Thursday, November 06, 2008

Fasting, Exercise and Blood Sugar

Here are two quick "Did you knows?" concerning fasting, exercise and blood sugar.

Did you know that it takes 30 to 60 minutes of running at 75% of your V02 max (for conditioned runners) to get your blood insulin levels down to the same level found in people who have been fasting for 23 hours? (Dohm LG 1986)

Did you know that when scientists studied people who exercised after fasting for 23 hours, their blood sugar levels were actually found to be slightly higher then when the same people exercised after a small meal? (Coyle EF 1985; Dohm LG 1986)

What this means to you- running at 75% of your VO2 max for as long as 70 minutes in well trained runners who had been fasting for 23 hours did not cause hypolgycemia (low blood sugar) So if you like exercising while you are fasted, this research suggests you don't have to worry about hypoglycemia (as long as your exercise intensity isn't way above these levels).

And it takes between 30 and 60 minutes of running at a VO2 of 75% to get the same insulin lowering effect as simply sitting around the house after fasting for 18-24 hours.

Two things to think about the next time you are fasting.

BP

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9 comments:

Mary said...

Hi Brad,
I so appreciate your scientific approach to the information you share. I'm 16 hours into my fourth fast, and I can confirm the clearer, more alert feeling you get on a fast. Thanks for giving me something to think about for the next 8 hours of this fast!

Mary

Anonymous said...

As always those who are diabetic, (and note - many are undiagnosed) the issue is not merely high blood sugars, you system also has a deficit when it comes to low blood sugars. An hour of intense exercise - weightlifting and/or sprints usually spikes me, but once in a while those BGs plummet. A bummer. I test at the end of every session. RobLL

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Bob Garon II, IKFF said...

I'm curious then why, when I have trained certain folks who have not eaten in a while, feel like passing out and get the low blood sugar feeling?

Ryan said...

Hey Brad,

First off I want to say I love the information you've presented. I've followed IF (a more extreme version, I usually go 48 to 72 hours, with cardio mixed in after 36 hours) and have lost 22 pounds in three weeks. Thanks for the great research you do and arguing for what is natural and healthy, rather than cramming more supplement and eat,eat,eat propaganda down our throats. Love the blog. Keep up the great work!

Bob Garon II, IKFF said...

Ryan,

Aren't you concerned that you are eating up muscle while fasting that long?

Are you evaluating and keeping track of your weekly body fat percentage to ensure you are indeed losing what you want: fat?

I'm curious. Thanks

Anonymous said...

Hey Brad,

I'm curious to know your thoughts about fasting for people like me who are insulin-dependent, TypeII diabetics. Certainly if I were to talk to my nutritionist who specializes in diabetes, she would tell me to stay away for fasting. So I'm wondering if you've had or heard of successful users of your program who are diabetic. Thanks for your input.

Cheers,
Dan

Anonymous said...

Hey Brad,

I'm curious to know your thoughts about fasting for people like me who are insulin-dependent, TypeII diabetics. Certainly if I were to talk to my nutritionist who specializes in diabetes, she would tell me to stay away for fasting. So I'm wondering if you've had or heard of successful users of your program who are diabetic. Thanks for your input.

Cheers,
Dan

Anonymous said...

Hi Brad,

With all the research you do, you probably have read about Dr. Mark Mattson and the intermittent fasting experiments on mice conducted at the National Institutes of Health. The version of fasting - 24 hours every other day with ad lib feeding on days in between - seems to really have a lot of benefits, to include lowered blood glucose and insuling levels, and increased brain derived neurotrophic factor (BDNF). This article - http://www.sciencedaily.com/releases/2003/04/030429084013.htm - is a nice summary, very inspiring, and totally supporting the Eat Stop Eat version of intermittent fasting for health.

Take care.

Kels