Thursday, January 17, 2008

Fasting and Exercise

I've had a number of people ask me about the effects that fasting and exercise have on blood sugar.

In clinical research there generally isn't a concern that exercising while fasting will cause an ill effects to a persons blood sugar. The body is remarkably good at regulating blood sugar levels, even in the face of intense exercise.

In fact, most of the research on weight training and protein synthesis is conducted on people who have been fasted for anywhere between 12 and 16 hours. And, we know that there are professional athletes who play full NFL games in the fasted state.

However, as I have stated before, there is a difference between research and the real world. Most importantly, in research the people who participate as the subjects are always screened to make sure they are healthy, and that they do not have any underlying medical conditions that may effect the results of the study.

So, I figured this would be another great time to experiment on myself, using my dreaded glucometer.

After I was fasted for 22 hours, went to my Krav Maga class and took part in an hour of practicing leg kicks, body kicks and kicking and striking combinations. It was a hard class and I definitely sacrificed the health of my shins in the name of research!

Here are the results.

I started the class with a blood sugar of 4.7 mmol/L, pretty typical for me during fasting.

After an intense 15 minute warm-up of sprints, sprawls and various body weight exercises I retested by blood sugar and had a reading of 3.9 mmol/L (This is the lower end of normal, however I felt fine).

After the warm up we went right into shins kicks and defences with lots of moving around and striking, I was definitely sweating, and working hard, I took a quick break and tested my blood sugar which was at 5.6 mmol/L (This score is about the same as I would see after a meal)

We followed up with more pad work, throwing in some body kicks and more combinations and making sure our footwork was good, right at the end of the class I measured my blood sugar again and it was at 5.3 mmol/L (looks like I'm already returning to normal)

15 minutes after class my blood sugar was back down to 4.2 mmol/L. thirty minutes later it was 4.7 mmol/L and then right before my fast ended at 2 pm my blood sugar was 4.4 mmol/L. (Right back to where I should be. Time to eat.)

Just another example of the bodies ability to regulate blood sugar, even while fasted and exercising intensely.


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Anonymous said...

Diabetics may have a quirky response to exercising in a fasted state. I have read that our body's ability to inject glucose, or its equivalent into the blood stream may also be impaired. I have not tested this, but also experience a boost in BGs after heavy exercise, and am experimenting with a small dose of insulin before I lift weights. Rob

Anonymous said...


I did a similar thing last week, inspired by your previous test. First, I had tested after a workout at the end of a fast, and it was 114 (not sure the equivalent in your scale). So, the second time, I did it before I left for the gym, and upon my return. Before heading out, ot was 77 and upon the return, 101. Here's more detail that I posted in a comment at De Vany's site:

Brad Pilon said...

Hi Rob,

Yeah, Diabetics are an interesting bunch, from my experiences each one's physiology is different. They really need to know there own bodies.


Brad Pilon said...

Hi Mikoley,

your numbers are right in line with stayed within the "normal" range throughout your whole experiment.