Peanut butter is an excellent source of monounsaturated fats, which help maintain healthy cholesterol levels. It also contains protein and fiber, and tastes delicious spread onto apple slices or whole-wheat toast. The high fat content means that peanut butter is also high in calories, however, so eating more than a single serving can quickly put a damper on your diet.
One recommended serving of peanut butter is 2 tablespoons, which is about the size of a ping-pong ball. That serving contains about 188 calories, 145 of which come from fat. Thus, peanut butter is more than 75 percent fat; the 2010 Dietary Guidelines for Americans recommends limiting fat to just 20 to 35 percent of total calorie intake. While this doesn't mean that peanut butter is off-limits, it does mean you should avoid larger servings and balance it with foods that contain little or no fat.