Susie Rosenberg
12-27-2007, 02:38 PM
(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
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