Peanut butter is quite possibly a perfect food. You can buy it just about anywhere, it's tasty, and a great source of protein.
But beware - not all peanut butters are created equal. You want to make sure you're buying the natural kind - we're talking just peanuts. Other brands you grew up with like Jif and Skippy contain sugar, hydrogenated vegetable oil and a stabilizer to keep the oil from separating. Gross.
In the U.S., peanut butter must contain at least 90% peanuts to be called peanut butter. That's why some companies call theirs peanut spread.
You can buy natural peanut butter at health food stores. Look for the jars that have the oil separated on the top - that's the good stuff. Or some stores sell peanut butter in bulk, so the oil is already mixed in for you.
Fit's Tip: I'll admit - it's annoying when you open the jar, and the oil is separated on the top. When you try to mix it up, the oil overflows and spills everywhere. Try warming the opened jar a little bit in the microwave - then it's easier to mix.