Whether popcorn is "healthy" depends how you eat it.

In its purest form -- that is, plain air-popped kernels -- it's a healthy, whole-grain, antioxidant-rich snack food that comes at a pretty low-calorie cost for those who like to mindlessly nibble: A three-cup serving of air-popped popcorn has only 93 calories, 1 gram of fat and close to 4 grams of fiber.

But movie theater popcorn, which is popped in coconut oil before salt and a "buttery topping" are added, is a distant cousin to its more clean-living relative.

According to a report from the Center for Science in the Public Interest, a medium bucket of popcorn holds 20 cups and contains 1,200 calories, 980 milligrams of sodium and 60 grams of saturated fat, or about three days worth. Even if you ate only 3 cups (probably unlikely), you would still consume about half a day's worth of saturated fat.

If you're buying pre-popped popcorn in supermarkets, be sure to check nutrition labels, as serving sizes, sodium and sugars vary. Kettle corn, for example, can have up to 4 teaspoons of sugar per 1¼-cup serving.

But Skinny Pop's original popcorn has zero grams of sugar and close to 4 cups per serving. Sodium levels can range too, from 75 milligrams for Skinny Pop's original popcorn to 310 milligrams for Wise's white cheddar version.

If you're popping at home in the microwave, choose light or lower-fat versions. Limit the amount of salt and butter you add, and consider adding herbs such as basil, oregano or red pepper flakes -- or even Parmesan cheese instead.