Whether you're vegan, lactose intolerant or just enjoy the taste of soy, your waistline will thank you for choosing soy milk over the dairy variety. Even nonfat cow's milk -- the lightest kind -- contains more calories than the average plain soy milk. Watch out for some flavored soy milks, however, because these may contain added sugars and significantly more calories than unflavored versions.

Different brands have varying calorie counts, but the average unsweetened soy milk of any flavor has about 80 calories per cup. The average nonfat, unsweetened soy milk has just 68 calories in the same serving. Sweetened vanilla soy milk may contain 129 calories per cup, while chocolate soy milk may contain a diet-busting 153 calories per cup. If you love the added flavor, hope lies in light versions: Light vanilla has less fat and sugar and may only contain 80 calories per cup. Unless marked as light, lowfat or nonfat, soy milk typically contains about 4 grams of fat per cup.