What do I feed my 17yr.old cat who has now showing signs of body mass loss?

Question
I have a 17yr. old male cat. I used to feed him Innova but my vet recently told me that it was boutique food & that store bought cat food is okay. Well, I did listen and I bought Iams Healthy Naturals. He's been on this for awhile. In December I noticed in just that week that he quickly loss body mass from his back area.
He was a big cat & has now slimmed down. I can't bring him to the vet because he has HIGH anxiety issues and no vet can touch him. All due to a past experience. The vet knows about this.
I am now feeding him MediCal Mature can food & dry. I don't even know if he has a kidney issue either. His habit of drinking water hasn't changed only that he tends to eat alot more.
What do I feed my little friend now? Do I still feed him the MediCal Mature food or is there something else better for him?
I Thank you for any advice,
Ellie

Answer
Hi:  The Innova Cat food is Great food!  I don't agree with the vet at all.  The Royal Canine Medi Cal is NOT so great...
HOW about mixing the Innova and the Medi-Cal food ( a 50:50 Mix)???
Also, give this boy some 2% cottage cheese - just 2 Teaspoons per day, for a few weeks.

Good luck !

Marie Peppers LPN MA