Re: Revisiting Phelan's mathematical model of calorie restriction

[Guest guest]

Hi Dave:

I contacted him at the time his piece was posted here, and asked him

how much difference he thought CR would make to rhesus monkeys, which

are, of course, quite closely ralted to humans. His answer was

something to the effect: 'marginal'.

At the time I knew, but did not mention, that Dr. Hansen had already

given a conference presentation which indicated that the preliminary

data coming out of rhesus monkeys studies suggested the monkeys put on

CR at the human-equivalant age of 50, looked to be living ~30% longer

than the fully fed control monkeys.

I always have had a personal preference for empirical evidence ; ^ )))

Rodney.

>

> Recall that, a couple years back, Phelan published a mathematical

model

> of caloric restriction, one of the results of which was that even

> serious caloric restriction in *humans* will extend lifespan by only

3

> to 7 percent. Is anyone aware of a subsequent scientific critique

of

> his mathematical model? Or does it stand largely unchallenged at

this

> point?

>

> Thanks,

> -Dave

>

[Guest guest]

Hi All, There is a response to human CR naysayers. The other shoe has dropped it appears, in the pdf-available below paper. There are other similar reports. Yu BP.Why calorie restriction would work for human longevity.Biogerontology. 2006 May 5; [Epub ahead of print]PMID: 16676136 http://tinyurl.com/qfrt9 ... In my view, a couple of reasons could be at the root of the controversy ( http://tinyurl.com/hbccm ; http://tinyurl.com/hzm3e ). The most obvious reason is that at present, there are no experimental human data that permits us conclude that CR extends maximum lifespan, because the CR paradigm has not been tested out under the same well-controlled conditions on human subjects as with rodent studies (Dirks and Leeuwenburgh 2006). The

next major reason is that too much emphasis has been placed on life extension for assessing CR's effects, while neglecting more important preventive actions against physiological declines and the suppression of life-shortening diseases. This unfortunate practice most likely came about from the work based on the mortality data of human and lower species, like fruit flies and nematodes, in which life extension, not functional assessments, was used to assess CR's efficacy (Phelan and Rose 2005). Analysis of CR's effect based on the life extension may be of interest, but it is a limited approach and not sufficient for assessing CR's efficacy on the functional aspects of human longevity. Thus, more accurate answers would come from assessments of CR's prevention against functional declines and its ability to suppress longevity-compromising disease processes.orb85750 <orb85750@...> wrote: Recall that, a couple years back, Phelan published a mathematical model of caloric restriction, one of the results of which was that even serious caloric restriction in *humans* will extend lifespan by only 3 to 7 percent. Is anyone aware of a subsequent scientific critique of his mathematical model? Or does it stand largely unchallenged at this point?Thanks, -Dave

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