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Mechanism,  in  the 2015 topic "Do 'Naturally Thin' People Benefit Less from CR [etc.]?",  Dean P. provides another "case study"  (the more complicated formula involved was suggested by Shwet Shyamal--see thread for details):



Dean P. :  .... I'm not sure how actionable your formula is however. Take my case for example. Upon graduation from high school I weighed 128 lbs (BMI = 19.2). The follow year I gained 40 lbs of mostly muscle via weight lifting and swim team in college, so my BMI went to 25.2. I was healthy at both weights so which would you consider my "healthy early adult BMI", since it determines B, which in turn determines my optimal BMI to target, B'.


In the first case (healthy early adult BMI = 19.2), using 0.8 as the weighting factor as you suggest, according to your equation:


Let your healthy early adult BMI = B

=> Individual optimal BMI, B' = L^x * B^(1-x), where 0 < x < 1 depends upon what CR%, c you consider safe for humans on average               ... (1)


my optimal BMI would be:


B' = 17.5^0.8 * 19.2^(0.2) = 17.8  (= 119 lbs at my height  of 5' 8.5") 


In the second case (healthy early adult BMI = 25.2), according to your equation my optimal BMI would be:


B' = 17.5^0.8 * 25.2^(0.2) = 18.8 (= 126 lbs at my height)


My current weight (117lbs) is a bit below the first alternative, and substantially below the second. It's hard for me to see a sound basis for adjudicating between them.





It seems to me more reasonable to take Dean's weight prior to the 40lb gain as his "biological setpoint" weight.


Some guesswork seems unavoidable, and on top of that the 15% reduction from setpoint weight is, in M.R.'s definition of CR,  only a bare minimum , not a fixed optimal target.  In any case, a large number of other considerations and calculations would come into play during the course of CR practice   after the original deterimination of  one's theorectical "setpoint", arguably making the whole adventure as much  art as science.

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Hi Mechanism!


It's clear that you have a large RMR -- that is an inefficient metabolism; so you can eat a lot of food without gaining much weight.  In other words, you are "naturally skinny", like several of the best known members of the CR Society, such as Dean and Michael.


I'm the opposite -- I have a low RMR -- that is, an efficient metabolism.  A little extra food is rapidly translated into weight gain.


As Michael points out, BMI is not a good measure of degree of calorie restriction (if there is any good measure of that).


IMO, the best procedure is to reduce your calorie intake as much as you can, while maintaining adequate nutrition -- and keeping protein intake on the low side.  As time goes on, you may be able to tolerate further lowering of your caloric intake.



Being "naturally thin", severe calorie reduction does look difficult in your case -- not that it will mean that you're consuming too little food -- but that it might give you an anorexic look, even though you would possibly still eating more than enough food.


(It's a problem that I don't have.)


It would be interesting to see some studies on the effects of CR on genetically engineered rodents -- one genetically identical group with a high RMR, and other with a low RMR -- is there any difference in their response to CR?   


I don't know -- but my guess is "No".


  --  Saul

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That's one issue which discourages me in taking up a proper CR regimen. As soon as I cut the calories (especially the carbs), my weight drops, almost instantaneously. Past personal and dangerous experiments in starvation, which resulted in illness, have left me reluctant to allow a more than 5% bodyweight fluctuation from my ideal weight. 


Another fundamental issue, which MR did not address: is a calorie always a calorie? From the other thread on nuts and Atwater factors, it turns out it may be not. I have also my personal suspect that an abundance of fibers takes down the Atwater coefficients. Even though the modified USDA method is applied and other errors may supersede the factors errors.


Bottom line is that a calorie maybe a calorie, but there is some uncertainty in it, often unkown.


Nuts and fibery foods may yield less calories than the theoretical value from cronometer.

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By the way, and I don't know if at this point a new thread on the atwater factors should be initiated, but I just verified that the NCCDB database in cronometer, food=walnuts, uses the traditional factors: 9,4,3.75. Whereas the USDA voice on food=black walnut yields a slightly lower calories value than using the traditional factors

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To be correct, according to MR's guidelines which I just reviewed, absolute calories are not important, whereas relative calories are of interest, that is, it is enough to use a consistent database with a consistent method, since the reference is the weight, not the dietary energy itself.




Michael Rae:
If you are lucky enough to have had a clear, healthy 'setpoint' in your youth — a weight to which you tended to gravitate when you were in your early twenties, and that was within the healthy BMI range — take that as your baseline, and restrict Calories down to a level that keeps you at least 15% below that.


In my case, I remember that, in my early twenties, barring the periods where I ate too little or too much, my reference weight was about the same as now (56 years) = about 66 kg, with similar muscle mass and body composition.


Now, 66-15% means that, to be in CR, I should weigh no more than  56 kg. At least 10 kg less than now, preferably even less.


I'm not sure I'd feel good with that weight. Is it just mental reluctance and bias? 

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