Wednesday, June 2, 2010
Update
Interesting new paper coming out soon in the journal Autophagy where extensive autophagy is observed in mouse neuronal tissue after only 24 hours of starvation. The authors even suggest that intermittent fasting would be therapeutic in view of their results. I'll jump the gun and add the pre-pub reference to the online book. While I'm at it, I'll fix a few typos too...
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I don't know if I'm too late to comment but I was wondering if you think I might be experiencing the benefits of protein cycling via my way of eating. I usually only eat one meal a day, usually at around 6pm and consisting of fairly high fat, moderate protein and fairly low to sometimes zero carbohydrates. I am having success losing body fat and gaining lean muscle mass and wist to continue doing this. Restricting protein seems counterintuitive when trying to gain muscle (according to BB websites) but seems to be working so far. I would be interested in your thoughts.
That would be a 24 hour interval, somewhat shorter than the 36 hour interval used in animal studies. Note that a one day protein fast with the last meal at 6 pm the day before ending with a breakfast at 6 am the day after is a 36 hour interval.
Not so fast!
Mice have metabolism that is ~7 times faster than human's (they eat ~25% of their weight daily). So, mice go into the ketosis of starvation after only 24h of fasting and they loose 10% of their body weight in this time. It will take about a week for an average healthy human to loose 10% of his weight (a month if he is obese). And it also takes about a week for a human to achieve the same level of ketosis.
So, to achieve the same level of autophagy as seen in a 24h-fasted mouse, a human would need to fast for about a week (ketosis is also known to upregulate autophagy).
You can google for references.
Frequent flier: we are talking protein here, not calories. A mouse likely has a similar nitrogen economy as humans in terms of loss from digestion and shedding and likely initiates autophagy in response to amino acid starvation in a comparable time frame.
I actually agree with FrequentFlyer. I tried 24-hr and 36-hr protein fasts for months, up to 3x a week and they did nothing for fat loss. Then I tried it for a week at a time (eating protein only once a week) and found weight finally went down.
Whether this is due to human's metabolic cycle being slower, I don't know, but it seems real autophagy didn't kick in until up to a week of protein restriction. This is of course, just in my case. Perhaps 24 and 36hr protein restriction is only mild autophagy and not enough to lower bodywide protein stores. In other words they are being replenished too often in humans as compared to other test animals.
Remember also that humans are huge compared to mice and we obviously have much more body mass for storage of proteins. Hence it may take longer for us to use that up as compared to a 250g mouse.
Here's some interesting info about how protein restriction may improve insulin resistance. Perhaps that's why some of us only see fat loss after longer protein restriction than 24 or 36 hrs.
When you see "starvation" in the text, substitute "protein restriction" and you'll see insulin resistance is perhaps a protective mechanism by cells in order to protect the body from overnutrition (too much protein, as that is the gauge the cells seem to use to see if adequate nutrition exists in the organism's environment).
http://www.ncbi.nlm.nih.gov/pubmed/19805130
remig said...: "we are talking protein here, not calories. A mouse likely has a similar nitrogen economy as humans in terms of loss from digestion and shedding and likely initiates autophagy in response to amino acid starvation in a comparable time frame."
I brought up weight loss comparison between humans and mice only to show the differences in metabolism. Many people do not realize how different metabolically is the state called ketosis of starvation from the normal fed state or even a ketogenic diet. Of course, autophagy is activated in full force then. For a human, fasting on water only, it will take about a week+ to reach this state. A mouse reaches it in 24h.
So, when people apply mice studies to humans, they tend to be too optimistic. A mouse is starving after 24h, more so after 48h (and on the 3rd day half of them die, while humans can last over 2 months without food.) Humans live off glyogen during the first 2 days of a fast. I believe they still have ample amount of protein floating in plasma then.
@gunther gatherer: protein cycling should not have effect on fat. At least I don't think so.
FrequentFaster, that is what I thought too. But then I tried it, and fat loss was the result. Very little muscle loss that I can see.
In addition, the indigenous tribes of Papua New Guinea seem to be extremely "ripped" and strong, with no loss of muscle tone, on a diet of only 3% to 5% protein.
Studies and theoretical analyses are useful to gain reference and to understand the mechanisms for how the body works, but second guessing metabolism is a "chump's game".
I have found your book today and have read it - thanks for the free online book! I do intermittent fasting 18/6 and will now do the Protein Cycling. I have a question though, you mentioned that "Two Days per Week Protein Cycling for those older than 40 yet younger than 50 or for those who feel that 24 hours of protein restriction is insufficient to induce autophagy." Would you recommend doing it 2 days in a row for a 42 year old female or alternate the days? I'd greatly appreciate your reply on this query. Thank you.
In the introduction of the book, you mentioned herbs that induce autophagy. Could you direct me to where it is located.
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