As junk foods go, popcorn is on the healthier side. A whole grain, it is relatively low in calories and offers beneficial vitamins and minerals. However, it is possible to have too much of a good thing, even when it comes to healthy snacks. To enjoy popcorn without going overboard, keep your portion size in check and steer clear of rich add-ons.
The amount of calories and other nutrients in your popcorn depends on how it was prepared and which additional ingredients it contains, if any. According to the U.S. Department of Agriculture, 1 cup of plain, air-popped popcorn has about 30 calories, no sugar and no sodium. However, the same amount of caramel-coated popcorn with peanuts has about 170 calories, 19 grams of sugar and 75 milligrams of sodium -- meaning you can overeat it with even a relatively small serving size.
Home, Microwave or Movies
The source of your popcorn also influences its nutritional content. It's tougher to go overboard with homemade, air-popped popcorn since it's so low in calories and high in fiber and complex carbohydrates. Butter-flavored microwave popcorn has more calories and sodium, however, and movie popcorn has even more -- about twice the amount of air-popped. If you're having a small popcorn at the movies, for example, you're eating more than the equivalent of an entire bag of microwave popcorn, which is between 10 and 11 cups' worth. That adds up to 670 calories or more, easily the amount of a full meal.
Fat and Sodium
With additives and flavorings like the classic butter and salt, the fat and sodium content of popcorn can also be cause for concern. According to the Center for Science in the Public Interest, a small movie theater popcorn has the same amount of saturated fat grams as the limit of what you should eat in two full days. A medium size has an entire day's limit of sodium -- 1,500 milligrams.
If you eat your popcorn air-popped whenever you get the urge to snack on it, you don't have any serious reasons to worry about overdoing it. It's still wise to limit your serving size to several cups, however, so you still have room in your meal for other healthy, nutrient-rich foods. When you're chomping on buttered and salted popcorn, be even more careful about your serving size. To minimize your risk of weight gain and cardiovascular problems, limit yourself to about 2 cups.