Setting CRON Objectives

[Guest guest]

Hi folks:

For some reason a comment in one of Warren 's posts here, long ago, has always stuck in my mind. It was a finding that, among the restricted mice, those that lived the absolute longest were the ones which, while fed the identical very restricted diet, somehow managed to maintain the greatest body fat, compared with the other restricted mice.

(If anyone can recall the paper which found this, please post it.)

There is a number of possible explanations for this. One I particularly like is that perhaps the longest-lived mice were those which managed to avoid any exercise over and above the threshold amount absolutely necessary for health, thereby storing the calories as fat that the others were burning in exercise ; ^ ))). Another possibility is that the longest-lived mice had a lower 'metabolic rate', or an especially low body temperature. Or they could have been the more diminutive mice, using up fewer calories while fed the same as the others.

In any event, whatever the explanation, if it is true, then focussing on body fat percentage as a measure of compliance with CRON, which is what I have been thinking is appropriate up until now, may be mistaken. Rather, perhaps the emphasis should be on attaining excellent typical CRON biomarkers** while MAINTAINING THE HIGHEST BODY FAT.

In this case, perhaps it may not be helpful to squeeze the last few decimals out of some of the biomarkers past the point of diminishing returns, by dropping caloric intake appreciably further to get a comparatively small additional improvement in biomarker values.

Instead, maybe it would be better for longevity (based on the Warren quote) to maintain a somewhat higher body fat, if the biomarkers are already very good? (I am expecting Tony to agree with this!)

Of course arguing against this is the fact that one study found 60% restriction produced longer lifespans than 40% restriction. The 60% restricted animals couldn't have had a lot of spare body fat! But perhaps the longest lived among them were also those with the highest traces of body fat?

Any thoughts? Even better, any papers that might help to clarify this issue?

** lipids, BP, CRP, glucose, insulin, T3 .......... perhaps using the WUSTL study subjects' data as a benchmark for 'excellent'.

Rodney.