Fat loading and endurance athletes

 If I were to ask what the most important macronutrient for physical activity is, I would probably get a wide variety of answers. Are carbohydrates the most important? They are our body's preferred energy source. What about fat? It could be argued that fats involvement in hormone balance contributes more in the long run. Protein? Certainly important for lean muscle development and maintenance. 

 

So, is there a right answer? 

In short, no. Each macronutrient plays an important role during physical activity, and each should be taken seriously as important aspects of athletic performance and recovery. 

But are there situations when one macronutrient would be more important than others? 

Now the answer is a little trickier. A nutrition student may actually have more trouble answering this question than others - we tend to overthink questions like these and try to analyze and solve them. This could be because of the questions wording. What if it were worded like this:

Are there situations when one macronutrient takes priority? 

 A little clearer, right? Now they questions is a little easier to answer. For example, competitive basketball players probably aren't going be eating a hamburger mid-game. What are they likely consuming? We've seen the commercials, they often are seen drinking a sports drink of some sort. Why? Because fast-digesting carbohydrates and electrolytes are required during an activity such as this; a basketball game is probably going to be relatively constant activity for over an hour. 

This brings us to the title of this article: Fat loading and endurance athletes. 

Carbohydrate loading is the dietary strategy that involves consuming large amounts of carbohydrates before a physically demanding activity (eg. marathon) in order to fully saturate your muscle glycogen stores to maximize energy availability during the activity. This is a common strategy, and fairly well-known and studied.

But what is fat loading? 

Well, it's in the name. Fat loading, similar to carbohydrate loading, is another strategy that involves consuming large amounts of fat in preparation for a physically demanding activity. It is much less common than carbohydrate loading, but it is used fairly often in ultra-endurance sports (i.e. triathalons). The major difference is that carbohydrate loading typically starts and ends 5-7 days prior to the event, whereas fat loading has been suggested to need to start up to a month before the event, and stay more or less consistent as the athletes primary dietary habit. The reason for this is that carbohydrate loading is more or less a strategy that involves eating specific food to store energy in the short term, whereas fat loading is a strategy to increase utilization of fat oxidation (using fat for energy), which is going to be used much more relevantly in endurance athletes that are consistently active for long periods of time. 

Endurance and ultra-endurance athletes are consistently active for a long duration. Marathon runners can be running for 2-5+ hours (depending on fitness level), and during this time the body will be using it's fat stores as a source of energy. Fat loading is a strategy that supposedly encourages your body to be more efficient at using these fat stores. It seems to make sense; the body uses fat stores during extremely long physically active duration, so consuming large amounts of fat should mean you have lots of energy.

Does it work?

Well, the science is still on the fence with this. There have been studies that endorse this method, and others that suggest, while energy sources are more in-line with an endurance athletes requirements, these athletes also experience less perceived energy levels due to the shift in macronutrient consumption (i.e. neglecting carbohydrates in favor of fat). 

So, is fat loading an effective way to prepare for a marathon? The short answer is: maybe... It is still not definitively clear whether or not this method actually holds any significant benefits for these athletes.

 I think the best answer to this question is this: each athletes needs to do what he/she can consistently maintain. If these athletes can't give up carbohydrates, or feel low on energy when fat loading, then they shouldn't try it. 

At the very least, it's an interesting topic, especially for these ultra endurance athletes, and something to consider for future studies.

 -CB

 

Burke, L.M., & Kiens, B. (2006). "Fat adaptation" for athletic performance: The nail in the coffin?. Journal of Applied Physiology, 100(1), 7-8.