The fat from the meat drops onto the hot coals and becomes a vapor in the heat, and then redeposits on the steak. Very hot temperatures destroy certain vitamins and may alter the major proteins. Most fried foods can be baked just as easily. Baking temperatures are commonly 350 o F. Frying temperatures begin at 450 degrees and may reach 600-700 during ordinary frying. If fried foods become burned or scorched, temperatures up to 1000 or 1100 degrees may have been reached.
Most people agree that the addition of fat improves the flavor of food.
Usually though, a small fraction of the fat that you normally use would be quite adequate. Adding more fat than you need only leaves the food greasy and adds more calories. It also makes it harder for the body to handle your food. Saute your onions, etc. Try Hash browns in the waffle iron, or in a sprayed Teflon pan with onions and seasonings.