1

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A few fasting questions

Answered on August 19, 2014
Created June 10, 2012 at 12:19 PM

Hi there. Does anyone have any scientific evidence showing how long it takes before the body becomes catabolic (starvation mode) - is it 16 hours or more like 40? Also many people insist on eating caloric sources while fasting like coconut oil. What do you think of this? Is it necessary? If so, what other caloric sources could be acceptable while fasting? Any scientific articles would be much appreciated!

4dc97234de5ef4ebe77c78323d527bd0

(183)

on November 15, 2012
at 03:08 AM

I fasted for several years. Then I ran into a perfect storm of life stressors & got burned out - possibly adrenal fatigue. The fasting might have contributed as well, though I have chronic insomnia so who knows. So now I warn people to keep in mind that you are taking advantage of a beneficial stress response, and only do it if you have a low-stress life.

93eea7754e6e94b6085dbabbb48c0bb7

on June 12, 2012
at 03:25 AM

So what does this mean in terms of starvation mode and do you yourself fast?

3ab5e1b9eba22a071f653330b7fc9579

(2262)

on June 11, 2012
at 11:10 PM

Thanks for the help Adam!

631b29d5ab1146e264e91d08103bb72c

(1277)

on June 11, 2012
at 08:01 PM

More info on other fasting questions: http://www.leangains.com/2010/10/top-ten-fasting-myths-debunked.html

631b29d5ab1146e264e91d08103bb72c

(1277)

on June 11, 2012
at 08:00 PM

http://www.ncbi.nlm.nih.gov/pubmed/3661473

3ab5e1b9eba22a071f653330b7fc9579

(2262)

on June 10, 2012
at 06:43 PM

To be honest, I do not have a specific source that says this because when i first started fasting I read every blog, webpage, and book I could get my hands on on the subject

93eea7754e6e94b6085dbabbb48c0bb7

on June 10, 2012
at 01:26 PM

Thanks for the feedback! Do you have a source thst says its 72 hours?

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5 Answers

best answer

1
4dc97234de5ef4ebe77c78323d527bd0

(183)

on June 11, 2012
at 07:46 PM

There isn't a specific "starvation mode" biomarker - different body systems have different type scales. And for each, there is a graph of response over time, and usually there isn't a predefined level that's "starvation mode". So you have to look at the graph and pick a "corner" point. The best data I've seen is from Brad Pilon's book "Eat Stop Eat". To summarize:

  • For plasma insulin levels, there isn't a clear corner, but 70% of reduction occurs in the first 24 hours. IT drops rapidly for about 20 hours, then slows down (though continues dropping) through 48 hours.
  • For increase is plasma free fatty acids (indicating the body has switched to fat burning), the big jump is between 16 and 24 hours. Then it levels off. (Though Brad's graph doesn't have data from 3 to 12 hours).
  • Expression of UCP3 (a marker of fat burning) goes up by 5x from 3 to 15 hours, and by another 2-3x from 15 to 40 hours.

Another good source of data is Dr. Johnson's Up Day Down Day diet book, about alternate-day calorie restriction. His data is about duration of doing IF, not per-fast duration, but it's still interesting. To summarize:

  • Peak expiratory flow for asthma patients (a measure of inflammation) improved steadily for the first 3 weeks, then was flat.
  • Mood and energy showed the same pattern.
  • Nitrotyrosine levels, a measure of oxidative stress, dropped by 50% after 2 weeks, dropped by another 75% (so about 1/8th of original) after 4 weeks, and dropped a little more by 8 weeks, down to 1/10th of original.
  • Concentrations of TNF (Tumor Necrosis Factor alpha), one of the most commonly used measures of activation, dropped slightly after 2 weeks, moderately after 4 weeks (way down on fast days, only moderately down on up days), and dropped to about 1/4 of original levels on both up & down days by 8 weeks.
  • Concentrations of BDNF (another inflammation marker) dropped steadily over the first 4 weeks, then were flat.

Hope this helps.

93eea7754e6e94b6085dbabbb48c0bb7

on June 12, 2012
at 03:25 AM

So what does this mean in terms of starvation mode and do you yourself fast?

4dc97234de5ef4ebe77c78323d527bd0

(183)

on November 15, 2012
at 03:08 AM

I fasted for several years. Then I ran into a perfect storm of life stressors & got burned out - possibly adrenal fatigue. The fasting might have contributed as well, though I have chronic insomnia so who knows. So now I warn people to keep in mind that you are taking advantage of a beneficial stress response, and only do it if you have a low-stress life.

1
211d4075d68b24cd0aa7ebfa94262bb9

on June 10, 2012
at 06:10 PM

Even if you remain sedentary during a fast your glycogen stores will be depleted within about 14 hours. After that your liver and kidneys will have to synthesize glucose from catabolized muscle tissue.

http://www.medbio.info/Horn/Time%203-4/homeostasis1.htm

1
Dfe1dfb34939145fe21b3d8fa6832365

on June 10, 2012
at 12:53 PM

Fasting is a catobolic state. How long you can fast before you start eating into muscle tissue depends on macronutrient intake, caloric intake, how adapted your body is to burning fat and fasting, hormones like Growth Hormone, etc. By this I mean, best case scenario: Your glycogen stores are full, you've got a healthy amount of bodyfat, you're fully adapted to fat burning and a fasted state, and you've got awesome hormones. In my opinion you'd be able to fast quite a while before breaking down large amounts of muscle.

I saw calories as necessary for comfort during the initial adaptation phase. Once I was adapted, eating became counterproductive, especially carbs since they inhibit fat burning to at least some degree.

Brad Pilon has some good information about the things you asked. His videos can be found on youtube.

0
C3bc92e6b5eba45dc55f43ac3c70cc25

on July 05, 2012
at 01:56 PM

Leangains.com has an article that cited 36 hours & up will result in loss of muscle. Sorry I dont have a link (I'm on my cellphone) but I believe it's in the FASTING MYTHS article.

0
3ab5e1b9eba22a071f653330b7fc9579

on June 10, 2012
at 01:16 PM

It is actually about 72 from my understanding, if course there is always a little catabolism with fasting, but the effect is minimal until about the 3rd day. I have done 40+hour fasts with no problems whatsoever

93eea7754e6e94b6085dbabbb48c0bb7

on June 10, 2012
at 01:26 PM

Thanks for the feedback! Do you have a source thst says its 72 hours?

631b29d5ab1146e264e91d08103bb72c

(1277)

on June 11, 2012
at 08:00 PM

http://www.ncbi.nlm.nih.gov/pubmed/3661473

3ab5e1b9eba22a071f653330b7fc9579

(2262)

on June 10, 2012
at 06:43 PM

To be honest, I do not have a specific source that says this because when i first started fasting I read every blog, webpage, and book I could get my hands on on the subject

631b29d5ab1146e264e91d08103bb72c

(1277)

on June 11, 2012
at 08:01 PM

More info on other fasting questions: http://www.leangains.com/2010/10/top-ten-fasting-myths-debunked.html

3ab5e1b9eba22a071f653330b7fc9579

(2262)

on June 11, 2012
at 11:10 PM

Thanks for the help Adam!

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