Glycogen depletion is the process of using up your glycogen stores. One reason to deplete glycogen is to increase fat burning. Because when less glycogen is available, your body has to tap into more body fat for energy.
To deplete glycogen, your carb intake must be less than the amount of glycogen you burn each day.
Carb Intake < Glycogen Usage = Glycogen Depletion
In other words, you have to eat very few carbs, exercise a lot, or both. As an example, let’s say you do 1 hour of cardio plus 1 hour of weight lifting per day.
From Table 1, we know cardio burns an average of 75 grams of carbs per hour. And weight lifting burns about 110 grams of carbs per hour. So that’s 185 grams of carbs per day through exercise.
For the rest of the day, we’ll say you have a desk job and only burn an additional 25 grams of carbs. That brings the total up to 200 grams of carbs per day.
Now, if you eat a relatively low carb diet of 150 grams per day, your glycogen will deplete at a rate of 50 grams per day. That means it would take 10 days to deplete 500 grams of glycogen.