weight gain cat food

Question
Is there any dry cat food that's best to help my cat gain weight? She is 8 years old. Outside cat. Comes in at night. Worms have been ruled out, just need a weight gaining dry cat food. Thanks

Answer
It would be helpful to let me know what she eats now, how much she is eating and if she hunts. Has she also been given tapeworm medicine? (you can only buy that at a vets office, it is NOT an OTC drug). Does she eat lizards?

Lizards will bind with their B vitamins rendering them non-absorbable for the cat. They can starve to death eating lizards.

Has she been tested and vaccinated for Leukemia? These viruses will make a cat un-thrifty and they are ultimately fatal.

If all the above is good, my next question is how thin is she? Is she bony? Is she 8lbs, 10lbs?

Send me some more information and I can probably help you much more efficiently.