Our cat has lost weight and too fast any advice

Hi everyone.
My wife and I need to ask what is happening with our best friend Gobbles. He has lost weight fast. About 3lbs in a little over 2 months, his weight normally was 13.5lbs. It is now 10.5lbs. He is normally a pretty healthy guy.
He has not been as active as usual and seems to be sleeping more during the day. He is 8 yrs old.
He hasn't been pooping regularly and we have changed him to a high fiber and high calorie diet, but we're not sure how it will work.
I started feeding him treats names whiskas temptations. But since noticing his weight loss have stopped..probably about 1 month with no treats now.
He eats only dry food and my wife has fed him the same Costco adult cat food his whole life. Being 8 years old now we have begun feeding him senior cat food.
His weight has gone down so much that when i pet him I can feel his ribs, shoulders, back, hind legs .
I took apart one of his most recent poops and it had some hair and also what seemed to be like an outter layer to it of hard poop, then spongy poop inside. I rolled it around between my fingers and it rolled between them. Like a spongy long sort of thing. I checked for worms but couldn't see anything resembling them.
We are trying to get him pooping more but he is only going every couple of days.
We brought him to the vet and she checked his stomach with her hands but was inconclusive. Then they took a blood analasys and that was inconclusive also.
So we then decided to keep him home and try feeding him fiber food and high calorie.
He is usually a really silly cat. Very happy. But this may have all been a lot for him..he's not like his normal self.

I REALLY appreciate any advice you all out there could give us. I myself don't have a lot of cat care experience.
My wife is very worried its cancer, I thought it was worms. His stomach isn't much potted but its the "fattest" part on him. We're just really not sure where else to find answers.
Thank you so much for reading all of this! Hope to hear from you soon.
- m+r

Losing 3 pounds in 2 months is definitely a sign that something is not right.  WHEN did you change his food?  Was that the beginning of the weight loss?  Maybe he simply doesn't like the new food .  Cats will actually starve themselves sick rather than eat something they don't like. 

What do you mean his bloodwork was "inconclusive"?  Was your Vet looking for something specific?  Did she check for diabetes, kidney disease, Thyroid Issues?  This weight issue could be any of those, or none of them.  Do you have copies of the blood work?  Were any of the values high or low?  Is he eating normally? 

BTW. it is normal for their  poop to have hair in it.  They consumer large amount of hair everyday as they groom, and what goes in must come out.  The proper exit path is actually out the back rather than out the front   I would take that as a good sign.  But the weight loss is still troubling.  So is being less active.

Now, being on a higher fiber food isn't necessarily always good.  It can bulk up the stool and for some cats that can make pooping more difficult.  Some people actually add canned pumpkin to their cats food (of course, it easier to do that if it's CANNED food) .  Pumpkin is a form of fiber, but it doesn't bulk up the stools like some fibers.  Dry food can cause constipation, particularly as cats get older.  If possibly, maybe you can try to feed your guy some canned food, and try even adding a little water to it. (AND canned pumpkin if he'll eat it...maybe just a teaspoon per meal).  That should help keep him regular.  NOT pumpkin pie mix, just plain old pumpkin. 

Back to the weight loss...did your Vet offer any guesses?   How is his appetite?  Does he seem nauseated?  There are medications that can be given to a) increase his appetite, and/or b) help with nausea if that seems to be a problem.  What did they suggest as "next steps"?  Surely you have a follow-up visit scheduled?  If they just sent you home and threw their hands up in the air and said "we don't have any idea and don't know what to say", then I would be looking for a new Vet .  Sometimes you can't figure it out immediately, but, by golly, a good Vet will certainly do something to TRY, besides take some blood and poke around and say "inconclusive". 

I lost my beloved cat when she suddenly lost 8 ounces, her electrolytes were "off" according to the vet and within 2 days she went into  kidney failure and was dead. Rapid weightless in a cat in VERY VERY serious. Get a second
opinion.

Thank you for your support and I'm sorry to hear about your loved one passing due to kidney failure.
The vet did surgery today on him. They did a exploratory surgery. They found that his stomach was not moving , it should move when they looked inside. Also his liver had damage called fatty liver, where from not eating it was damaged. Other than that they did not find a foreign body or any clogged stomach. He is spending the next few days in the vets care. We might bring him home tomorrow afternoon if we're lucky.

Thank you greenjeens for your concern! It would seem that after all the worry we found out what it was. We will be putting him on a steroid for his stomach and appetite stimulant to get him eating. Thank the lord he did fine in surgery.
Again I'm sorry to hear about your cats kidney failure, it worry's me that it happens so fast with hardly any signs.

Thank you for your concern y'all! Looks like he will be fine, he's resting and well.

Just be aware that Fatty Liver can be deadly if not taken seriously.  It may necessitate a feeding tube...often it does.  Even with appetite stimulants, cats often simply cannot eat on their own if they have Fatty liver Disease (also called Hepatic Lipidosis).   And even once they DO start eating on their own, you really have to watch them to make sure they eat enough and don't backslide until they have fully recovered.  BTW, he may turn yellow before he completely recovers.  That's jaundice.  It may be working it's way up to the surface already, so don't let it scare you.  Most cats with this do get yellow, especially  noticeable around their ears and gums.

I would imagine he will be getting liver supplements as well as the steroids and appetite stimulants.   Plus probably some anti nausea medications as well.   Did they say WHY they think his stomach stopped moving?  Something most have caused that

that he heals well from the surgery, and that's it's just a "mild" case of Fatty Liver .  No matter, though, he will still need liver supplements to heal it.  Luckily, the liver is one organ that CAN heal. 

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