Soy milk is naturally lower in sugar content than regular milk. Cow's milk has about 12 grams of sugar per cup as opposed to only 7 grams in soy milk. This is why a cup of whole soy milk has only 80 calories, which is the equivalent of skim milk. In addition, the monounsaturated fatty acid in soy milk can inhibit your intestinal absorption of fat, which is another great advantage for weight loss. Drinking soy milk also gives you an extra dose of fiber, keeping your feeling fuller for longer time.