> Jennie Brand Miller <[log in to unmask]> wrote
>
>
> I would like to know what people think of the idea that a tendency to gain
> extra body fat may be a survival stategy to cope with cold temperatures,
> rather than periodic starvation.

It seems to me there is a possibility that the extra body mass, far
from protecting the body against cold, will in fact cool it down, for
two reasons.

First the extra fat will act as a heat sink, absorbing heat produced
by the body.  This is familiar to fat people because their layers of
fat are not warm but cold, once equilibrium with a cold environment
has been established.

The supply of heat to the extra fatty tissue will reduce heat
available for the rest of the body, and therefore produce a lower
temperature in the body as a whole.

Second, the envelope of the body grows in area with more mass (albeit
proportional to the sqare root of the mass ) and so more heat is lost
to the environment.

These points both of course assume constant heat output by metabolism
and constant distribution by heart action.  It is possible that fat
people can metabolise faster, though I would have thought the reverse
was true, otherwise they would not be fat in the first place.

It is also possible that exercise given to the heart by carrying the
extra body mass around (like running with a back pack on, except it is
a stomach one) will develop its muscular power and thus increase its
output.

Whales and other mammals carrying fat as a sepcies may be adapted to
some benefits; however this would not seem to argue for specific
advantages for the fatter individual members of a species.


Dick Bird
School of Behavioural and Environmental Sciences
University of Northumbria
Newcastle upon Tyne
NE1 8ST