T Nation

Restoring Glycogen

Let’s say someone with a first name that starts with “A” is on a low-carb diet. Now, this same person does some fasted cardio (let’s not turn this into a debate on fasted vs. non-fasted cardio please). Nothing serious, just a 30 minute walk at like 4 MPH; a brisk walk, really. Keep in mind, this is first thing in the morning. Roughly how many grams of carbs do you figure it would take to restore muscle and liver glycogen stores?

That would depend largely on your caloric intake the day before.

What is your diet like?

[quote]jdrannin1 wrote:
That would depend largely on your caloric intake the day before.

What is your diet like?[/quote]

<100g carbs

200g protein
~40g fat about 2/3 from fish oil

Around 1500 kcals/day

So basically, a very low calorie, low carb diet.

If you want to recovery the glycogen used during exercise then you’ll need to know how much you are actually using. Only a portion of the energy expenditure will actually be from carbs. Inevitably, not all carbs that you ingest will be used to resynthesize muscle glycogen, but assuming they are ingested during a hypoenergetic low-carb (meaning already glycogen depleted) and immediately post-walk, then this won’t factor in much. You’re still left with walking. Since you’re low-carb and likely glycogen depleted, and the cardio is fasted, you will burn more fat for fuel than under “normal” circumstances. I would presume the carbohydrate use during this walk will be almost insignificant. We’ll just say you use 20% energy from glycogen, and you burn 200 calories during the walk. You’re looking at 40 calories from glycogen, which equates to 10g of carbs. You would need to ingest and synthesize (assuming 100% efficiency) 10g of carbs to account for that lost during exercise.

Of course you would have to consider that had you not walked you would have used some amount of energy anyway, some of it coming from carbs. So if you’re concerned with having the level of muscle glycogen available (say for a lifting session) you would have had you not walked, then you’d have to take this into account. In the end it really doesn’t amount to much in the way of muscle glycogen depletion, unless you have extremely poor cardiovascular fitness or you are extremely overweight, in which case you may double the carbs used during exercise, which would still not amount to much overall.

EDIT: to clarify, under the conditions you listed you will likely not even burn the 10g of carbs in my example. The contribution to energy will probably be something like 5-10g, with the higher end of the range being for low fitness or post-refeed.