Cat Weight Issue

Question
Here are the facts:

I have a 7 y/o cat who weighs 17 lbs.
I have a 2 y/o cat who weighs 13 lbs.

Eight months ago I had to move into a fourth floor apt and they are no longer able to go outside. They've become bored and lazy (like their owner). Before we moved they were 12 and 10 lbs respectively. I am having a really hard time getting them to play as they hate it here and are depressed. I know what can happen to overweight cats and it would kill me if they got sick and I knew I did it to them.
I currently feed them Purina Cat Chow for Indoor cats. I'm on a VERY tight budget. I offer them plenty of clean water at ALL times.
Can you tell me how much, and when I should feed them (I'm able to feed them separately, as the 7 y/o is a HOG)  Also... the 2 y/o has vomiting issues w/ hairballs and I often have to give her the hairball remedy in a tube. Please help with any advice you can offer.

Worried Kitty Mom In CT

Answer
Worried Mom,

Here is an excellent article for you to read on obesity in cats: (copy and paste or type the whole link into your address bar)
http://www.thepetcenter.com/imtop/catweight.html

A way to get cats to play, even lazy ones, is to get a pet laser light from somewhere like PetSmart. They are inexpensive and the hunting urge stikes them they see that 'little red bug' on the walls or the floor.

Something else I use to play with them that they can't resist is a long zip-lock tie. They are the plastic ties you wrap around something, put the end into the other end and pull. You pull a straight one in from of them and they go for it but they can't catch it because it slips through their paws. Even my old cats will go after them.

Another thing you can do is take them outside on a harness. Here is a link on how to harness train them:
http://www.hdw-inc.com/leashtraining.htm

I hope this helps.