(64 calories per cup)
"If you struggle with portion sizes, you'll love berries," says Ashley Koff, a registered dietitian in Los Angeles. "You feel as if you're eating more because they're small." And while all berries are awesome sources of hunger-quelling fiber, raspberries have the most (one cup has more than the amount in four slices of whole-grain bread, and twice as much as in one cup of blueberries). And because raspberries are about one calorie apiece, you don't have to worry about measuring them. Just grab a handful, rinse them off, and stuff your face until you're satisfied.
Squeeze more in: Koff recommends dropping frozen berries into chilled brewed tea for a sweet iced tea without added sugar.
(82 calories per medium grapefruit)
Grapefruit diets may have gone out of style with legwarmers and leotards, but these orbs are still one of your biggest diet allies: "They're low in sugar and high in fiber, plus research shows they improve insulin resistance, meaning they make you feel fuller," says David Grotto, R.D., author of 101 Optimal Life Foods. In a study published in the Journal of Medicinal Food, obese adults who ate half a grapefruit before each of their three daily meals lost three more pounds over the course of 12 weeks than those who skipped the grapefruit appetizer.
Squeeze more in: Citrus is a great complement to soy sauce and other Asian flavors. Add grapefruit segments to a stir-fry once everything else is cooked, then stir gently and heat until just warmed.
(95 calories per medium apple)
An apple a day could keep your fat jeans away. The fiber in apples slows digestion, and if your stomach is full of fruit, you're less likely to reach for a sugary snack, says Koff. A medium apple has four filling grams of fiber (most of it's in the skin, so don't peel it!). Bonus: Research has found that inhaling a green-apple scent when a food craving hits may trick your brain into thinking you've already eaten—and result in weight loss.
Squeeze more in: Toss chopped apple, jicama, and celery with olive oil, lemon juice, and honey for a refreshing side salad with a touch of sweetness.
(105 calories per medium banana)
Bananas, with their stick-to- your-ribs texture, are often wrongly accused of being fattening. But new research proves their innocence: Findings reveal that the yellow guys contain "resistant starch," a type of fiber that your body digests more slowly, which keeps blood sugar stable and leaves you feeling satisfied longer, says Grotto. Just be sure to pick a firm banana that's still a little green. Like any fruit, its starches morph into sugars during the ripening process, making the banana sweeter and more caloric.
Squeeze more in: Slice a banana in half, then cover each piece with half a tablespoon of your favorite nut butter and half a tablespoon of cocoa powder. Wrap the pieces in waxed paper and freeze for 10 to 15 minutes for a yummy dessert. (Makes two servings.)
The Lowest-Hanging Fruit
Unsweetened frozen fruit and water-packed canned fruit are worthy stand-ins for fresh produce. But if you're watching your waistline, avoid eating dried fruit. The concentrated sugars up the calorie count. Plus, "the fruit is less filling, making it tempting to overeat," says Ashley Koff, R.D.