Air-popped popcorn is one of your best bets for a low-calorie, low-fat, high-fiber snack, advises "Cooking Light." Unlike many less-than-healthy snacks, popcorn is a whole grain that can help you fulfill the daily grain requirement recommended by the U.S. Department of Agriculture. A 3-cup serving of air-popped popcorn is equivalent to 1 ounce of grains; most adult women need only about 6 ounces of grains per day, while men need around 9 ounces. Keep your popcorn low in calories by avoiding high-fat toppings like butter.
Total Calorie Content
A 3-cup serving of plain, air-popped popcorn contains approximately 93 total calories. For an adult following a 2,000-calorie diet, this amount would supply about 4.6 percent of her daily caloric needs. Whenever possible, eat popcorn without added butter to cut down on saturated fat. Instead, use a drizzle of olive oil or cooking spray and toss the kernels with low-sodium seasonings to add flavor without a large amount of additional calories or saturated fat.
Calories from Fat
Plain, air-popped popcorn has very little fat -- only a total of 9.8 calories in a 3-cup serving -- about 1 gram -- are contributed by fat. In addition, each serving of popcorn has less than 1 gram of saturated fat, or 6 percent of the amount a healthy adult on a 2,000-calorie diet should limit himself to each day. Without the addition of a fat source like oil, butter or margarine, popcorn has no cholesterol or trans fats.
Calories from Carbohydrates
In a 3-cup serving of popcorn, 80 percent of the total calories -- or about 19 grams -- are from carbohydrates. Of this amount, 0.21 grams come from simple sugars and 3.5 grams from dietary fiber. An adult man should have 34 grams of fiber each day, while a woman should have 28 grams daily; consuming 3 cups of air-popped popcorn would supply a man from 19 to 30 years old with 10 percent of his fiber requirement per day and a woman in the same age range with 12 percent of her daily fiber needs.
Calories from Protein
Popcorn isn't rich in protein, but it does contain 3.1 grams, or 12.4 calories from protein, in every 3 cups. That amount is 6.7 percent of the daily protein requirement for the average woman and 5.5 percent of the protein recommendation for the average man. The protein in popcorn is not complete -- it doesn't provide all of the amino acids that your body needs. By eating a wide variety of foods daily, however, you can consume adequate protein even without eating animal-based products, says the Centers for Disease Control and Prevention.