CR and energy used/body composition

[Guest guest]

Hi All,

This interested me.

" rats under CR expended 30 and 50% more energy, respectively, than

the prediction from their altered body composition "

The pdf is unfortunately not available for the below.

Energy expenditure of calorically restricted rats is higher than

predicted from their altered body composition

Mechanisms of Ageing and Development, In Press, Corrected Proof,

Available online 16

March 2005,

Colin Selman, Tracey , L. Staib, Jackie S. Duncan,

Christiaan Leeuwenburgh and R. Speakman

Abstract

Debate exists over the impact of caloric restriction (CR) on the

level of energy

expenditure. At the whole animal level, CR decreases metabolic rates

but in parallel body mass also declines. The question arises whether

the reduction in metabolism is greater, smaller or not different from

the expectation based on body mass change alone. Answers to this

question depend on how metabolic rate is normalized and it has

recently been suggested that this issue can only be resolved through

detailed morphological investigation. Added to this issue is the

problem of how appropriate the resting energy expenditure is to

characterize metabolic events relating to aging phenomena. We

measured the daily energy demands of young and old rats under ad

libitum (AD) food intake or 40% CR, using the doubly labeled water

(DLW) method and made detailed morphological examination of

individuals, including 21 different body components. Whole body

energy demands of CR rats were lower than AD rats, but the extent of

this difference was much less than expected

from the degree of caloric restriction, consistent with other studies

using the DLW method on CR animals. Using multiple regression and

multivariate data reduction methods we built two empirical

predictive models of the association between daily energy demands and

body composition using the ad lib animals. We then predicted the

expected energy expenditures of the CR animals based on their altered

morphology and compared these predictions to the observed daily

energy demands. Independent of how we constructed the prediction,

young and old rats under CR expended 30 and 50% more energy,

respectively, than the prediction from their altered body

composition. This effect is consistent with recent intra-specific

observations of positive associations between energy metabolism and

lifespan and theoretical ideas about mechanisms underpinning the

relationship between oxygen consumption and reactive oxygen species

production in mitochondria.

Al Pater