Why does calorie restriction reduce the rate of aging?

Robert Bradbury bradbury at sftwks.UUCP
Tue Aug 25 04:32:19 EST 1992


In article <willdye.714704220 at helios> willdye at helios.unl.edu (Will Dye) writes:
>
>Just so, we can say the peacock has an evolutionary advantage for all 
>those plumes (to get sex), but the falcon needs precise engineering 
>on each feather (to get food).  I'm NOT saying it isn't true, but it 
>just seems too convenient to grab any of umpteen different 'advantages' 
>to explain whatever it is we just saw.  If caloric EXCESS led to longer 
>lifespans, would we not say this is because of evolutionary advantage? 
>Lots of food means a successful critter, so they live longer and mate 
>more to make more successful critters in that environment.  Yeah, 
>yeah, you can think of a reason why that might not work.  But you can 
>also think of a reason why the opposite might not work (try!).  
>That's my point.  It just seems sloppy.  

I'm not using the evolutionary advantage theory to explain the specific
characteristics of a single species.  I am using it to explain a generally
observed characteristic in a variety of species and as an explanation for
why processes which might be viewed as harmful to the longevity of an
organism would not be removed by natural selection.

When one discusses aging one has to start with some facts (animals fed less
live longer than those fed more), propose a theory which is consistent
with natural selection (one would want to survive times when food is
scarce and most animals in the wild do not live to reach "old age") and
then look for biochemical explanations which connect the two.  I would
do the same thing *if* caloric excess led to longer lifespan but it
doesn't.  Animals who have lots of food on an ongoing basis would evolve
not a longer lifespan but faster growth and increased reproductive capacity
because that is what would increase the genes of those individuals in
the gene pool.  In fact natural selection works against this because
species which over-reproduce exhaust their food resources leading to
population crashes and possible extinction.

>
>Moving on...  I know this is an FAQ, but what is a good source for 
>non-technical info on the calorie-restricted diet?  I'm 6'3" and 
>have a strong set-point of 225, but I'd like to try one of those 
>CR diets or anti-oxidizing vitamin regimins, if it doesn't require 
>eating tofu and yogurt the rest of my life.  
>

The best source for calorie restriction is "The 120 Year Diet" by
RL Walford, Simon & Schuster, NY 1986.  There are some arguments that
restricting protein intake (i.e. less tofu and yogurt) may provide some
of the benefit of CR, see "Dr. Mollen's Anti-Aging Diet" by Dr. Art Mollen,
Penguin Books, NY, 1992.

The jury still seems to be out on whether altering your set point by
restricting calories for a period of time results in extended life.
If my hypothesis regarding B-oxidation/protein recycling is correct
then you lose the benefits of CR as soon as you have built up sufficient
fat reserves to resume the normal metabolism of fatty acids.  There may be
a routine, e.g. 2 months of CR to lose 10% of your body weight (fat)
followed by 2 days of pseudo-fasting every 3 weeks which will give
you the same results as 30-40% restriction of caloric intake but
we don't know that yet.

The anti-oxidant vitamin regimens will probably work entirely apart
from caloric restriction because the mechanisms are different. For
example, is pretty clear at this point that Vit. E is going to reduce
the oxidation of lipoproteins that will be absorbed by macrophages
leading to plaque deposition and heart disease.  There are a variety of
other benefits for E, C, Beta-carotene, carnitine, Q10, selenium and zinc
which would require an extended discussion but to date the best information
seems to indicate that these only gain you 5-10% vs. 20-40% for CR.  It
is worth noting that reducing the intake of iron and copper may be as
important as taking extra antioxidants because Fe and Cu play a key role
in the formation of hydroxyl radicals which damage DNA and proteins.
Of course determining the proper intake is very hard.  Too much Fe or Cu
probably increases DNA damage.  Too little Fe results in anemia, too
little Cu and you have non-functional metal containing enzymes such as
CuZn superoxide dismutase which is required to remove superoxide radicals.

-- 
Robert Bradbury			uunet!sftwks!bradbury

Death is an imposition on the human race, and no longer acceptable
				Alan Harrington, The Immortalist (1969)




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