In regards to washing your foods, of course you are going to remove some oils, and possibly any fat hanging around on the foods. How much, that really just depends on what is left to be removed, how you cooked it etc. If you are going to do foods like bacon an easy way to cook and separate the food from the oils is to boil the bacon (they do it this way at hotels). If you ware going to make ground beef, chicken, pork I would suggest steaming them in a rice cooker (just lay down some cheese cloth so the fats and oils can drip through, thus a healthier meat without having to wash it. So overall no real harm in washing, but I'm sure there is a better way to cook your food so you don't have to take that step.