I am looking for a moist cat food that is high in calories that can be bought over the counter for a senior under weight cat. Any ideas?

Have you taken this cat to a vet to find out WHY it's under weight??? It could be kidney disease, cancer, worms, any number of things. Just feeding it more isn't going to solve the problem.

I'm also betting this cat isn't very old - just neglected. I have a TWENTY ONE year old cat who is still perfectly healthy.

Wellness canned cat food is good and has many varieties. You can get it at Petco or PetSmart.

https://www.youtube.com/watch?v=1PBjR1lefb8

My vet put my cat on EVO high protein canned food. It can be bought on Amazon, Chewy.com and at some pet supply stores. My older cat has several health problems and this has been great for him. It smells like people food...and my cat loves it.

Kitten food is generally higher in protein and fat, which can help get them through an illness. The higher protein might not be good for the kidneys in the long run, but you can do blood work every few months so that you can switch if it affects the kidneys. You could try adding salmon oil to your regular food. More fat and calories, very palatable, very little hassle. If possible, smaller, more frequent meals can help, too. Good luck with your older kitty!

I put ours on meat baby food for a while. The vets also carry KD food which is a canned food (around $2 a can) that you mix with a little water, it's very high in protein and can help the cat.

Buy Whiskas for cats.

Go to petsmart they have exactly what you are looking for