Key to developing a healthy nutrition plan is mastering those Nutrition Facts labels on food and beverage products. Most important of all is paying attention to the Servings Per Container data. Because most product packages hold more than one serving. And the listed facts are only for one serving. Check out this link to learn how to read these labels.
A serving size is not a portion size. A serving is the recommended amount of a certain food to eat. A portion is the amount of food we choose to eat. Be very wary of packaged foods. Almost all of them contain more than one serving. Read carefully the nutrition label. And divide the contents accordingly. For example, if your can of black beans contains 3 servings, separate out 3 equal-sized servings. Then, prepare 1 and save the other 2. The link here provides other guidelines for serving sizes.