Hi Rob,
Let me make a small correction here as the above is not exactly
accurate, but does work in your situation. :-)
Basically, an indoor cat with an average activity level needs about 15
caloires per pound per day to maintain body weight. In order to drop
weight a reasonable cut in calories would be 30%.  For a cat that only
needs to lose a little weight, feeding them the calorie requirement they
would need to maintain their target weight probably wouldn't even amount
to a 30% drop, so it's reasonable to use that number as the calories to
feed and will cause a nice slow weight loss. However, for cats that need
to lose quite a bit of weight, feeding what they would need to maintain
the target weight may be too drastic a cut in calories.

With Tucker, who originally needed 315 calories to maintain his weight,
we cut his calories by 30% to a little over 200. Now that he's dropped
some weight we've made another slight cutback to continue the weight
loss, but keep it *slow.* If we had fed what he needed to maintain his
target weight, his calorie intake would have been cut by over half which
is unhealthy and could put him at risk for developing hepatic lipidosis.
I hope this clarifies things better.

Also, if your one cat is not advancing in this as well as the other
cats, don't worry about it and just make sure she's eating enough of
whatever you can convince her to eat, even if it means more of the old
food or whatever else she'll eat and less of the healthier stuff for
now. Some cats take a lot more time than others to adjust to change, and
she'll come around eventually.:-) I have cats that took many months to
adjust! So far it sounds like you're doing pretty good for such a short
time. :-)

Megan