Cats are carnivores. That's the most important thing to keep in mind when considering what to feed yours.

"Cats are… different from us and from dogs," says Louise Murray, DVM, vice president of the ASPCA's Bergh Memorial Animal Hospital in New York. "When it comes to nutrition, they are very inflexible, and owners must realize that."

Compared to what their owners should be eating, cats need to eat a lot of meat for protein and for fat.

"If we ate like cats, we'd have heart disease by age 20," Murray says. "They are not at all the same as humans and they are not little dogs."

She's explicit about this because it's not uncommon for owners to treat their cats the same way they treat dogs, which can eat a variety of foods and remain healthy.

In fact, Murray notes that dog food can be fatal to cats over time because it doesn't meet their nutritional needs and it's often loaded with carbohydrates, which cats can't process well.