Bring up Google and enter "Iams" as the search string. In any case,
below is the website:

http://www.iamsco.com

Read all about the formula there.

<snip>

John--

Our fat cat has eaten Iams hairball/weight loss for about four years.
We free fed and
she wolfed it and begged for more. On a suggestion from someone here,
I started giving
her canned food, just a little at a time, like a third of a 3-oz can
three times a day. In addition, she gets maybe a third cup of dry
food, just a sprinkle in the morning and at night. She has stopped
eating all of the dry food--it is as though she rations herself. And
she loves the wet food. AND she is losing weight. She clearly finds
the wet food more satisfying. The dry diet food is full of carbs and
apparently they just keep eating because they are not satisfied--like
you might do if you wanted steak but could only get to Popcorn. As for
the hairballs, get some Laxatone, or whatever your vet sells in a
tube. It usually tastes like molasses and they lick it right off your
fingers, or you can put a dab on their noses. Another
thing--apparently dry food if eaten fast can cause upchucking because
it expands in the stomach. Hope this helps.

IAMS has a hairball formula/weight loss dry food.  You should try that.

Sue