Whats known is that quite early they do lose a significant amount of
their sense of smell, and thus their ability to taste food. Its so
common, researchers are actually working on diagnostic tests for AD
that involve testing the person's sense of smell. Here is an article on
the proposed test
http://www.medicalnewstoday.com/medicalnews.php?newsid=17776

Dramatic weight loss is usually associated with damage to the sense of
smell or taste, no matter what the cause of the loss of ability to
smell (also called anosmia)
Here is a good article on anosmia and what it means for appetite
http://hubel.sfasu.edu/courseinfo/SL99/anosmia.htmll

And yes, I do strongly believe that ultimately they lose their
understanding of the sensation of hunger. They may still feel it, but
it doesn't appear to trigger a connection with the action  of eating. I
expect its similar to what goes on with elimination or urination later
in the illness. They probably feel the physical sensations but have no
clue what they mean or what to do about them.

Mary G.

Sarah,  What you see depends on where the damage is affecting the brain.
 While loss of appetite/interest in eating is classic-for my MIL she is
literally unable to recognize what to do with her food (or most any
other object for that matter).  She doesn't know what a glass handed to
her is for and verbal directions are often not understood at all.  We
and the staff at her ALF have learned ways to handle her behaviors-but
sometimes we have to pen her in (to keep her from "going home to her
mother") with chairs (aides are sitting in them feeding others) and
sometimes actually feed her.  Some days are better than others-usually
once she is started she will go into "automatic" mode and finish on her
own.  She pretty much won't eat except at the dining room table, because
she doesn't trust her interpretations.  So we've long ago stopped taking
in cookies and candy.

Early on she lost recognition of familiar people and she cannot
understand photographs now.  Yesterday, she refused a piece of her
birthday cake (87!) but was intrigued by the purple icing.  The activity
director fed her 1 mouthful and Marion finished it up herself with no
problem.  But she is unable to recognize food as something to eat.
She'd just as soon carry it around in her purse,if they let her.  For
most things- we try to get her "into automatic".  That's most successful
for things like brushing teeth, pulling up underwear after toileting,
etc.  She pretty much is unable to think of these things herself, but
often will function without thinking.

Anyway, I just wanted to point out that this whole area is multi-faceted.

Beth