The aim of the following text is to present my view on the following
question: is instinct adapted to selected food?

The general theory is that a food is palatable as long as the benefits
outweigh the harm. Of course, the taste may be educated (phenomena of
neophobia and aversions), but there are two remarkable exceptions:
sugar ans salt. While I don't really understand the reason for
"natriophilia", our natural attraction to sugar is pretty
understandable: in ancient times, high-sugar fruits were scarce, and
the Paleolithic human needed a great deal more energy than modern,
sedentary humans who live in well-heated apartments and travel by
car. Maybe it is also the reason why we usually like fat (I have heard
that 0% fat cakes are quite tasteless).

The next question is: how could the so-perfect Nature let us have such
an abnormal attraction to sugar? More generally, ethology provides
numerous examples of ludicrous behaviors. Some birds are frightened by
a fly on the ceiling, because they believe it is a predator. Other
species can also use these kinds of aberrations for their own
advantage: some butterflies have coloured patterns on their wings that
look like eyes to frighten predators; cuckoos are fed by other birds
that believe they are their offsprings. Statistically speaking,
instinct works rather well, but in some instances it can be wrong. Of
course, a broad variety of instinctive -and stupid- behavior can be
found in birds, but much less in higher mammals. Nevertheless, humans
have kept more phylogenetic programs than we might think: for
instance, why do we find rabbits so "cute", "lovely"? The reason is
that the shape of the head, the comparatively big eyes, etc., make
them look like our own children. We certainly do not have the same
feelings when looking at young pigs or rats.

So, while during the Paleolithic the attraction for sugar worked
generally well, it seems that with modern fruits it can be very
deceptive. I still remember the time when I ate fruit salads, and I
added sugar when they were too acid: hence the cumulated effects
of an excess of energy and too much acidity. Also, think about
the corrosive drinks such as Coke that could never be ingested without
the sugar.

Thus, I think we should consider that modern fruit are as unnatural as
fruits with sugar added -when the taste becomes unpleasant, it is
already far too late (remember the amount of acid fruits we can eat
with only a small amount of sugar sprinkled on it).

Now, concerning selected vegetables, I don't see any risk of overeating,
since sugar is not involved. Modern vegetables are probably less bitter
because they contain less toxins, and thus are at the same time more
palatable and more beneficial: thus, the instinct probably works -with a
remarkable exception, modern wheat. In that case, the body fails to
detect the high amount of gluten, maybe because the very low quantity of
gluten that was ingested in ancient times didn't make enough selection
pressure.

So, how to avoid eating too much fruit? Practice is more difficult than
theory... Maybe eat vegetables first, since sugar becomes less attractive
once the energy needs are fulfilled. But fruits do not combine very
well with grains, nuts or RAF, and are often better absorbed as monomeals
(perhaps "monofruit"?). Not so easy to rely on intelligence rather than
on instinct...

Best wishes,

Jean-Louis