Brady Holmer

in between meals or you're fasting overnight and you wake up in the morning, like metabolic flexibility just reflects your ability to, you know, when glucose is low or glycogen stores are low, kind of switch over to using fatty acids or oxidizing fat for energy.

So you can use both fuel sources kind of interchangeably and use them well because you have like the cellular and metabolic machinery to do that.

But what it also means from a kind of performance and athletic perspective is that you're able to use fat as a fuel source at an increasingly higher intensity.

So most people may be aware that once you start exercising more at a higher and higher intensity, you use more carbohydrate or more glucose as an energy source compared to fat.

So if you read like a classic exercise physiology textbook, there's always this graph where

Exercise intensity is on the x-axis, and it goes from zero, which is resting, to 100, maximal intensity exercise.

And then on the y-axis is another zero to 100%, and that's your contribution of glucose and fat to your energy.

And so at rest, you're using almost 100%, maybe fat.

And as you increase your exercise intensity,

fat oxidation goes down, carbohydrate oxidation goes up, and then kind of in the middle, somewhere about 60, 70% of your maximum heart rate, that's where, you know, you're getting 50% contribution from carbohydrate, 50% from fat.

And so essentially, if you are a better fat burner, those are shifted a little bit.

So the slope of those lines is kind of reduced, whereas if

you know, maybe before your max fat oxidation occurred at 60% of your maximal exercise intensity.

Well, now, if I become a better fat burner, when I'm at 80% of my maximal exercise intensity, that's where my maximal fat oxidation occurs.

So you're using more fat at a higher exercise intensity.

That is kind of from a performance or an athletics exercise perspective, what it means to become a better fat burner.

And you can do that by doing fasted exercise.

You can do it by doing zone two, doing high intensity interval training, increasing your mitochondria, you know, eating a keto diet.

There's like the famous study where they looked at people habitually eating a ketogenic diet and their max fat oxidation was at 85% of their exercise intensity, which is kind of high.

So that's essentially what it means.