I too am no expert....but like Karky I keep my ears & eyes to the flow of information. Here's what I can offer as part of my understanding:
Fat is the body's means of storing energy. When you eat and the body determines there is an excess of blood-sugar, the pancreas releases insulin and the insulin acts to usher the glucose into the fat cells for storage. Fat stores energy. I suppose other substances could be stored in fat cells as well...and we've all heard about some of the freaky people from the 60's experiencing strange narcotic episodes based on some of their pre-use drugs being stored and then unexpectedly released later....but that's probably just a wives-tale.
Bottom line, the fat stores energy......little more. What I have heard is that when you're burning a lot of fat you may see a cloudiness to your urine and that's part of the byproduct of fat metabolizing & releasing energy. Wish I could offer more, but that's about all I can think of.