Weight loss

When I got my cat a month ago, he weighed 25 lbs. The owner said that she would just fill his bowl completely up and let him eat whenever. I'm sure that is why he's obese.

When I got him, I just started to feed him per the directions on the back of his bag of food. He looks and feels like he's lost a little weight since then, which of course would be a good thing for a cat of his size.

My question is how fast can a cat safely lose weight? I know that if they lose weight too quickly they can get fatty liver disease. So far, he is eating and eliminating just fine. He's acting as he usually does, so no concerns there. He has a vet appt at the beginning of February so we can discuss his diet and help him safely lose weight. Should I go back to feeding him the way he was fed before or continue doing what I am already doing?

I'm sure he's probably fine, but I just worry about him like I do with my human babies.

As you are aware, weight loss in cats can lead to hepatic lipidosis which can be fatal and is not easy to treat. His weight loss should be vet supervised. I would take him to a feline specialist for this, since many vets aren't familiar with cat's nutritional needs, which are different than dogs.
I would consider changing him to a low carb cat food, preferably canned. Dry food can't be manufactured without a significant amount of carbs and cats just don't need carbs. The "Catkins" diet is really good for cats. Purina makes a prescription diet that is for weight loss in cats and is low in carbs, but most canned foods are low in carbs and cats do better in other areas on canned. They are not big water drinkers, being naturally desert creatures, and in the wild get most of their water from their prey. So cats may not get sufficient water on dry food. Here is a good site on the protein, fat and carb content of cat foods.
http://www.sugarcats.net/sites/jmpeerson/canfood.html
I would gradually over a couple of weeks change him to canned. Of course, you will have to feed him a lot of cans at first, so he won't lose weight too fast. You might want to wait until he sees his vet to set up his weight loss program. But from my research I would recommend canned for all cats.
Becky

I think Becky has some great advice, for now, imo...you have a vet apt. set up, he's doing well with you feeding him a more normal amt. based on this foods feeding guidelines, I'd not change foods or do a thing differently until you've seen your vet.

I've been slimming my guys down with twice a day feedings of the weight loss food I chose to use, it is a dry food, and it's Nutro Natural Choice Complete Care Weight Management food, I'm very happy with their results, they began to be visibly slimmer in 2 to 3 weeks.

If I don't misunderstand, you've cut him back to a sensible amount, I'd only be concerned if you took a free-fed and over-fed cat down to something drastic like 1/2 cup of food a day!
My approach would be to feed him not the recommended amt for a 25 lb. cat of his current food, but cut it by say 1/4 of that recommended amt.

I do agree with Becky, wet food is generally better, but like the dry I am using as I noted above.