Many Americans who are trying to eat more healthfully switched to popcorn for snack time. Then came reports that the popcorn sold at movie theaters can contain as much fat as three to five Big Macs. Confusion now reigns: “Is popcorn a health food, or is it as bad as chips and cookies? Will popcorn help me lose weight or make me gain it?”

Popcorn itself is a nutritious snack choice, containing more fiber than snacks made with refined flour. In the standard three-cup serving (the size of a small mixing bowl), air-popped popcorn contains just 93 calories and less than 1.5 grams of fat. But don’t be fooled by pre-popped products labeled “air-popped.” Although they aren’t cooked with fat, they may be sprayed with fat afterwards, bumping up a three-cup serving to about 170 calories and more than 10 grams of fat.

The confusion really begins when we look at the many kinds of microwave popcorn available. The brand popcorns lowest in fat, like Healthy Choice and Orville Redenbacher’s “Smart Pop” or “Light Natural,” have just 45 to 60 calories and one to two grams of fat in a three-cup serving. But if you choose the “theater style” or “ultimate butter” types, don’t try to convince yourself it’s health food. A three-cup serving (usually a third or less of the bag) of this type of popcorn has 120 to 135 calories and 8 to 12 grams of fat. And keep in mind that the saturated fat listed is not the only part of the fat that hurts your health. Trans fats raise blood cholesterol and may have other undesirable effects, but they are not specifically listed on the label.

If you eat three cups of sugarcoated popcorn or caramel corn, you’re getting about 400 calories. There may be more nutrition in those calories than in the same calorie equivalent of fat-free cookies, but 400 calories is probably more of a snack than most adults need.

Nutritional information is not widely available about the popcorn sold in movie theaters. A few years ago, one report said that the smallest portions (often six cups, or double the standard serving) contain about 20 grams of fat. The large buckets reportedly contain 80 grams of fat, or almost 130 grams if served with added butter. If true, the fat content in that snack would be comparable to three to five Big Macs or six to 10 candy bars.

Whether the popcorn is eaten in the theater or at home, the size of your portion is the major health issue. The nutrition information on boxes of microwave popcorn is often listed by the cup, or is based on a standard three-cup serving. If you eat the whole bag, equal to three to five of these standard servings, the lightest popcorns provide a moderately reasonable 145 to 300 calories. Eating the whole bag of high-fat versions makes the impact greater, of course: 400 to 500 calories and 35 grams of fat.

Make popcorn a healthy choice by choosing a low-fat version. Air-pop regular popcorn; if you can’t get used to it plain, sprit it with one or two sprays of a non-fat, butter-flavored cooking spray. If you prefer microwave products, sample different low-fat options to find the one you like best. Regardless of what you choose, limit your portions. Pour an appropriate amount in a bowl and seal up the rest if you’re not sharing. Or, look for the smaller packages that are sometimes available. When you go to the movies, get the smallest order and share it. Or, better yet, be kind to your wallet and your health by simply concentrating on the movie without snacking your way through it.