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Calorie Restriction 
Other theories

Other theories

Firstly, the main theory about why CR works is the idea that it represents an adaptive response to low energy conditions, that prioritises maintenance activities at the expense of reproductive ones.

There are a few other theories that attempt to explain why eating fewer calories might lead to improved health and greater longevity:

  • Damage theories

    Damage theories suggests that damage to tissues (mainly by toxic agents) is responsible for much of the aging process.

    • Toxic calories

      This holds that caloric foods are either toxic - or produce toxins when burned.

      Those on calorie restriction consume fewer calories - and thus have fewer toxic byproducts to deal with.

      The toxic byproducts can be free radicals, glucose - or practically anything that can cause damage in the body.

      This theory may have some truth to it.

    • Rate of Living Theory

      This suggests that CR decreases the effective metabolic rate of organisms - which in turn reduces the rate at which they age.

      This theory is not supported very well by evidence - mainly since it is difficult to make much of a case for CR'd organisms having a lowered metabolic rate.

    In disucssion of "damage" theories, the "Micro Structure Exposure Theory" is often mentioned. This points out that the intensity of toxin the damage depends on the size and composition of the body - e.g. on how many vulnerable structures there are.

    While CR practitioners consume fewer toxins, they also have fewer tissues in a number of areas. Consequently, food- borne toxins might perhaps be expected to be more concentrated in the tissues CR folk can tend to lose (e.g. fat tissue) - and less concentrated in those tissues most preserved (e.g. brain tissue).

  • Resource allocation theories

    • Resource composition

      It may be that a nutrient spectrum low on energy - but high on other nutrients - "naturally" favours maintenance activities - simply because that is the sort of nutrient profile that maintenance activities require.

      This is a weak theory. It is unsupported by any evidence that I know of - and passes the explanatory "buck".

      However it is not impossible, and hasn't really been refuted - and it might yet explain some aspects of CR.

Tim Tyler | Contact