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Re: Human Evolution and Obesity
Philip Deitiker (Pdeitik@bcm.tmc.edu)
10 Oct 1995 20:55:47 GMT
Debra Mckay <debra.mckay@utoronto.ca> wrote:
<snip>
>Not necessarily. If you want to talk genetics, modern humans are
>genetically attuned to a hunter/gatherer (gatherer/hunter?) diet because
>that's basically what we've been over 99% of the time since H. sapiens
>arose. Agriculture arose only 10,000 years ago, which simply is not >long enough for any significant change in the way our bodies =
deal with >diet to have evolved. There is a whole hatful of diseases that exist >simply because we are no longer eating what our bo=
dies can deal >with--and obesity is one of them. It's not "too much food" that is the >problem in the US--it is too much of the *wro=
ng* food. Poorly nourished >people are often overweight.
Wrong food or right food, is very dependent on lifestyle and enviroment.
If you want to consider obesity in societies in which food is more or
less continously avialable, then overwieght could be a detriment. If the
same food supply is available in a tropical/arid region in which
dissipation of body heat is important, then excess body weight is even
more detrimental. However body fat and caloric intake are not synonomous.
A thin active person could consume 2 or 3 times the amount as a fat
lethargic person (look at competitive cyclist). One problem with modern
society is that we have minimized the amount of labor intinsive tedious
labor which predominated prior to the industrial revolution, in addition
people often did not live long enough to develope the types of obesities
seen today, and finally to some degree body fat could have been extremely
important in surviving periods of scarce resourses (particularly long
winters seen in extreme northern latitudes). For these people body fat
acts as an energy reserve and insulator. It could be predicted that the
underlying genetic parameters are probably present in most populations
and like skin color, once the enviroment changed, there would have been
fairly rapid selection for those who had protective characteristics. Also
remember that it wasn't too long ago that european americans were face
with similar envirmomental challenges which could have favored large body
size. The problem with modern societies is that in few places is there
the same type of periodic enviromental challenges anymore. Living in the
a developed country means that almost all food types are available year
round, homes are heated to near tropical settings in winter and cooled in
summer. There are no real enviromental signals (except possibly the mass
media) which direct either a fit or fat lifestyle.
To give an example most modern people drink coffee in the morning as a
stimulant to arouse them. This could be considered a junk food except one
has to consider the prospect that most people don't want to go back to
the days in which the stimulant for getting at 5 AM was their or their
families survival depended on it. There are other ways to arouse oneself
(like vigorous morning exercise) but they do not fit well in the
temporally overloaded modern lifestyles.
Fatty foods and the like are really not required anymore by humans yet
we haven't lost our taste for these types of foods, the fact that the
fatty foods give pleasure suppors an arguemnt that ingestion of such
foods, whenever available, was a one time important for our survival. As
far as disease is concern many of these same diseases can result from a
lack of exercise, and most dietician now point out that it very difficult
to loose fat without exercise, semi-independent of diet. I not here to
defend 'junk food'. But junk food is not a new age addiction. The problem
is that our lifestyles have changed so subtly over the last 100 years
that considerations about modifying dietary intake and execise patterns
did not reach the public health agenda until about 10-20 years ago, when
obesity began to become a public health issue.
Philip
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