0

votes

Best Duration and Interval for Fasting?

Answered on September 12, 2014
Created April 06, 2013 at 11:34 PM

What are your take on the interval and duration to use when fasting? I guess different fasts have different effects on the body. Anyone who has a first hand experience or some good research to share?

Note: You will have to have tried at least two different fasting intervals to be able to answer the question! To just mention that this or that interval worked doesn't really give any insight to which intervals work best.

32652cb696b75182cb121009ee4edea3

(5802)

on April 17, 2013
at 12:09 PM

Johan - there's more info in the book. I just grabbed a quick blurb. Basically, you can't directly translate mice hours/days to human hours/days. You don't want autophagy to stop. If you are fasting for this purpose, you want to fast while autophagy is high. If it slows down or stops, you lose the benefit.

6a8f63ea06241c38c03f22ef9344d517

on April 17, 2013
at 08:26 AM

The studies are english. This forum only have the links for the studies.

C5d5cfab77a26fa17a56f2c62b99b879

(542)

on April 17, 2013
at 08:09 AM

@Johan--Great point. As a scientific response, mine is not reliable because the effects of the diet and the exercise cannot be isolated from the effects of the chosen interval, especially since all three factors have remained constant over time. With that said, it would be remarkable--freakish even--in my unscientific opinion to get results this substantial this quickly selecting the least optimal interval frame. But who knows? Time will tell. I see already it won't be too long before I start to get gassed out at the gym or post-workout on the current interval. Thanks for the comment.

Medium avatar

(115)

on April 17, 2013
at 04:33 AM

Glad to hear about your progress in life! What you are doing seems to work for you. However it doesn't really bring any clarity to the question. You may have chosen the worst of intervals and we wouldn't know since it might all be a result of the paleo diet itself.

Medium avatar

(115)

on April 17, 2013
at 04:31 AM

since the site wasn't in English it is hard to see where I can gain the information asked for. Thanks anyway!

Medium avatar

(115)

on April 17, 2013
at 04:29 AM

... the whole day. So it seems that a 5 day fasting is better. Then it gets even more confusing when it says that it takes "several" more days to return to normal. So is it one day or several days? Whichever it is it still seems better than when fasting for 48 hours since then autophagy stops immediately.

Medium avatar

(115)

on April 17, 2013
at 04:26 AM

Thanks for your input. However, the following paragraph is very confusing: "Although long fasts do not upregulate autophagy, they do lead to a more exaggerated drop in autophagy upon resumption of feeding. Mice starved for forty-eight hours experience complete suppression of autophagy when feeding is resumed.17 In rats starved for five days, autophagy is completely eliminated throughout the first day of refeeding and takes several more days to return to normal." It says that after 48 hours of fasting, then when eating, autophagy stops immidiately. But after a 5 day fasting, it stops during

32652cb696b75182cb121009ee4edea3

(5802)

on April 08, 2013
at 04:54 PM

Here are the notes from the book if you really want to geek out: http://perfecthealthdiet.com/notes/#Ch40 Editing my original answer above to reflect the blurb from the book.

Medium avatar

(115)

on April 08, 2013
at 02:03 PM

any link? I seen research that shows that you don't get good autophagy/high ketone until 48 hours. http://paleohacks.com/questions/20247/does-intermittent-fasting-induce-ketosis

Frontpage book

Get FREE instant access to our Paleo For Beginners Guide & 15 FREE Recipes!

7 Answers

1
32652cb696b75182cb121009ee4edea3

(5802)

on April 07, 2013
at 12:27 PM

Here's one data point:

Perfect Health Diet has some graphs and data analysis that show a great benefit to the first 16 hours of a fast and decreasing benefits thereafter. The main thing they are tracking is autophagy (cellular house-cleaning for improved immunity, etc). For this reason they recommend the IF model of 16hr fast / 8 hr eating window. Not necessarily every day.

EDIT: The blurb from PHD (links to online studies in comment below):

"Many of the benefits of fasting appear to be triggered as the liver starts to run short of glycogen. The liver???s glycogen store is 70 to 100 grams, or about 300 to 400 calories. Since the body consumes 500 to 600 glucose calories per day, liver glycogen stores become low about twelve to sixteen hours into a fast... This suggests that a sixteen-hour fast is sufficiently long to trigger autophagy. Long fasts do not upregulate autophagy more than short fasts do. In mice, autophagy peaks within the first twenty-four hours of a fast and then drops back to normal levels within forty-eight hours of fasting. Possibly after twenty-four hours of fasting, cells become depleted of proteins, and continued high levels of autophagy would impair cellular function.16 Although long fasts do not upregulate autophagy, they do lead to a more exaggerated drop in autophagy upon resumption of feeding. Mice starved for forty-eight hours experience complete suppression of autophagy when feeding is resumed.17 In rats starved for five days, autophagy is completely eliminated throughout the first day of refeeding and takes several more days to return to normal."

EDIT 2: PHD does not have the graphs I was remembering; those are in Eat Stop Eat. He advocates a 24 hour fast at least once a week for these reasons:

-in first 24 hrs of fasting there is 70% reduction in insulin levels; the effect levels off after that

-a protein associated with fat burning (uncoupling protein-3) increases by 5 fold in the first 15 hours of a fast

-free fatty acids released to be burnt for fuel increase by 50% in first 24 hours of fast; effect levels off after that

PHD recommends limiting fasting to only 16 hours because this appears (from his analysis of the research, not mine) to be the "sweet spot" where the body doesn't freak out and try to make up for lost calories upon resumption of eating.

32652cb696b75182cb121009ee4edea3

(5802)

on April 08, 2013
at 04:54 PM

Here are the notes from the book if you really want to geek out: http://perfecthealthdiet.com/notes/#Ch40 Editing my original answer above to reflect the blurb from the book.

Medium avatar

(115)

on April 08, 2013
at 02:03 PM

any link? I seen research that shows that you don't get good autophagy/high ketone until 48 hours. http://paleohacks.com/questions/20247/does-intermittent-fasting-induce-ketosis

Medium avatar

(115)

on April 17, 2013
at 04:26 AM

Thanks for your input. However, the following paragraph is very confusing: "Although long fasts do not upregulate autophagy, they do lead to a more exaggerated drop in autophagy upon resumption of feeding. Mice starved for forty-eight hours experience complete suppression of autophagy when feeding is resumed.17 In rats starved for five days, autophagy is completely eliminated throughout the first day of refeeding and takes several more days to return to normal." It says that after 48 hours of fasting, then when eating, autophagy stops immidiately. But after a 5 day fasting, it stops during

Medium avatar

(115)

on April 17, 2013
at 04:29 AM

... the whole day. So it seems that a 5 day fasting is better. Then it gets even more confusing when it says that it takes "several" more days to return to normal. So is it one day or several days? Whichever it is it still seems better than when fasting for 48 hours since then autophagy stops immediately.

32652cb696b75182cb121009ee4edea3

(5802)

on April 17, 2013
at 12:09 PM

Johan - there's more info in the book. I just grabbed a quick blurb. Basically, you can't directly translate mice hours/days to human hours/days. You don't want autophagy to stop. If you are fasting for this purpose, you want to fast while autophagy is high. If it slows down or stops, you lose the benefit.

1
De1095b2ba29c1035f00428cbfe3cc7c

on April 07, 2013
at 11:17 AM

best listen to your own body, following any fixed fasting 'routine' is not natural or healthy imo

0
B6b2363b89dabe8ef39c071ed6c72dba

on May 10, 2013
at 02:59 PM

Lately I've been fasting (black coffee only) until lunch (protein/veg only; lettuce wraps or cheeseburger minus the bun), then protein/carb/veg/fat dinner at night, eaten within one hour. In about two weeks, have dropped three or four lbs and improved body comp after having stalled after six weeks of regular Paleo.

0
742028d147f580c347440bcab20dc641

on April 26, 2013
at 07:47 AM

One year ago, I did 'alternate day fasting' for a few weeks. I started with about 24 hours, a bit longer in practice due to sleep. That means, from late evening day 1 to early morning day 3. Later, I made it 36 hours, from 8 PM day 1 to 8 AM on day 3. Mostly to prevent overeating days 1 and 3, but also because I noticed you actually feel fitter this way.

0
C5d5cfab77a26fa17a56f2c62b99b879

on April 16, 2013
at 09:58 PM

After years on a straight SAD diet and zero exercise, I started paleo, IF and working out at the same time two months ago and have only good things to say about it. I can't quote actual weight loss because I haven't weighed myself before or since, but I went from size 35 to 32 jeans and lost pudge fat everywhere. If I had to guess I'd call it 25 pounds. I'm not jacked but for a 57-year old guy who just kicked a 30-year drug and alcohol addiction I'm put together pretty well, i.e., two-pack (not Tupac).

As a general rule, I eat in a 6 hour window and consume nothing else but coffee, tea and water during the other 18. Usually this will mean eating lunch at 2 and dinner by 8. I work out fasted, usually after fasting 14 hours or so. Weights and walking on alternate days with a resting day each week and a sprint session on a jump rope every now and then.

The fasted state does not seem to affect the ability to go hard at the gym (steady upward progress on squads/dead lifts, chins/pull ups, bench and shoulders) and I eat enough to never to feel hungry otherwise. On those occasions when I've felt hungry....I take a couple chugs of olive oil or a tablespoon of lard. It sounds weird but feels like just the right thing.

I eat a ton of food of all varieties, making sure I get lots of fat and protein. I have fruit and nuts maybe twice a week and completely avoid the paleo bad guys: grains (including rice), dairy, funky oils, sugars or sweeteners of any kind.

That's what works for me. I try not to be crazy about the fasting time frames so I can eat with friends and family on their schedule.

My general advice: keep the diet clean, fiddle around with fine points to find a happy point between your unique goals and total insanity.

Medium avatar

(115)

on April 17, 2013
at 04:33 AM

Glad to hear about your progress in life! What you are doing seems to work for you. However it doesn't really bring any clarity to the question. You may have chosen the worst of intervals and we wouldn't know since it might all be a result of the paleo diet itself.

C5d5cfab77a26fa17a56f2c62b99b879

(542)

on April 17, 2013
at 08:09 AM

@Johan--Great point. As a scientific response, mine is not reliable because the effects of the diet and the exercise cannot be isolated from the effects of the chosen interval, especially since all three factors have remained constant over time. With that said, it would be remarkable--freakish even--in my unscientific opinion to get results this substantial this quickly selecting the least optimal interval frame. But who knows? Time will tell. I see already it won't be too long before I start to get gassed out at the gym or post-workout on the current interval. Thanks for the comment.

0
6a8f63ea06241c38c03f22ef9344d517

on April 16, 2013
at 08:55 PM

I do daily fasting (16 to 19h).

Here you have many studies about fasting: http://www.hipertrofia.org/forum/topic/98266-seminario-de-bioquimica/

Medium avatar

(115)

on April 17, 2013
at 04:31 AM

since the site wasn't in English it is hard to see where I can gain the information asked for. Thanks anyway!

6a8f63ea06241c38c03f22ef9344d517

on April 17, 2013
at 08:26 AM

The studies are english. This forum only have the links for the studies.

0
4ae65e9a9abceabe4d2f6e2ccd810122

(50)

on April 07, 2013
at 01:35 PM

Depends on your energy expenditure. When I was lifting 3x a week and walking on off days, then 18 hr fasts daily and one 24 hr fast a week were fine.

Now that I crossfit 4x a week and kickbox 2 x a week, then I don't fast longer than 14 hrs per day.

This is what works for me. YMMV

Answer Question


Get FREE instant access to our
Paleo For Beginners Guide & 15 FREE Recipes!