Metabolic rate and CR- time to say goodbye to the rate of living theory?

[Guest guest]

One of the most persistent notions commonly associated with reduced

uptake of nutritive calories to extend lifespan in several species is

that this effect is achieved through a lowering of metabolic rate.

Can anyone produce evidence to substantiate this? or point to CR

studies that actually focus on metabolic rate/flux or that this idea

is supported by more than unproven hypothesis or mere metaphoric

appeal? Evidence is steadily emerging that the opposite might apply,

that the increase in mitochondrial metabolism «might cause a positive

response to increased formation of ROS and other stressors, leading

to secondary increase in stress defence (mitohormesis), cumulating in

reduced net stress levels and possibly extended life span» (Ristow,

2007).

in one review one is told that:

These studies show that DR life extension is not caused by a reduced

metabolic rate, consistent with results in other species.

http://www.ncbi.nlm.nih.gov/pubmed/17063035?

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in another:

Two possible mechanisms by which DR increases lifespan are reduction

of metabolic rate and reduction of insulin/IGF-1 signalling.

Experimental tests have not supported either possibility.

http://www.ncbi.nlm.nih.gov/pubmed/15896824?

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There is evidence that DR causes increased resistance against

environmental stressors but no decrease of metabolic rate.

http://www.ncbi.nlm.nih.gov/pubmed/16782293?

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The increased life span caused by certain mutations in the nematode

Caenorhabditis elegans has been interpreted in terms of two metabolic

theories of ageing: the oxidative damage theory and the rate of

living theory. New findings support the former, but not the latter

interpretation.

or:

There is no reduction in metabolic rate or in the rate of generation

of superoxide and hydrogen peroxide from isolated mitochondria in

response to DR. DR acts acutely and rapidly (within 48 h) to reduce

the mortality of flies that are fully fed to the level found in

animals exposed to DR throughout life.

http://www.ncbi.nlm.nih.gov/pubmed/15935441?

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Dietary-restriction had no effect on mass-specific resting metabolic

rate both when measured as oxygen consumption... individual variation

in lifespan in wild-type flies, and life extension by dietary-

restriction and reduced insulin/IGF-1 signalling is not attributable

to differences in metabolic rate.

http://www.ncbi.nlm.nih.gov/pubmed/15288688?

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The above is culled from very recent findings. it seems however that

evidence was offered way back in 1985 but apparently had not caught

much attention...

The long held belief that reducing food intake lowers the metabolic

rate per unit of metabolic mass may be true in short-term dietary

programs but appears not to be true when a significant portion of the

life span is involved.

http://www.ncbi.nlm.nih.gov/pubmed/3157325?

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