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New here! Questions on defining CR and biomarkers for successful CR.


GenGenimney

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I'm interested partially in CR because I have a rare, possibly undocumented metabolic or channelopathic dominant genetic disorder (neuro and I have different bets on which it is--I'm betting channelopathy, and he's got his bets on mitochondrial metabolic--dominant metabolic disorders are just so insanely rare, though) that has been drastically improved in the past when my food intake has been low.

 

I've never been clinically underweight, but until the most recent kid, I've bopped between a BMI 18.5 and 22, depending on a lot of things.  On CR--never more than a few months to a year at a time in the past--I've usually been 18.5-19, 19.5.  Below a BMI of 20, my body temperature drops measurably (to the point that nurses think they're measuring wrong--it's been 96.8 orally pretty often).  My blood pressure is also always low but rather dramatically so when I have a lower BMI--I've seen 85/57, and it's rarely, rarely above 100/70.  (Nurses usually quip, "Are you alive?")  

 

When I got fat (juuust over a BMI of 25), both my blood pressure and my temperature were more normal--blood pressure 110-115/whatever (sorry, don't remember), temperature 98.6 (on digital oral devices that "fix" the set point to 98.6 for average people), which I'd never seen before.

 

I've been restricting to lose weight first (to get back to where I'm healthiest) for about 2 months (after having dropped quit a bit in the previous several moths), and I've dropped my body temp by .3 degrees F already.  Haven't checked BP, but my heart rate is down 30-31 BPM from where it was.

 

According to the CRON calculator, I did a 50% restriction for a month (YES, it was safe--I lost 2lbs a week, and I stayed above 1000 calories a day, making up the rest with exercise) and am now at 40% (still safe!).  I'm not hungry at 40% but my maintenance weight would end up unacceptably--lethally--low.

 

Which leads me to my points of confusion....

 

1.   The idea of CR being based on ab lib personal "normal" doesn't make any sense at all to me.  What if I was over-eating before?  What if I were a chronic under-eater?

 

2.  The idea of a body-double makes much more sense, but TDEE on the calculator here activity into account on the % restriction, and other studies haven't shown the benefits of exercise-caused deficit to be the same as CR-based deficit....

 

3.  And all restriction would create a deficit from SOME point, which would turn into a new maintenance weight.  We know for certain that certain maintenance weights in humans simply aren't healthy, even with adequate micronutrients.  Adiposity below a certain level and body weight below a certain level can be deadly.

 

4.  Soooo wouldn't #2 actually mean that people with certain maintenance weights must already be practicing CR, if unintentionally, simply because their intakes are much lower than their body-doubles?

 

5. Whether or not the purpose of CR is weight loss to a low maintenance weight, isn't this the inevitable result (if you actually are restricting)?  In this case, wouldn't it be best to study healthy low-weight people in general?  And shouldn't we see that people who have been very slim and healthy--not slim due to disease--all their lives live remarkably longer?  And IS that what we see, with the Okinawans?  Looking at deliberate CR versus behaviors that cause CR, there shouldn't be a difference--all that should matter is a lower caloric intake which would result in both a low maintenance weight and the various other side effects.

 

6.  Or perhaps the more extreme, short-term food shortage stresses that occurred during WWII for both Ikaria and Okinawa produced longer-term changes in the population?

 

7.  How does one track or measure the changes that successful CR would cause, anyhow?  Lower body temperature?  And what else is actually measurable that shows adaptations consistent with those in animal models?

 

I hope I'm not asking things people have asked 100x before.  I have checked the archives.

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GenGenimney, first, welcome! Second: These questions have indeed been asked before, but they haven't been answered satisfactorily, so it's definitely worth it to pose them anew.


 


Edit: We should start a new thread for your question 6 (the other questions are all focused on determining the right level of CR). See:


 


https://www.crsociety.org/topic/11243-short-term-food-shortages-and-crd-populations/


 


- Brian


 


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I'm glad I wasn't missing anything!

 

I can't remember numbers, but my triglycerides have been exceptionally low in the past, too.  I have a sleep disorder (non-24), and the only time it goes away is on CR/low body weight, so I'm trying to get back to that for those reasons, too.  It's quite annoying otherwise.  (I joke that I'm just on a slower rhythm than the rest of the world.  I got teeth slowly, I grew slowly, I finished puberty years after other people--who's still gaining height at age 21????, I entrain to a nonexistent 26-hour day, my cycles are longer than other people...  But at least the sleep cycle thing can be influenced by body weight.)

 

I suppose what I should do is measure everything CR-related and see if it goes into unusually low zones, and that would be a good indication....

 

I'll be at 40% restriction for about another month, then down to 30%.  We'll see what my body weight is doing a month after that.

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I don't have my baseline BP...but I checked it today, and I'm back down to 97/60.  High-ish but not scary-high, like it was before.  Resting heart rate is running a little high at 54 BPM, but I'm in quite a bit of pain today because I hurt myself yesterday, so I can't expect it to be 50-52, as it is now when I'm not hurting.  (I have chronic pain, and my BP and RHR variations reflect that.)

 

ETA:  I'm still pretty grotesquely over-fat, with 23% BF.  At 20% BF, I SHOULD start seeing truly normal results again for me.

 

For fun, I picked up some ketone urine strips.  I didn't know it was so easy to check for ketogenic states!!!  I really want to examine the assertions of people that 12/12, 16/8, or 18/6 unfed/fed can induce temporary ketogenesis.  Should be fun....

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  • 4 months later...

GenGenimney, first, welcome! Second: These questions have indeed been asked before, but they haven't been answered satisfactorily, so it's definitely worth it to pose them anew.

Hi Brian,

I found many of these questions quite interesting as a new CR member. I've been searching the threads trying to find answers to how to introduce the diet slowly and if the benefit can be achieved at different levels and how to know which level is best for each individual. Specifically, I've read that starting CR earlier means you need to reduce more dramatically than others (I'm 26) and also that those who are naturally thin may benefit from less CR (I fall into this category)

 

 

 

2.  The idea of a body-double makes much more sense

 

4.  Soooo wouldn't #2 actually mean that people with certain maintenance weights must already be practicing CR, if unintentionally, simply because their intakes are much lower than their body-doubles?

Hi GenGenimney,

 

Would you mind clarifying for me what a body-double is? I haven't heard or read about this yet in my past couple months of research.

 

In response to number 4- I have wondered if I've been unintentionally practicing CR a lot of my life and now, for the first time I'm trying to add in the ON onto the end :). We were poor when I was very small and then growing up I was very athletic and ethically vegan so I didn't get my period until I was almost 20 and now, at 26, many people still think I'm in high school or have just graduated. It's also quite impossible for me to eat my caloric requirements alotted by my FitBit without feeling abhorrently stuffed and semi-ill and gaining weight, so I just don't.

 

Thank you for your questions!

 

(PS- body fat 25% in a woman is, I believe still "normal" even if not optimal for you... try to be a little kinder to yourself <3)

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Hi Casey,

 

 I've read that starting CR earlier means you need to reduce more dramatically than others (I'm 26) and also that those who are naturally thin may benefit from less CR (I fall into this category)

 

As far as I know, there is no evidence for the former (i.e. starting CR young means more serious CR is required to have benefits). I think you may be mistaking the pretty well-supported idea that a greater degree of CR can be tolerated, at least in rodents and possibly in primates too, when started at a young age than when started later in adulthood, when the body isn't so resilient. As for benefits, if anything the evidence suggest that it is cumulative years of CR (at whatever degree of restriction works for you) that count towards total health/longevity benefits. In other words, starting younger will result in more benefit than starting later with the same degree of restriction. See this post for evidence suggesting that starting earlier appeared to be better for CR monkeys.

 

As for the latter (being naturally thin may make it harder to attain CR benefits) - this one may have some validity to it, if only because being naturally thin makes it harder to practice CR safely (i.e. while maintaining sufficient metabolic reserves that may be required if you become sick or injured). But the jury is still out on this one. Once latent disease and unhealthy causes of thinness (e.g. smoking) are factored out, it doesn't appear that thin people in the general population (i.e. BMI < 18.5) are at a disadvantage relative to 'normal' weight people when it comes to health and longevity. Here is an entire thread on the topic of the benefits (reduced or otherwise) of CR for naturally thin people.

 

--Dean

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