I used dry weight (instead of cooked weight) to show consistency of fiber content between the different foods that are often bought in a dried form (e.g. beans, oats, lentils, peas). You can dry foods to a consistent point (no water at all), but the cooked weights can vary quite a bit depending on several factors (e.g. amount of heat, duration of cooking, amount of water added, type of heat/appliance used). This variability in cooked weight, due to differences in the amount of water that is absorbed, changes the concentration of fiber. For example, with enough heat and cooking time, oats can absorb quite a lot of water. Depending on how the oats are cooked, 3 oz could deliver quite a different amount of fiber (more water absorbed = less fiber per unit of weight, and vice versa). I used dry weights to make things simpler and to demonstrate a more reliable gauge of comparison in the fiber content of foods that commonly come in a dry form.
Slavin, J. L. (2005). Dietary fiber and body weight. Nutrition, 21(3), 411-418.
Marlett, J. A., McBurney, M. I., & Slavin, J. L. (2002). Position of the American Dietetic Association: health implications of dietary fiber. Journal of the American Dietetic Association, 102(7), 993-1000.
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