Steve Solomon writes about;  the effects of nutrition on
health as described in Weston Price's book  "Nutrition and
Physical Degeneration"  and others  at:

http://www.soilandhealth.org/02healthlibrary/0203longevityca
t/020305ppnf/PPNF.HTML

Here is a section on cats-

  " But Pottenger's business did well anyway, and his need
for cats grew and grew. Eventually he was housing so many
that he build a new pen to hold the most recent lot of them,
and to feed this batch, being overworked, he did not bother
to cook their meat, but just fed it raw as it came from the
slaughterhouse. Amazingly this batch of cats, even without
adrenals, thrived and were very healthy. Francis Pottenger
noticed this remarkable occurrence and decided to do a small
cat nutrition study. He divided up his cats into four groups
to observe the result of feeding the entire matrix of
possibilities: raw meat/raw milk; raw meat/pasturized milk;
cooked meat/raw milk; cooked meat/pasturized milk.
   Not surprisingly, he found that the cats fed on cooked
meat but who got raw milk did a little better than those on
all cooked food. The ones on raw meat and pasturized milk
did pretty well; the ones on all raw food did great.
Pottenger concluded that cats have a digestive system that
is not really capable of assimilating nutrition from cooked
protein foods. He concluded that the cat illnesses he had
been fighting were caused by mal-nutrition.
   Dr. Pottenger also noticed that cats on raw food lived
very long, often 20 years. They also had good temperments
and bred very successfully. When a cat that had been on raw
food was placed on cooked food, its life was greatly
shortened. The progeny of these cats began to change their
appearance. Their overall size lessened, their teeth got
poor, their reproductive organs did not develop well, they
had smaller litters, and within three generations on all
cooked food, they would barely reproduce, the females often
refused to nurse or mother their young if they did get
pregnant, and cooked-food cats developed nasty temperments.
   The one study Pottenger reported that had the most
profound effect on my awareness was when he took some cats
that he had intentionally degenerated by feeding all cooked
food for three generations. This group worsened to the point
that they would barely reproduce. Pottender then took some
of their young and began to feed them the ideal all-raw
diet. After four generations of perfect feeding, only some
of them began to look like fully-healthy cats. Degeneration
is much easier to create than it is to recreate perfect
health from degenerated stock. If these phenomena are
expanded to include humans, then we could guess that after
creating mass degeneration from mass mal-nutrition since the
turn of the twentieth century, it will take humans several
generations of near-perfect feeding to begin to virtually
overcome the effects.This also suggests to me the reason why
someone who has already developed a degenerative condition
often can't cure it simply by adopting dietary reforms.