Today I will tell you a little about what I have learned on the subject of commercial cat food.
My kitty cat Sara has always been a fat feline. She is the kind of cat strangers stop on the street and say "thats one big cat." for the first four years of her life she was about 13lbs. She could groom herself, she would play. When I went to college she began to get really really fat. She gained 5 pounds! By the time I moved her out to California she exceeded the maximum amount weight to put her in the cabin, and she def wouldn't fit under the seat. I had to put her in Cargo. I put Luna down there too so they wouldn't be separated and then ran through all the horrible things that happen to cats involved in plane travel for the entire 6 hour flight. I vowed that when we moved back, Sara would fit under the seat.
I took them to a Vet for their annual and he sold me some prescription diet r/d wich is the current way to get cats to lose weight. I was feeding her a 1/2 c. a day. She was miserable and still not getting any thinner. I turned to the internet...
Cats are obligate carnivores. Most animals on this planet are omnivores. Dogs, bears, dolphins, etc. are omnivores that are often thought of as carnivores because of their physiology, however they have the ability to digest matter that is not meat, for instance, rice. A dog can digest rice, and get some nutrients from it, a cat can't. When cats became popular as house pets a few decades ago, the pet food industry set out to make "cat food" what they did was take some dog kibble, throw extra taurine in it, and sell it to you. Unfortunatly for out kitty friends that kibble is poor nutrition. To make the kibble into hard crunchy shapes they must be made out of carbohydrates. They are cooked at such high temperatures the nutrients are destroyed, even the all important taurine. The pet food companies pack it up put the AFFCO approval on it, and tell you its all your cat needs, and please provide fresh water at all times. This couldn't be farther from the truth.
Cats cannot digest the kibble because there is 35%-50% carbohydrates in them, versus the 3%-8% they are prepared to consume. These carbs provide plant based protein which omnivores like us can synthesize into usable protein, our cats just poop it out and go hungry. The second big problem with kibble is that it is far too dry for cats. They evolved in north Africa and as such have developed to get almost all their water from food. They have very little thirst drive. If you see cats drinking water, you know that they are already quite dehydrated.
The problems that this diet causes for cats are numerous. However many cat diseases that have appeared in the last 20 years are easily treatable by switching cats to high quality wet food with no grains, or a raw meat diet.
I started to feed Sara wellness cat food and within three weeks, she could lick her own butt. She weighs in now at 13-14lbs. The vet's target weight for her was 15lbs.
You could listen to me or you could go to this vet's website, catinfo.org. If you are of a scientific turn of mind I highly recommend the article by Debra L. Zoran published in the Journal of the American Veterinary Medical Association. A great book on the subject is Your Cat: New secrets to a longer stronger life. Also I made a list of cheaper (supermarket brand) wet food with acceptable carbohydrate, water, and sugar levels if you are interested, I'll post it.
I cannot stress enough to you pet owners that the best thing you can do for your cat is march over to your food bowl and throw the kibble away. And if your vet disagrees with you, get a new vet. Thats what I did.