My cat eats the litter every time after I clean it?

Hello everyone, 

My cat is a little a year old and recently he has been eating the litter every time I clean it. Usually when I clean it, he'll think it's a game and come play and try to get the scooper from outside the box. Then once I am done, he will peek his head in, kick the litter around a little bit, and then either just eat it out of the box or eat it out of his paws. So today, I put him inside the bedroom and closed the door while I cleaned it so he wouldn't be around. He came out, went to his food bowl and ate a little and then went to the box and started eating it again! Now, he is sitting in front of his box just staring at it. 

I don't know what is going on or why he is doing this. I thought he might have just thought it was a toy, but from today when he wasn't even around for me cleaning it, he came out and started doing the same thing. It just doesn't make sense! Does anyone have any experience with this? 

I should add, this started happening about two weeks ago. He's still been eating, drinking, urinating, and still defecating. Also, he's still been acting energetic and playful. He sleeps a decent amount, but he has always been like that. I have been using clumping litter, and that is what worries me about it because I've read some things online about it possibly causing a blockage if the cat eats enough. I'm going to go buy a different litter this weekend. Any recommendations on what kind is the most safe for him if he eats that too? Also, my cat is a pretty big cat, he weighs 14 pounds. 

I just took him to the vet for a checkup about three weeks ago. The vet said he's very healthy and everything was all good. Does anyone know why he possibly could be doing this? Should I take him to the vet again? Any help is very much appreciated!! Thank you. 

Is he getting enough to eat? My first thought would be a nutritional deficiency.

Also what food is he on?

Yes, he eats a lot. The last time I took him to the vet, the vet actually told me that he is a little overweight and actually needs to lose weight. He is on Science Diet Adult for indoor cats. 

In the past couple hours, he constantly kept going back and trying to eat it, unless I would distract him by playing. After about the 10th time of me trying to get him to stop going to his litter box, I let him peek his head in. (in case he actually had to use the bathroom). Immediately I heard him eating it. So I did something super weird and I took the litter I had just cleaned and put some of it back in the box so he won't eat it overnight while I sleep. After I did this, he went to the box and smelled it and walked away. He hasn't tried to eat it since I did that. 

I should also add that in the past he has torn up carpet and ate some threads, and would chew and eat cardboard if any boxes were left out. He hasn't done the carpet thing for a while and I put all cardboard away so he wouldn't eat it. 

It does sound like a nutritional deficiency to me. Science diet is actually not a great food from what I've read.

Okay thank you for your help. What food would you recommend? I've heard science diet is not that good either so I tried switching him to Blue Buffalo, but he would not eat it. Also, do you think it is serious where I should schedule a vet visit even though I recently took him? Or do you think a switch in food would do the job? Thank you again for your help. 

From what you described your cat might have pica, and eating disorder where the patient eats non food objects. A nutritional deficiency can cause it.

I do believe you should contact the vet before making changes so they can work with you on this.

Also, do you think he will be okay since he has consumed the litter? I know it can't be good, but I don't know if it requires immediate medical attention or anything. The website says it shouldn't harm him, but I've read some really bad stories online about clumping litter and how it can be deadly for the cat if he eats it.  

If he's acting himself he should be fine. I think issues arise if it continues over time. If it's only a tiny bit he's eaten he will probably poop it out.

Okay. Thanks so much for your help!