Why do calorie restricted mice live longer?

[Guest guest]

> Why do calorie restricted mice live longer?

[snip]

> 1. Lower body weight is causing the life extension.

>

> 2. Lower Body fat is causing the life extension.

>

> 3. Lower calories (independent of 1 and 2) are causing

> the life extension.

The research has pretty thoroughly established that it is #3 that leads to

actual extension of maximum lifespan (though the other two may improve

longevity within the normal lifespan).

ob/ob mice only CRed to levels of 'normal' weight and body fat, but still

calorically restricted, do show the CR effect of increased maximum lifespan.

Likewise, well-exercised mice or mice genetically bred to have a lower

weight and body fat do *not* show an extension of maximum lifespan.

Therefore, #3 is pretty clearly the active agent -- however, just why it

works is still open to some debate (less damage from free radicals, a

genetic 'starvation' response, increased efficiency in 'burning' the body,

slower cell-divisions, or a synergy of all these factors and others...).

> Why did the mice fed once a day live longer?

I haven't heard about this, so I can't comment. Perhaps the particular

study just happened to use once-a-day feeding to achieve dietary

restriction, while the control mice had ongoing free-access to food.

Cheers,

________________________

Gifford

3-5 Humanities Centre

Department of English

University of Alberta

www.ualberta.ca/~gifford