Who doesn't love the combination of a good movie and some delicious popcorn?  It's certainly encouraging when they are also hailed as low-calorie, fiber-rich, whole grain snacks.

But a lot of factors need to be considered to make the best of the crunchy snack. Here's everything you should know:

What is the healthiest kind of popcorn? 

The snack is best for consumption when in its purest form i.e. air-popped popcorn. In this method, dry corn kernels are added into electric poppers. As it heats up, the kernels explode and turn into popcorn. When nothing is added to it, one cup of air-popped popcorn contains 31 calories, 1 gram of protein, 6 grams of carbohydrates and 1.2 grams of fiber. It is also free from fat, sodium, and cholesterol.

"It not only has a lot of fiber, but when it’s popped with very little fat, it’s quite low-calorie, as well. It also has a lot of volume, so it can make and keep you full. And it’s satisfying, thanks to its crunch," explained registered dietician Abby Langer from Toronto, Canada.

Does the same apply to the microwavable kind?

Unfortunately, there have been a few health concerns linked to microwavable popcorn. Have you ever popped open the brown bag of popcorn fresh from the microwave? The smell that hits you is so strong because it contains a number of chemicals.

Experts warn not to inhale it as doing so regularly can increase the risk of a harmful but rare condition known as popcorn lung.

"The steam and some sort of chemical — maybe some vegetable-oil metabolite — comes out," said Len Horovitz, a pulmonary specialist from Lenox Hill Hospital in New York.

Some microwave popcorn bags are also lined with perfluorooctanoic acid, a chemical that has been linked to cancer in animal studies. However, no evidence currently exists to show that it can do the same for human beings.

What is ideal calorie limit and portion size when indulging?

If you happen to visit the movie theater regularly, it's best to note the calories of popcorn served there. Butterless popcorn served at major theater chains was reported to contain anywhere from 200 to over a 1,000 calories depending on the size.

When snacking, a 3-cup serving air-popped popcorn is considered ideal. This portion size contains 1 gram of fat, 3.5 grams of fiber, 2 milligrams of sodium, and manages to stay under 100 calories. However, keep in mind that these numbers can significantly increase when strong flavors are added to the popcorn.

What else should I know regarding popcorn flavors?

Butter-flavored toppings are said to contain a certain amount of trans fat which can increase cholesterol levels in the body. Other strong flavors should also be consumed in limitation, according to registered dietitian Dr. Laura Jeffers from the Cleveland Clinic.

"Sugars burn in the microwave, so sweet popcorn comes from artificial sweeteners," she said, explaining that pre-packaged varieties like caramel are more of a treat and less of a healthy snack. "Things like truffle oil and cheese powders aren’t usually made from truffles or cheese, but from chemical and artificial flavorings."

Light, healthy seasonings are your best bet if you do not want to consume your snack plain. A hint of ingredients like paprika, parmesan cheese, lemon pepper, and powdered ginger are some examples.