Fueling your run

Gary Purdy PPTCHow to stay energized and endure is always a big topic of conversation in the running community. The truth is that there is more than one way to accomplish your goal. We are different and our bodies respond to nutritional input in varying ways, being subject to factors such as metabolism, genetics and current fitness levels. Nevertheless, the science of how the body uses calories is unquestioned, and having a true understanding of the science behind the madness may be the first step in discovering what will work best for you.

It's common knowledge that the chosen method for getting out there and conquering the beaten path is loading with carbohydrates; while this is a true and tested system, it’s only the beginning of the story. Carbohydrates are the chief source of energy for all body functions and muscular exertion, but there are a few key sources of energy, which provide different results.

Simple carbohydrates

Simple carbs, or single sugar units, found in foods like honey, fruit or juice, are quickly ingested into the blood stream and provide a quick boost of energy. The drawback to this instant energy is that your body produces insulin to remove excess sugar from the blood, causing low glucose (referred to as blood sugar). Low glucose levels can cause you to want more sugars, and potentially take in excess calories. For athletes or highly active people, sugars become advantageous during endurance based activity since there is a constant energy need, but when you have your sights set on those long runs, simple carbs alone won’t get the job done.

Complex carbohydrates

Complex carbs, on the other hand, are slow-burning carbs containing starch and fiber. Starch is transformed into glucose and burned as energy; fiber, which cannot be digested, is expelled from the body, but performs important tasks like regulating the body’s absorption of glucose. Good sources of complex carbs are whole wheat pasta, oatmeal and other grains, vegetables, whole grain bread, brown rice and sweet potatoes.

Since complex carbs burn slower than simple carbs, they are capable of providing sustained levels of energy and can prolong glycogen depletion. This is the reason behind “carbo loading”. When activity levels extend beyond 90 minutes, muscle-glycogen stores become spent, severely impacting performance and endurance levels. Supplementing these complex carbs with simple carbs like energy gels and drinks can fuel the body for extended periods of time, but the body will ultimately not be able to keep up with the demand to supply energy if you are running for several hours or more. This is when an alternate means of fuel becomes necessary.


Fats are the most concentrated form of energy. They yield 9 calories per gram in comparison to 4 grams for carbs and protein. Fat provides the main fuel source for long-duration, low-to-moderate intensity endurance sports like ultramarathons. Even during high-intensity exercise, where carbohydrates are the main fuel source, fat is needed to help access the stored carbohydrate. Converting stored body fat into energy takes a great deal of oxygen, so exercise intensity must decrease for this process to occur. For these reasons, athletes need to carefully time when they eat fat, how much they eat and the type of fat they eat. In general, it’s not a great idea to eat fat immediately before or during intense exercise.

There is a distinction between good and bad fat. Trans-fats (which are banned in New York) are linked to bad cholesterol and heart disease. These fats are found in margarine, shortening, fried foods, donuts, and many baked goods. Saturated fats, found in meat, poultry, and dairy, should be eaten in moderation. "Good fats" include mono- and poly-unsaturated fats; they are found in most nuts and seeds, omega-3 fatty acids from salmon, mackerel or sardines, flaxseeds, avocados, olive and canola oils.


We need fuel - and lots of it when involved in extended activity. A proper combination of simple sugars, complex carbs, and fats provides a stockpile of energy resources, helping you maintain glycogen stores and prolong energy depletion. And don't forget to replenish your electrolytes and water during your activity.

Try different combinations of carbs and fats to find the one that provides the best output.

Gary Purdy