The 10 Best Foods for Flat Abs

Berries and Leafy Greens

5. Berries

Most are loaded with fiber, every dieter's best friend. The more fiber you eat -- experts say that it's best to get between 25 and 35 grams every day -- the fewer calories you absorb from all the other stuff you put in your mouth. That's because fiber traps food particles and shuttles them out of your system before they're fully digested. Berries (and other fruits) are also high in antioxidants, which not only help protect you from chronic diseases like cancer but may also help you get more results from your workouts. "Antioxidants help improve blood flow, which can help muscles contract more efficiently," says Dr. Katz.

Try for: At least half a cup daily, or about 30 calories' worth. Don't limit yourself to the usual suspects, like raspberries, blueberries, and strawberries. If you can find them, add boysenberries, gooseberries, and black currants to the mix for excitement.

6. Leafy Greens

Their cancer-preventing carotenoids won't help shrink your waistline, but their low calorie count definitely will. One cup of spinach contains only about 40 calories, while a cup of broccoli has 55 calories and satisfies 20 percent of your day's fiber requirement. Most leafy greens are also a good source of calcium, an essential ingredient for muscle contraction. In other words, they help fuel your workouts.

Try for: Three servings daily. Keep a bag of prewashed baby spinach in your fridge and toss a handful into soups, salads, pasta dishes, stir-fries, and sandwiches. When you get sick of spinach, reach for a bunch of arugula, broccoli rabe, or broccolini, a cross between broccoli and Chinese kale.