Glycogen 101

Improperly managed glycogen is one of the leading reasons people ‘fail’ at weight loss. Glycogen plays a vital role in your journey, since it basically acts as the fuel-tank for your workouts and daily energy. And, if not properly managed, can result in feelings of total fatigue while you try to burn fat.

What is Glycogen?

Glycogen is basically glucose (sugar) that’s stored in your individual muscle cells. Glycogen provides the “fuel” for your muscles to operate. Imagine that each muscle cell in your body as its own individual fuel-tank, and glycogen is that fuel.

As you work your muscles (whether it’s from running, lifting weights, riding a bike, or any other high-intensity exercise) the glycogen “fuel-tanks” in your cells are rapidly emptied. They basically act as the front-line fuel source for high-intensity activity. (Fat from the food you eat, on the other hand, acts as the fuel source for l0w-intensity activity).

Where does glycogen come from?

There are two methods your body can use to fill the glycogen stores.  The most efficient method (since glycogen is basically stored glucose) is by converting the carbs you eat into glycogen and re-filling those stores.  A serious athlete doing 60 to 90 minutes of high-intensity exercise every day requires upwards of 300g of carbs in order to keep their glycogen stores topped off and keep their muscles functioning and peak efficiency.  (If you aren’t eating enough carbs to fuel the high-intensity workouts, your muscles are basically operating at reduced efficiency. In fact, if you eat too few carbs while trying to do high-intensity workouts, you’ll eventually fully deplete your glycogen and start feel completely fatigued, all the time).

Glycogen and Keto

But that’s not the whole story.. your body does have another (less efficient) way to produce glycogen.  If you completely starve your body of carbs (more than 2 or 3 days) your liver can actually produce small amounts of glycogen which your body can use for minimal amounts of energy needed.  It does this by converting fat to glucose, through a chemical process that’s not really important to understand for the purposes of this article.  Long story short — this is the premise behind ketogenic diets. Starve the body of carbs and as a result, force the liver to produce glycogen.

But there’s a down-side to this approach — namely, your liver actually can’t produce large amounts of glycogen without months (or sometimes even years) or careful training and practice. This is why most people who do high-intensity workouts find that a ketogenic diet leaves them feeling completely energy-deprived, while people who don’t exercise much (or at all) find that a ketogenic diet provides all the energy they could possibly need, despite eating almost no carbs.

What does all this have to do with weight loss?

If your glycogen stores aren’t sufficiently full during your weight loss journey, you’re likely to feel completely fatigued. All the time. You’ll still burn fat, but you won’t feel very good.

Complete fatigue while on a long-term keto diet is a good indication that your body isn’t producing enough glycogen. Carb-cycling is one possible solution, but you may also find that after being on a ketogenic diet for an exceptionally long time, your liver simply produces less glycogen that it once did.  The answer is to switch to a more traditional approach, allowing your body to get energy from carbs, rather than glycogen produced by the liver.  Some people, for whatever reason, can’t produce sufficient glucose on a low-carb diet no matter what, and report not feeling well after just a week or two on a low-carb diet. (Note that if you don’t feel well after 2 or 3 days, that’s normal, while your body makes the transition. This is sometimes called the ‘low carb flu‘).

People on a more traditional diet that also incorporate high-intensity cardio or strength training should pay careful attention to their overall carb intake. Eating too many carbs will make weight loss difficult, but not eating enough carbs will cause their workout performance to suffer, which will also cause weight-loss to stop. You’re looking for the goldilocks “just right” zone in terms of your total carb intake.  People who are restricting their carb intake while doing high-intensity exercise will also benefit from carb cycling, explained here.