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.
asked byJohan_Lindn (115)
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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.
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
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.
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.
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.
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/
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