This topic was recently brought up and I wanted to create a wiki to discuss it.
So the question was brought up about wasted carbs. When you are done exercising, and you want to restore the muscle glycogen you used, what happens if your BG is high? Those are “wasted carbs”…
Step in to the way-back machine a little bit. From the days of urine testing, all you knew about your BG was if you were spilling sugar in your urine. If your BG is 160–180 mg/dl or perhaps a bit higher, your kidneys begin to excrete glucose in the urine. The sugar is not being metabolized, it is not being used. It’s basically just wasted. You are peeing it away. That’s what I mean by “wasted carbs”.
What does it take for your body to use the carbs you take in? If you have been paying attention for years, and you take insulin, you know the answer…insulin!
So if your BG is high after you finish exercise, and you are trying to restore the carbs, you aren’t doing it. You will just end up flushing those carbs down the toilet.
Here is an example. Suppose you finish at 95. Great! You take 2.0 units of insulin and 40 grams of carbs. After 30 minutes you have spiked to 200…
You know since you took 2.0 units, you got some of those carbs. But the ones that caused the spike are not being used by your body. You need sufficient insulin to metabolize the carbs. You are only able to use the ones below the threshold that caused your spike.
I always try to get a specific measure of carbs post-workout. The way I know for sure that I used all of them is to make sure I have taken a sufficient amount of insulin so that I do not see a spike after the carbs. And any low I have is just met with more carbs.
So a couple of key points:
If you are exercising below a certain intensity level, if you are primarily metabolizing fat instead of muscle glycogen, restoring carbs after exercise is not as important.
If you are only exercising occasionally, and your body has several days to restore muscle glycogen between exercise outings, you don’t need to do it immediately after you finish. You can do it over the course of the next day or so.
But if you want to exercise intensely on two consecutive days - restore immediately.
One of the things that is frequently overlooked by Endos and CDE type instructors - telling you to take insulin right after a workout. That’s crazy talk to them. But if you want to do it right, you need both carbs and sufficient insulin to metabolize those carbs. If your BG is low, then the carbs you take in following exercise are used, and you obviously don’t need insulin. But if your BG is high…you need sufficient insulin to use the carbs.
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