My experience;  and a comment!  In response to tests that
show eating sugars improves brain function!

In 1950,  working six ten hour days on a Construction
project,  with the fear of getting fired if I slowed down,
unloading 92 lb cement bags, carrying lumber, digging
foundations,  carrying material up ladders,  and making more
money than I could get at any other job that I was aware of;
I GOT TERRIBLY TIRED IN THE AFTERNOON!

I was getting enough sleep,  so I went to the Library and
searched for a different cause;  it seemed that it must be
food.   I found Gaylord Hauser's book;  "Live Longer,  Look
Younger".      Someplace in that book he wrote something
like: "If you eat sugar and white flour,  you will get tired
when you have used them up!    He recommended a diet of
fruits and vegetables and meat and fish and nuts  and
brewers yeast and wheat germ and whole grains.

I chose to follow his advice.   The brewers yeast takes some
getting used to!   I began eating close to Paleo,  lots of
rare steak and eggs and salads and veggies  and fruits and
nuts.  And real whole grain bread.

There was no immediate remedy,  I did not suddenly feel
better,  I got stomach gas pain from the sudden change;  but
I kept at it.   It did not seem to help after a month or two
but I kept at it until it was a habit.  Then one hot
afternoon a year later I was working diligently and realized
that I was no longer tired.     I had  gained strength and
energy.   Lots of energy.    Now FIFTY YEARS later I still
have lots of energy.  (Now I take vitamins  also.)

There was a feature on Public TV some years ago by Covert
Bailey,  a  sports trainer.  I  seem to recall that he said;
Marathon Runners who burn their own body fat,  finish the
Marathon;  then they run home instead of taking a Taxi.
However those Runners who depend on consumed carbohydrates
are all done after ten miles.    Then He said something
about like this;  "It takes a year for the intestines to
convert from burning sugars to burning fats!"    I found one
of his books but this statement was not in it.

Conclusion:    NONE of the usual "Research"  applies to
Paleo eaters as the usual subjects they test are eating the
SAD diet of simple starches and sugars with an occasional
bit of  meat  cooked well done.   When  the "Cholesterol"
SCARE  began  I did not believe the parts about meat and
eggs as I assumed all tests had been done on SAD eaters.
Now there is increasing reluctance to stay with the original
high carb low fat diet by at least a few health
prognosticators.

My case against the present day research is:   It is
useless;   as too many important variables are routinely
ignored.

Regards,   Lorenzo