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Old 12-27-2007, 03:38 PM   #1
Susie Rosenberg
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Default My Understanding of IF

(Originally posted on the CF board; thought it might do some good here, also love to hear if I've gotten any of this wrong from those with more experience!)

I did a LOT of reading before jumping into this. From an MD's POV, here are my conclusions:

1. Nobody knows for sure what the ideal fasting "dose" is. Nobody knows the minimum number of days/week or fasting hours/day that nets you the purported benefits. Nobody knows, either, how much is too much if you are not starving yourself outright. Ideally, keeping records will provide the feedback necessary to evaluate any given individual's IF protocol. These records could include
-body weight and body composition
-lipid profile
-homocysteine levels
-performance records (max weights, metcon times)
-sleep hours and quality
-number of illnesses/month (colds, GI bugs, etc)

2. My understanding of why it works:
It's not calorie restriction, since most folks compress their daily calorie needs into a shorter feeding window. It seems to be related to two different processes. First, just giving the body a rest from the digestive process is like shutting off the engine of a car. The engine lasts longer because it is resting from the mechanical wear of moving parts, and the accumulated debris of increasingly dirty oil. (For us, that would mean less sludge in the arteries from not carrying around fat particles, and resting the cells from the work of digestion.) Basically, you are decreasing the rate of oxidation in the body (less rust!).

Second, fasting not only is a rest, it's a stress. When we stress, then rest our muscles, they get stronger. Apparently, when we fast, we impose a unique metabolic stress that also makes us stronger in a metabolic sense. We become primed to use food more efficiently. Our sensitivity to the actions of insulin increases---which means we need to put out less insulin to get the needed response. Hormones that have positive effects in our bodies increase: growth hormone increases, as do certain brain neuropeptides that are protective against Alzheimer's. Immunity to disease seems to strengthen as part of this neuroendocrine response to fasting. I haven't seen one study that reported negative effects. (Remember virtually ALL of these studies have been done on rats and other animals!)

Finally, from reading the animal studies, and the anecdotal reports of people who have been doing this, I've concluded the following about the risks and benefits:

1. Benefits could include: increased insulin sensitivity, decreased body fat, increased muscle mass, better immune functioning, decreased oxidation load meaning lowered risk of cancer and anti-aging effects.
2. Negative aspects: Some studies reported disturbance in sleep, which is why I asked about that in my original question. (Maybe it's only mice that don't sleep well hungry, because I had two really good nights' sleep fasting, and I don't usually sleep that well.) While the majority of people doing IF are happy with their strength gains, I gather if you are not careful about getting sufficient protein and calories to support lean body mass, you could lose muscle tissue. Also, some people respond to the fasting state with overfeeding and gain fat on IF; you have to be careful not to overdo it by telling yourself "I fast, therefore I (over)eat." Some people report that initially, metcon suffers. I don't really know what to say about that, 'cause I haven't gleaned what they did about it.


The science is compelling.

Susie
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Old 12-27-2007, 04:09 PM   #2
Garrett Smith
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Susie,
I'd comment, but I don't know what to say. From what I've read on IF (which to be honest, isn't much at all) and experienced on IF (been doing it for months now), everything you said above rings relatively true.

Personally, my hunch is that those who have trouble sleeping hungry is more of a mental thing, especially with relatively short (less than 24 hours) fasts. Or a significant magnesium deficiency.

I don't know of any folks who have gained significant bodyfat by "overfeeding" if they stuck to low-carb Paleo. If one gets into high starch/sugar foods to break the fast, Paleo or not, the insulin release plus the increased sensitivity makes for a big fat depositing party.

IMO, folks not eating enough is where most mistakes on IF are made, coupled with residual lack of insulin sensitivity from eating too many small meals a day leading to potentially rapid lean tissue loss, especially at the start.

Considering the carbs I had over Christmas, I was actually quite amazed at the ease with which I did a 24-hour fast yesterday (haven't done a full 24 in a long time). Sorry for the tangent, just had to say it, I guess.

Good post, I just don't know that you'll get much feedback here, if only because your thoughts were preaching to the choir...
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Old 12-27-2007, 04:28 PM   #3
Mike ODonnell
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I'll throw in my non-MD $0.02 although you probably hit most of the IF nail on the head.
Quote:
Originally Posted by Susie Rosenberg View Post
1. Nobody knows for sure what the ideal fasting "dose" is. Nobody knows the minimum number of days/week or fasting hours/day that nets you the purported benefits. Nobody knows, either, how much is too much if you are not starving yourself outright. Ideally, keeping records will provide the feedback necessary to evaluate any given individual's IF protocol.
I think minimum results have been touted at somewhere around fasts starting at 15 hours and not exceeding 24-36 for retained muscle. As little as 2x a week has shown great benefits to body composition but there is no proof that daily IF would give substantionally increased benefit. Everyone is individual in their daily recovery and performance needs as well as state of health, so tracking performance and health is important.

Quote:
2. My understanding of why it works:
It's not calorie restriction, since most folks compress their daily calorie needs into a shorter feeding window. It seems to be related to two different processes. First, just giving the body a rest from the digestive process is like shutting off the engine of a car. Basically, you are decreasing the rate of oxidation in the body (less rust!).

Second, fasting not only is a rest, it's a stress. When we stress, then rest our muscles, they get stronger. Apparently, when we fast, we impose a unique metabolic stress that also makes us stronger in a metabolic sense.
Nailed it there...although I would say IF is a modified sense of CR compared to a normal daily intake, as I now am able to keep muscle and performance on less daily calories than if I ate all day. One would guess that is due to increased macronutrient utlization through the stress periods that responds in a better uptake of nutrients and also improved/more efficient digestive process due to the "internal housecleaning" that occurs during fasting.

Quote:
1. Benefits could include: increased insulin sensitivity, decreased body fat, increased muscle mass, better immune functioning, decreased oxidation load meaning lowered risk of cancer and anti-aging effects.
2. Negative aspects: Some studies reported disturbance in sleep, which is why I asked about that in my original question. (Maybe it's only mice that don't sleep well hungry, because I had two really good nights' sleep fasting, and I don't usually sleep that well.) While the majority of people doing IF are happy with their strength gains, I gather if you are not careful about getting sufficient protein and calories to support lean body mass, you could lose muscle tissue. Also, some people respond to the fasting state with overfeeding and gain fat on IF; you have to be careful not to overdo it by telling yourself "I fast, therefore I (over)eat." Some people report that initially, metcon suffers. I don't really know what to say about that, 'cause I haven't gleaned what they did about it.
I would believe the #1 best aspect is the overall increase in insulin sensitivity that that has such a direct role in all aspects of fat gain, muscle gain, inflammation, ageing, disease risks and other health markers. Sleep I can say I have not had a problem with as I never go to bed "hungry". Muscle retention and performance of course is all about recovery, so if you don't eat enough to recover, negative aspects such as loss of muscle mass and performance will occur. If someone is overly active then perhaps on 2x a week IF is the best they can do. Eating alot in a short amount of time does take effort, but as your body utilizes those nutrients more you actually need less and get more bang for your buck. When in doubt...meat, fat and veggies seem to do the trick although knowing how your body responds and recovering from longer bouts of exercise (such as 2 hours of glycogen depleting ice hockey) will require a modified strategy that is only learned as you go along and realize what your insulin sensitivity may be and find your spillover point of carbs from muscle replenishment to fat.

All in all...like Dr G said...not many people will argue your valid points...I just throw in my thoughts because...well everyone knows I like to talk out loud anyways....at least until I get kicked out of here. lol....I think.

Very good synopsis!
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Old 12-27-2007, 04:40 PM   #4
Susie Rosenberg
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Thanks a bunch, that's exactly what I was looking for. I have a friend who is very, very active and I don't know what to tell him about how he might optimally integrate IF into his week without sacrificing performance, so i'm going to refer him to your reply here. Much appreciated.

Susie
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Old 12-27-2007, 04:40 PM   #5
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Quote:
Originally Posted by Garrett Smith View Post
Considering the carbs I had over Christmas, I was actually quite amazed at the ease with which I did a 24-hour fast yesterday (haven't done a full 24 in a long time). Sorry for the tangent, just had to say it, I guess.
With the quantity of junk I have eaten in my 5 days at my folks' house, IF is the only thing keeping my GI tract happy. 17 hour fasts, no problem.
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Old 12-27-2007, 11:15 PM   #6
Mike ODonnell
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Quote:
Originally Posted by Susie Rosenberg View Post
Thanks a bunch, that's exactly what I was looking for. I have a friend who is very, very active and I don't know what to tell him about how he might optimally integrate IF into his week without sacrificing performance, so i'm going to refer him to your reply here. Much appreciated.

Susie
When in doubt...integrate it in slowly...as in 1-2x per week....anyone that jumps into daily IF without judging recovery needs and knowing how to eat alot in a small period of time will only set themselves back. Start slow....mix it up....after all it is "Intermittent" fasting.....so there is no set schedule just by definition of the word itself!
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Old 12-29-2007, 11:06 AM   #7
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Great thread. Not much to add other than we KNOW a paleo type diet delivers pretty optimal performance. Joe Friel, USA triathalon coach remonds one, Barry Sears, Loren Cordain, Charles Poliquin...folks who make thier living coaching people and consulting recomend a very similar approach. Start with that then one can experiment with compresisng the feeding window, say from 12-18hrs of fasting, perhaps even jsut a day or two per week.
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