[LisaS]

Of course you can weigh fluids. It doesn't "throw" the results at all assuming that your lookup table allows you to specify weight as well. For liquids very like water, you can probably assume a pint = a pound or a liter = a kilogram.

Weighing raw or cooked entirely depends on what your tables allow you to lookup and how you measure out your serving portion. If you weigh out 1 chicken breast at 4.5 ounces and that is the one that you eat, go for it. If you cook 5 breasts on the grill and have no idea what each one weighed pre-cooking, you should weigh the one that you take to your plate. If you weigh out 2 oz pasta, cook it and eat it all as your portion, you are fine. If you cook 1 pound of pasta and serve yourself "about 1/8 of the pot", you should probably weigh the serving that you actually take. If you make a casserole, measure all the ingredients and divide by the number of squares you cut in your casserole dish.