When you're trying to lose weight there's nothing more affirming than seeing the number on the scale move steadily down, day after day. But what happens when your weight loss stalls?

You stop feeling so motivated-which can lead to slip-ups and the sort of downward spiral you don't want. Don't let that happen. Instead, give yourself credit for hitting this next level, then change your game plan. Try one of these tried-and-true methods for breaking through a stubborn weight-loss plateau:

Choose single-portion foods: Study after study shows that people tend to underestimate portion sizes and the calories they consume. Remove the guesswork by reaching for foods that make it easy to stop at one portion-we're not talking just 100-calorie snack packs, but rather things like English muffins (versus a loaf of bakery bread), apples (versus grapes), mini soufflés versus a full-size quiche that begs you to take just another tiny sliver.

Switch your snacking habits: One new study suggests that it may not be portion size-or high-cal food choices-that are causing us to consume far too many calories, but rather how often we're eating. Compared to the late-1970s, Americans today are eating 29 percent more calories through snacks. Yes, there's the perception that many mini meals may be better than a few large ones if you're trying to shed pounds-but not if it adds up to consuming more calories overall. (Don't miss: The truths behind 12 other nutrition and food myths!) One eating pattern that often works well for dieters: three satisfying meals, plus two small snacks-one midmorning and one midafternoon. For ideas, check out these satisfying-100 calorie snack recipes.

Pump up the fiber: Fiber, which helps you to feel full on fewer calories, can help jump-start your weight loss. In one two-year study in the Journal of Nutrition, boosting fiber by 8 grams for every 1,000 calories resulted in losing about 4 1/2 pounds. Shoot for at least 25 grams a day from a variety of vegetables and fruits, beans (and other legumes, such as lentils) and whole grains.

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