kittten with voracious appetite doesn't gain weight

Hello,

Theo is 3 months old now, fully weaned, 2 of 3 vet visits out of the way, and clean bill of health.  He has been wormed and had a fecal test...

Theo eats all the time.  We have three adult cats and he has no hesitation in pushing the biggest and meanest out of the way so he can get to a food dish.  He will eat all his food and all theirs too... He doesn't care for the kitten food, and will push all the other cats out of the way so he can eat their food, but once all that is gone, he will go eat the kitten food as a last resort.  He is a high energy cat, keeping the three adults worn out with no problems- but the suggested kitten feedings is a mere appetitizer for poor Theo... For the most part,  he is a healthy looking cat, bright eyed and rambunctious, but he is just so skinny.  He is growing taller, but is not filling out at all... when do little cats start getting fat?

Can you add a photo?

several, but they don't show how skinny he is.  When you pick him up, he is lighter than air. 

the above picture is from a week or so ago... he seems to be getting taller, and skinnier.  I will see if I can get my daughter to take a pic of him standing up and holding still (like that ever happens).

Three months is young.  Give him all he wants.   Sounds like he is burning calories playing and he will need more food as he gets bigger.  I suggest ordering food on-line at a discount.  He should be fed more often than the adult cats.  At least 4 times a day.  I think they start filling out around 8 months.

Are the other cats getting enough food?

Yes, we feed extra.  All 4 cats have been members of our family for less than a year. Snowy came from the Shelter after she was abandoned at the lake and found near death  and Buttercup is a stray/feral and don't know her back story... she adopted us after getting pregnant. Tati we got from a lady off craigs list to be a companion for Snowy.  Anyway, Theo and Buttercup get the back half of the apartment, and Tati and Snowy get the front half.  Buttercup is Theo's momma, and she is very food aggressive, and territorial.  We are still working on getting Buttercup and the other cats to get along.  She at least does not try to kill them everytime she sees them now, but they still cannot be left alone.  In addition to their twice daily wet food, there is dry food (adult and kitten) in both halfs of the apartments 24/7... we also fill a couple treat toys every morning for them to play with thorugh the day while I am at work, along with bits of turkey or other cooked meat we feed them to try and get a positive association going on when we have shared space time.  Theo goes back and forth between both halves of the apartments - he gets along with everyone, so he gets fed with Buttercup - who my daughter feeds, and then again with the other two, who I feed.  The resident cats don't usually eat all their food in one sitting.  Usually they eat, then go off for a bit and come back and graze on whats left, but if Theo or Buttecup get out, there won't be anything left.  So, if a food dish ends up empty, we are never really sure who got the lions share, so if someone asks to be fed, then we feed. At this point, no one is overweight (except Buttercup, a tiny bit, but she was practically starved when we got her, and pregnant on top of that.  Her food aggressions is getting better and I think she is starting to feel confident that there will be enough food and for us right now, that is more important than putting her on a diet.