energy we need to sustain our physical activities as well as actually building our physical bodies. This article is not intended to provide in-depth understanding of the various metabolic or chemical processes needed for energy-production, but rather for you to understand that carbohydrates, protein, and fat each have their purpose and importance in intensity, duration, and performance. So, let’s start with the basics. 

Macronutrients and Micronutrients

Before we get into the differences between them, it’s helpful to understand how carbohydrates, protein, and fat compare to other nutrients in food. These three types of fuel in our food are “macronutrients,” meaning that the body needs relatively large amounts of each. In addition to these macronutrients, foods also contain “micronutrients,” which are things like vitamins and minerals. So macronutrients fuel us and we need to eat relatively large quantities of them, and micronutrients are the vitamins and minerals we need in relatively small quantities for optimum health.

All the beautiful carbs at the market in Taiwan.
All the beautiful carbs at the market in Taiwan.


There are two major types of carbohydrates: simple and complex. Simple, or refined, carbs include sugar, cakes, cookies, white breads, and most fruits. Complex carbs are whole grains and other foods that contain a lot of fiber like many root vegetables.

Simple carbs get into our system very quickly and tend to raise insulin levels, which can contribute to diabetes if consumed in excess over time. Simple carbs sound bad, but as runners they are a very important tool to improve performance. Most energy gels and sports drinks contain simple carbs which are needed in long hard efforts to prevent bonking by providing an instantly useable energy source for your body!

Complex carbs, on the other hand, contain more fiber than simple carbs, and must first be broken down by your body into simple sugars before they can be used for energy. This extra step means slower absorption of carbohydrates and as a result, they are more filling than simple sugars and provide a more level energy stream. This, however, makes complex carbs a nonoptimal tool for a mid-race boost.

Carbohydrates provide the most readily available form of energy to fuel endurance exercise. Our bodies can burn off carbohydrates upon ingestion or store the excess as glycogen in our muscles or fat. Glycogen is our muscles’ primary fuel. During very long hard efforts, like racing a marathon, we need to refuel with carbs while running because our muscles cannot store enough in them to make it through the race.

Outside of performing, complex carbs are a better option. They not only contain the carbohydrates we need to replenish the glycogen we burn on our training runs, they also contain many more of those micronutrients than simple carbs that we need for optimal health. The historical rule is that 45-55 or maybe even 60% of our calorie consumption should come from carbohydrates, preferably complex carbohydrates. We’ll see later how some are challenging this long-held belief.

Great sources of protein, Japanese-style.
Great sources of protein, Japanese-style.


Protein is an important component of every cell in our body. Our bodies use protein to build and repair tissues. We use protein to make enzymes, hormones, and other body chemicals and it is an important building block of bones, muscles, cartilage, skin, and blood. Unlike carbohydrates and fats, however, the body doesn’t store protein. Endurance athletes require quality proteins to build, maintain, and repair muscle fibers damaged during our daily exercises, to help injuries heal promptly, and, among other functions, to meet energy needs in the latter stages of ultra-endurance events. Consuming high-protein foods has many benefits for athletes, including:

  • Speeding recovery after exercise
  • Reducing muscle loss
  • Building lean muscle
  • Helping maintain a healthy weight
  • Curbing hunger


Fats provide our body with energy; stored fat is what the body relies on when carbohydrates for energy are depleted. It provides more than twice as much as energy as equivalent amounts of protein or carbohydrates. It helps move some micronutrients like vitamins A, D, E, and K through our bloodstream and absorb them into our body and provides the linoleic acid needed for growth and healthy skin and hair. Fat also provides insulation for body temperature regulation. Essential fatty acids play a role in brain development, blood clotting, and managing inflammation.

A thorough discussion of “good” vs. “bad” fats and their potential relationship, causal or otherwise, to certain diseases could take pages or even an entire book! Suffice it say that avoiding definitely unhealthy transfats (i.e. partially hydrogenated oils) in favor of healthy fats such as avocados, olives, nuts, salmon, or grass-fed beef should help meet a runner’s high energy needs without any potentially adverse health effects.

So that is some background information about macronutrients, or the fuel in our food: carbohydrates, protein, and fat. I look forward to digging a little deeper into running nutrition next time.

Do you have any questions about carbs, protein, or fats? What are your favorite forms of each food fuel source?

I'm a senior masters runner. I write about my running journey and topics of interest to runners of all ages. My current goal is to maintain of steady base of road and (new to me) trail running, with some 5k, 10k, and half marathons throughout the year.

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  1. This was a really helpful article! I know I’ve read tons and tons about nutrition for runners, but every time I’m re-focusing my nutrition at the beginning of a training cycle, I need these reminders about WHY I’m doing what I’m doing 🙂 I’ve always aimed for 40% Carbs/ 40% Protein/ 20% fat. You mentioned 55 to even 60% carbs, which I know obviously isn’t a one size fits all recommendation, but I’m curious what the other macro breakdown would be if I did 55% carbs- would I do even distribution of fats and proteins then? Just curious what you think!

  2. For nutrition newbies, I would also add to the micronutrient vs macronutrient section that macronutrients are what provide calories: carbohydrates and protein provide 4 calories per gram, and fat provides 9. I’m excited to see where this series goes!

    1. I think that point is really important- knowing where the calories are coming from and what foods are giving you more from a specific macro. When I try and analyze my diet at the beginning of a training cycle, I first try and get a good gauge of where I’m going over/under on those numbers. Oddly enough, I’d have assumed I eat more carbs, but I eat more fat than I realize sometimes!

  3. Thanks, Sage. I’m about to start a new marathon training cycle, and my nutrition isn’t something that I’ve kept a close eye on as a part of training. Looking forward to reading more!