LTS3 gave you some good resource sites. I found the fancy feast in the first one at least.
Here are tips on how to help your cat lose weight safely: http://catinfo.org/?link=felineobesity There are sot of "case stdies" of obese cats just like yours who got the extra weigth off. It took several months to achieve butit can be done.
For calorie content of canned foods, see http://catinfo.org/docs/FoodChartPublic9-22-12.pdf and http://www.petobesityprevention.org/wp-content/uploads/2010/05/Cat_Canned_Pouch_Foods.pdf
The Fancy Feast Classics are mostly under 100 calories. You would need a lot of those tiny 3 oz cans for your overweight cat a day. 3 oz cans add up in cost over time. A brand that comes in a large can size would be better. You don't need anything expensive. Friskies is an acceptable choice and there is a variety or two that comes in a huge 12 oz can size. The general recommendation is to feed 20 to 25 calories per pound of ideal body weight per day but for such an obese cat, you may need to feed more calories per pound for now to prevent fatty liver disease. You would need to first figure out how many calories your cat is currently eating every day. Then aim for a small reducation of calories for the next week or so. When your cat is ok with that, reduce the calories a little more. Repeat until the extra weight comes off. I wouldn't do more than a 100 claorie reducation at a time.
Oooh, those cats!She's been cheating on her diet so I'm sure she can be losing fasther than she is haha. Thank you so much everyone for your help and advice. Finally getting my girl back to healthy [emoji]128568[/emoji]