cron-web.org

[A1CR]

[posted on behalf of CRON4healthyfuture; 2002-07-21]

Someone noted:

> After reading the article CRON4healthyfuture mentioned on anorexiants and CR:
>http://www.americanaging.org/past_meetings/AGE01/abs/Ukraintseva.htm
>I was wondering if the increased metabolism, evidenced by the increased
>temperature, seen in the rats on the anorectic program (which would not
have
>experienced hunger), is a good thing. I remember some time ago reading a
>post from Dean saying something to the effect against "grazing" which, I
>imagine, would have reduced hunger (as a Zone diet would), similar to the
>anorectic rats.

That's the most important question that needs to be answered presently, in
my opinion. All of this talk we like to engage in daily about the more
esoteric discoveries being made about the biochemical mechanism of caloric
restriction is nice, but how should it all translate into our daily
implementation of the plan?

Everyone agrees that fewer calories is obviously better. But is the
experience of hunger necessary? And how does meal frequency affect things?

I think the research base is still quite equivocal regarding the impact of
meal frequency on health and obesity. There are going to be so many
individualistic and idiosyncratic things going on in the various smaller
studies designed to investigate it that it becomes difficult to determine
what exactly is going on when one subjects all the studies to meta-
analysis.

And nobody knows if hunger is necessary. I strongly suspect that it is,
but I have little firm evidence to support that. I rely only on my
understanding of the evolution of nervous system complexity. The
hypothalamus, the brain structure most involved with all of your instrinsic
drives as well as your temperature regulation, is located in the Midbrain,
specifically in your Diencephalon. This structure is very old and very
evolutionarily preserved, which is understandable, because organisms that
figured out when was the best time to eat and conduct other activities
would have a significant advantage compared to organisms that had no
coordinated regulation of their intrinsic behavioral drives.

In other words, hunger (and subsequently, the hypothalamus) must have
evolved a VERY long time ago to tell an organism that, "Hey, you need to
stop looking for a mate and chow down." (That could explain a lot
concerning decreased libido.......)

I believe our conscious sensation of hunger is a very primitive function of
the hypothalamus as a regulator of nutrient intake, and thus DIRECTLY
correlated with the degree of nutrient deprivation the body must be
experiencing. It seems too important, too nested in our "intrinsic
programming", for the body to take a chance on have an INDIRECT correlation
between hunger and the actual degree of caloric deprivation the body is
experiencing.

Now, I think where the situation gets murky is the PERCEPTION of hunger.
We can all sense hunger (except, presumably, someone who has a hypothalamic
lesion). But what we do with that sensation is different. Everyone has
different thresholds where they will make the cognitive decision to cave
in, and that may have a lot to do with how we were raised and how
we "learned to eat", in addition to genetic factors.

Now things like yeast may not experience "hunger" per se, but they do
experience adaptive changes to nutrient restriction. My belief is that the
hypothalamus is basically functioning as a little "chemical dipstick" that
checks bloodstream nutrient levels, and, when it detects abberations in
nutrient availabilities that parallel those in "yeast hunger", it will
integrate that information and induce changes in neurotransmitter release
at critical hypothalamic regions, as well as induce the release of
hormones, to cause you to "feel hunger". Whether or not you decide to eat
is up to you, I guess if you are a "Zen Master" (Elixxir? just kidding...)
you can find ways of disregarding that signal. These changes in
neurotransmitter signalling and hormone release (the hypothalamus also
controls the pituitary, the so-called "master gland) could be responsible
for much of the caloric restriction effect in multicelluar organisms. If
you do something to modify that neurotransmitter release, and thus the
sensation of hunger, you may also be reducing the degree to which the whole
body is made aware of the current state of nutrient deprivation, and thus
you may be attenuating the "caloric restriction effect".

The yeast has no nervous system for it to "sense" hunger, but its nucleus
can figure out when things are going poorly from a caloric standpoint. The
nucleus, as well as its proteins, are functioning as its brain. Proteins
are said to be capable of more powerful processing than some of the most
sophisticated microelectronics available today, specifically because of
their amazing integrative abilities. One region of a protein can sense
glucoprivation, and that information is transmitted through a
conformational change to the active site, which can then affect the
function of subsquent proteins. The proteins of an individual cell can
almost instanteously figure out thousands upon thousands of different
biochemical variables instantaneously, and act immediately upon them. Talk
about parallel processing! They really are amazing, and some of the same
processing functions we attribute to "brains" can be paralleled by such
simple cellular entities.

Now, even while you are calorically restricted, the sensation of hunger
seems to wax and wane, right? Some people may interpet this to mean that
hunger is just a side effect of the whole process and not necessary for the
beneficial effects. I think a better interpretation is that a lot of the
neurotransmitter and endocrinological activity associated with hunger is
pulsatile. Researchers are coming to a higher order of understanding
regarding the critical temporal aspects of hormone release. They are
finding out the rhythm of hormone release can have as big an impact on the
observed effects as the dose, sometimes even more so. This is one reason
why growth hormone supplementation is still very controversial; just
dumping hormone in at physiologically arbitrary times could have a negative
impact. (Look at hormone replacement therapy, as well..........)

So my "gut" feeling, so to speak, is that you need to be a good bit hungry
to be experiencing CR effects. Not pica-esque ravenous, but hungry
nonetheless. It does not have to be constant, I don't even think the
body/mind would even bother to signal for hunger constantly. During
ketosis the body shuts down the hunger signalling almost completely as it
is interpeting the glucoprivation as starvation, for example, and it does
not want to cause such intense suffering in the organism so as to prevent
the successful acquisition of food.

Hunger comes in "pangs", and the best I can reason is that this is how
hunger basically works, in that, like leaving Post-It notes up on the wall,
it kind of, in first gentle terms, keeps reminding you that you should
probably eat. Eventually it gets more and more plaintive, and then it gets
downright coercive with you. But I think the process is very pulsatile and
in constant flux, and that is why many people state "They feel no hunger"
on the CR program despite reduced caloric intake in comparison to ad lib.
Additionally, there are additional influences on satiety that come from gut
activity that can premptively abrogate a lot of the sensation of hunger,
but I would keep in mind that these probably function just to prevent
pathological overeating as well as in a kind of a Pavlovian reward system
for listening to the hypothalamus, an example of "negative reinforcement",
where the noxious stimulus, hunger, is removed when you eat, giving you
something to remember the next time you experience hunger.

Long response, I know, but just some things I keep in mind when reading
about things.

All this talk about hunger is making that Satietrol look awfully nice.

But, as I state above, I am a little concerned what reducing the sensation
of hunger may have.