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what's the threshold for human CR?

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What's the threshold for human CR?

For animals CR's def'd wrt adlib cals but that's a noisy approx to a ref intake for its genes. We shouldn't view gene twins as at diff CR lvl if 1 ate more b4. CR thresh should be a function of tot Cals (& maybe hght) or weight or BMI achieved.

Where should the line be?
On Cals, BMI, or other func?

Should a big % of BMI< 22/22.5 be considered in (at least mild) CR?

2500 Cal/d for men (2000 women) cited as norm. Not sure origin but quoted in papers, eg https://"For the average male to maintain his body weight, he should eat 2500 calories per day" So could take anything below this as CR. Eg male 2000 = 20%CR.

CALERIE study 2467cal baseline tx group achieved ~2175 2yr avg & was called ~12%CR. It was 1987 ie 20%CR 1st 6mo then 2233 ie 9% for 1.5y. Tx grp achieved BMI 22.3 @ 12mo, 22.6 @ 2yr so 9%CR stabilized at BMI ~22.5. But cohort 70% female so these numbers diff v above 2500/2000 ref.

1900s Okinawans estimated to eat 1785 cal. BMI 21. Biosphere 2 male BMI 24.6 -> 20.4 female 21.4 -> 19.0 Some papers say 1750-2100 cal. Others 2200. My notes of Fontana's papers on CRSociety members say 1800 cal 15yrs BMI 24.5 -> 19.5

What other cohorts are relevant?

Should human CR threshold be based on calories or BMI or other?
Where do you think the line should be?

(Clinically drs can test other markers of course, but I'm talking here primarily about an easy to judge test.)

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IMHO, based on own observations and on a lot of reading from different angles.

Brain regulates the constant body weight in +-3-5% surrounding "adlib". When there are extra calories they are distributed into reproduction, "less prioritized maintenance" and metabolism speedup (a measurable proxy - 24h heart rate). When there are even more calories they will be converted and stored, in the young age this will spawn more adipocites (up to some limits that are "multigenerational adaptive") that later will not disappear and stay ready for storing the new extras in the future.

When we are "bladerunning the negative edge" of this diapason the prioritization will switch off all possible, also speeding down the metabolism which is the easiest indicator to see (no need to see pre-anemic cbc and so on) - it moves in the similar +-5% area. In the longterm staying on this edge will slowly (with jumps) decrease the body weight (e.g. sudden infections requires to increase the core body temp, stealing several kilocalories in a few days, and so on, not mentioning bigger irregular spending).

The things above are valid for relatively active person, replicating hunter-gatherers daily activity pattern.

The absolute values are not only dependent on daily activities, the body frame is the key to understand the discrepancies in tens of different sources. 1700 for Oki and other documented natural low calories cases is possible for only 140-160cm high populations, those 170+ will not be able to run on this without weight loss even with very low activity and unhealthy lifestyle.

Thus if not targeting "net CR" using blood cbc, rhr and other things that are known for confirmation of being in CR (a dozen of them) but trying own chances for absolute values (trying to reach the limits of our species body design and ignoring the risks raised with this approach) then I would say it is better to look on Thomas Samaras' works on height and longevity to choose the data that will be representative for own body frame and then select the absolute calories target based on comparison. Heart rate observations in this case is also a good and cheap tool to tune more precisely.




Edited by IgorF
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As an Asian, I can have super-low BMI and 10-15% body fat, and the number of calories I eat in a day does not influene this. My weight is practically invariant to number of calories I eat, and I know a number of other super-skinny Asians who are the same. This still does not prevent excess calories from being detrimental in other ways (in CR mice, the best-performing phenotypes are the ones that *keep on weight*)

It's only true CR if you see reductions in WBC count, reductions in body temperature, and (possibly) reductions in free T3/T4.



Edited by InquilineKea
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