When you cook any kind of meat, there is always some weight loss. This is because the water in the meat gets released and evaporates during the cooking process. The amount of weight loss will depend on how you cook the meat. For example, if you fry it, there will be more water loss than if you bake it. In general, you can expect to lose about 20-30% of the weight of the raw meat when you cook it. So, if you start with a pound of raw ground beef, you'll end up with about 12 ounces of cooked beef.