High Carb vs. Keto: Which Diet Is Better For Endurance Athletes

EndurElite Chief Endurance Officer Matt Mosman compares the high carb to the keto diet, discusses what each is, how they produce energy during exercise, the pros and cons of each, and ultimately which diet is the best for runners, cyclists, OCR, and other endurance athletes.

 

Full Video Transcription:

Is A High Carbohydrate Diet Or The Ketogenic Diet Better For Athletes?

High carb diets versus the ketogenic diet, which is better for endurance athletes?

That is the can of worms we are gonna open today.

So over the last few years, carbs have really gotten a bad rap and there's a lot of fear-mongering around it saying they're bad for you. And on the other hand, the ketogenic diet is being hailed as the next holy grail of sports nutrition. 

So what we're gonna discuss today is what each diet entails, how it powers exercise, the pros, and cons of each.

We'll discuss a little bit of the research behind both diets as it relates to endurance performance and then we'll conclude with which is the best diet for endurance athletes. So let's get right to it. 

What Is Considered A High Carb Diet?

First off, the high carb diet. This usually entails eating about 40% to 60% of your total daily calories from carbohydrates. Now this range varies based on the intensity and duration of exercise on a daily and weekly basis.

So obviously if you're doing more miles, you're gonna require a higher percentage of carbohydrates. 

What Food Do You Eat On A High Carb Diet?

Now, typical foods you eat on a high carbohydrate diet are fruits, vegetables, grains, pasta, potato, basically everything that tastes good.

How Do Carbs Fuel Exercise?

Now the way high carbohydrate diets work to basically produce energy during endurance exercise is twofold. One, when you eat carbohydrates they can be stored as glycogen in the muscle.

And during exercise, this glycogen can be broken down into glucose and then, in turn, produce ATP to fuel the muscular contractions. 

The second way that carbohydrate powers endurance exercise is when you're consuming carbohydrate during running or cycling or any other endurance sport, it is converted to blood glucose, and again, that glucose can enter oxidated metabolism or anaerobic glycolysis where it can produce ATP or energy.

Pros/Cons Of A High Carb Diet

So what are the pros of a high carbohydrate diet? Well, the food is readily available, it's easy to get your hands on, it's probably the most efficient fuel for your muscles and the one it prefers, and additionally, it can be used by two energy systems in the body, anaerobic glycolysis, and then also oxidative metabolism. 

And interestingly enough, carb/glucose/glycogen is the only fuel source that can be used during anaerobic glycolysis.

As an example, when you're doing intervals or generally when you get over about 85% of maximum heart rate is when anaerobic glycolysis kind of starts to kick in. So that's a little bit of a brief background on a high carbohydrate diet. 

What Is Considered A Ketogenic Diet?

Let's move on to the ketogenic diet. Now let's get one thing straight right off the bat. A ketogenic diet is not a high-protein diet, it is a high-fat diet where about 80% of your total daily calories are coming from fat and then anywhere from 10% to 15% from protein and a very minuscule amount from carbohydrates.

What Foods Do You Eat On A Keto Diet?

Now examples of food you eat on a ketogenic diet are butter, things like avocados, nuts, coconut milk, fatty meats, basically anything that has a really high-fat content. 

How The Keto Diet Fuels Exercise

Now here's how the ketogenic diet powers endurance exercise. So when you're on a ketogenic diet, basically your glycogen levels become depleted and you don't have anything to use for a fuel source when it comes to that glycogen.

So what the body does is uses triglycerides or free fatty acids to power endurance exercise. And so what happens here is these free fatty acids are broken down into two ketone bodies, acetoacetate, and beta-hydroxybutyrate.

And these two compounds go through a few more changes where it's converted, excuse me, into something called acetyl-CoA. And from there it can enter the Krebs cycle where it can produce ATP or energy. 

The Pros/Cons Of The Keto Diet

So what are the pros of the ketogenetic diet and what are the cons? Well, the pros are is basically your triglyceride stores in your body even if you're super lean represents basically an unlimited fuel source.

That means to compare it to like a high carbohydrate diet where you can store about 400 to 1000 grams of glycogen in the muscle depending on how trained you are, the ketogenic diet and how much triglyceride you can store is way above that, again, it represents an unlimited fuel source. 

Now, what about the cons of the ketogenic diet? Well, the biggest con is those two ketone bodies, the acetoacetate, and the beta-hydroxybutyrate cannot enter anaerobic glycolysis.

So if you are on a ketogenic diet for that really low intensity, like, ultra-endurance type stuff, I could see a very big benefit for that.

But as you get into those higher intensity zones for heart rate, you are gonna fall flat on your ass when you go into anaerobic glycolysis if you are in a ketogenic diet and don't do any carb front loading before you hit like a hard effort. 

Say, for example, I know a lot of ultra-endurance athletes adhere to the ketogenic diet, but come race day they'll slam some sort of carb source before, like, a huge grind up a hill or before they hit a really fast section of the course where they're laying down some speed. So that's a brief kind of overview of the ketogenic diet. 

Which Diet Is Better For Athletes? High Carb Or Keto?

So what is the million dollar question? Which diet is better for endurance athletes? And we're gonna do this based solely on the research and I'm gonna add some of my opinions in here.

Based on the research, the high carbohydrate diet is king when it comes to endurance performance. Relatively speaking, there are thousands of papers that exist that have demonstrated the benefits of a high carbohydrate diet from anything from, you know, one mile run up to the ultra-endurance type events, there's no debating it. 

And in fact, I would say, like, carbohydrates have the biggest ergogenic impact or performance-enhancing benefits on your performance more than any other supplement we'll give you.

So hands down based on the research, the high carbohydrate diet is best for the endurance athlete. I mean show me any top-level endurance athlete who runs over two minutes up to the marathon that operates at a high intensity that runs well on a ketogenic diet?

They don't exist unless maybe they're, like, carb loading the night or carb loading during the race. 

When Is The Keto Diet Advantageous For Athletes?

Now I'm gonna be not too biased here and I'm gonna kind of present a fair overview of the ketogenic diet and where it may have potential benefits.

And that again is in the ultra-endurance crowd where you're operating at a fairly low intensity where you can still burn those triglycerides as a fuel source, you're not going into anaerobic glycolysis too often. That's really the benefit of the ketogenic diet. 

But even then there is not a ton of research on the ketogenic diet and endurance athletes. So I would like to see, you know, more and more studies coming out demonstrating that the ketogenic diet is the way to go for endurance athletes but I don't think it's gonna happen because you can't change the laws of physiology.

So again the high carbohydrate diet is the best diet for endurance athletes, I will debate anyone on that any day, any time, you name the time, you name the place.

A Word About Metabolic Efficiency/Flexibility

But I am gonna present one other option for you. For endurance athletes, if you kind of want to hit a middle ground between the high carbohydrate diet and the high fat and this is called metabolic efficiency.

And this is basically where you kind of decrease your carbohydrate consumption, I would say not to go below 40% and at the same time you up your fat intake from your diet and again go up to about 40%, so you're getting 40% of your total daily calories from carbohydrates and 40% from fats and the rest from protein.

And this will make your body possibly more metabolic efficient, meaning you may be able to burn fat up to a higher percentage of your maximum heart rate before it switches over to burning glucose and glycogen/carbohydrates. So that's something to consider. 

A guy named Bob Seebohar is kind of the expert on metabolic efficiency. So if you want to read more about that, just Google, search his name Bob Seebohar metabolic efficiency and Google.

So that is all I have today for the high carbohydrate diet versus the keto diet and which is better for endurance athletes. And by now we know the high carbohydrate diet is king. 

If you want other videos like this on endurance training, nutrition, and supplementation, subscribe to the EndurElite YouTube channel or head on over to the EndurElite blog at www.endurelite.com. Get social with us on Facebook and Instagram. And until next time, my endurance friends, stay fueled, stay focused, stay fast, and stay informed.

 

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