Should we burn fat or glycogen when we run?

By Hayden Shearman

When you do an easy run, you’re primarily burning fat. When you do a workout or shorter race, you’re primarily burning glycogen. So, what’s best?

Not to disappoint right off the bat, but asking what’s best is probably the wrong question here, because the truth is that both energy systems have their place.

The easy-paced fat burning zone is great for teaching our bodies to fuel off abundant fat resources. This gives us a metabolic advantage when it comes to our abilities to go further in marathons and ultras.

On the other hand, glycogen is like rocket fuel. It’s awesome for running fast, but runs out fast, too. This is why we need to top it up in long races with energy drinks and gels, because it runs out after about 90 minutes even at marathon pace.

So, what’s better for weight loss?


Glycogen- and fat-burning zones both consume energy, which is what we’re after when weight loss is the goal. The glycolytic zone is extra good because when working at these higher intensities, the energy burning carries on beyond the time of exercising as it repairs and builds muscle from the intense work we just did. But the fat burning zone is good too, because we can do more of it.

So, it’s important that we have a good dose of both systems in our weekly training schedule. Not all high-intensity training and not all slow and easy. Mix it up. Keep it fun and interesting. And with this balanced approach, you should see the best results.