You've already discovered the joys of the 100-calorie microwave popcorn bag (hello, lovah!). It's quick, easy and an excellent source of fiber. But what if you're still hungry? Next time, says Pachella, toss it with 2 tablespoons of isolated whey protein powder. This way, you'll get flavor and protein (a must-have for energy and lean muscle growth). And with all that satisfaction, you'll only be adding about 120 good-for-you calories to your snack.