I can't add any more advice than what Sugarcatmom has but would like to tell you about my senior, Puddles.
Puddles is going on 14 years old and a couple of years ago she too was loosing weight, especially muscle mass and her fur was thinning and getting greasy. With the help of Sugarcatmom and Growler, I changed her food from kibble to Wellness grain free, then onto raw and Nature's Variety Instinct. She now looks like she did when she was 2 years old, the vets can't believe it. I also get a urinalysis and full blood panel done on her annually just to keep an eye on things as cats hide their illnesses very well.
Cat maid to:
Puddles, female Himalayan (16 yrs)
Jasper, male Ragdoll ?? (approx 9 yrs)
Sweet Pea, female silver tabby DSH (approx 7 yrs)
Rose semi feral, a cpietra rescue, female tabby (approx 6 yrs)
Snowball RIP (1991-2005)
In a cat's eye, all things belong to cats.-English Proverb
“While we are free to choose our actions, we are not free to choose the consequences of our actions.” Stephen R. Covey