Popcorn

"Because it's super-low in calories, popcorn is the perfect food for those times when you don't want to worry about portion size," says Sharon Richter, RD, a nutritionist in New York City. And it's loaded with fiber, which is crucial for staying slim. In fact, people who maintain a healthy weight consume an average of 33 percent more fiber daily than those who are overweight, according to research.

Eat It Up: Save calories (and money) by getting a basic air popper. One we like: Orville Redenbacher's Gourmet Hot Air Popper by Presto ($25, bedbathandbeyond.com). Pop the kernels with a bit of salt and toss with nuts and raisins for a tasty trail mix.

Nutrition facts per 1 cup air-popped: 31 calories, 1g protein, 6g carbohydrate, 0g fat, (0g saturated), 1g fiber