[While this is the first post of this article to MoreLife, both Paul and I have
received private forwardings of it. It has also been the subject of discussion
on the sci.life-extension newsgroup. **Kitty]

If interested, I could probably dig out the article
from "Science"(Think I deleted)
Bob


Fat Mass, Not Caloric Intake Linked to Longevity in Mice

NEW YORK (Reuters Health) Jan 23 - While caloric restriction has been
shown to increase lifespan, findings from a new animal study suggest
that it is fat mass rather than caloric intake per se that determines
longevity.

Because leanness and caloric intake are interrelated, it has been
difficult to determine the relative importance of each in enhancing
longevity, Dr. C. Ronald Kahn and colleagues, from Harvard Medical
School in Boston, point out in the January 24th issue of Science.

To address this point, the researchers created a strain of mice that
lack insulin receptors in their fat cells. This alteration causes the
animals to have reduced fat mass and protects them from age-related
obesity. However, their food intake remains normal.

The researchers found that the experimental mice had a mean lifespan
that was about 134 days longer than control littermates. This
represents an 18% increase in their usual lifespan.

In addition to sorting out the effects of leanness and caloric intake
on longevity, the findings also have therapeutic implications. "Perhaps
one day if we are able to find a drug to reduce or block insulin action in
fat cells in humans, we might be able to prevent obesity, as well as
type 2 diabetes and other metabolic diseases," Dr. Kahn said in a
statement. "And who knows, they might also live longer."
________________________________________________

[Here are the comments that I just sent to a friend.

The problem with all these highly sought alternatives to calorie restriction is
that calorie restriction is extremely well proven in many animal species,
whereas most alternatives have only one or two experiments to back them. They
are good in theory and many of their explanations may be partially correct for
the benefits of CR, but they are not likely to be a complete mimic. The
experiment you report has been found lacking as "proof" (that the CR effect is
merely equivalent to being lean or lowering insulin) for at least two reasons:
1) There are genetically fat mice which have their lives extended by CR just as
much as do lean mice.
2) The amount of life extension in the reported study was not as much as in many
CR experiments with the same type of mice.

Furthermore, it has been known for years that CR greatly lowers total life-time
insulin and there have been strong theoretical reasons why a diet and regimen
which keeps insulin low should be life extending. Moreover, there are several
supplements which will promote this effect (chromium, vanadium, HCA
(hydroxycitric acid from Garcinia Cambogia), RLA, etc). Metformin is a very
safe drug which accomplishes this and inhibits glycation as well.

BTW, when last tested both my (and Kitty's) fasting insulin and glycated
hemoglobin were quite low :-)

Finaly, it seems an awful waste of food to eat it and then have it not be used
by the body, but simply excreted. This reminds me of the gluttony among wealthy
ancient Romans who reportedly forced themselves to vomit so that they could eat
more delicious food.

Still, I too think that for most people becoming lean by restricting calories is
a very important aspect of the process. That is why I put so much emphasis on
reaching and maintaining a BMI under 20.

Added later:

For additional discussion see the ongoing thread on sci.life-extension:
http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&th=9ebf0bdea4bad779

There is a suggestion in the discussion that the extra calories were
metabolized. If this is so, then it is hard to understand how the higher ROS
(reactive oxygen species) load would be life extending, especially for mice
which generally die of cancer. This is another reason why this study may have
little application to humans. However, the sle thread also points out that fat
cells have major endocrine secretions which can have highly negative effects.
--Paul]