Well your body is using fats and muscle for energy during all weight loss. Not sure that there is any quality data that one method or another results in more from one or the other compartment end of day of a complete weight loss program. My WAG is that bigger controller of the body composition impact is the amount and sort of exercise done during the program. If time allows later I’ll try to search some …
Not sure I am understanding the question of the op though.
Digesting fat breaks into into glycerols and fatty acids which get absorbed and transported to cells which use them, for energy (via oxidation in muscles mainly), for synthesis (such as in the liver), so on. They travel in certain packages.
Metabolizing fat also produces glycerols and fatty acids which get transported to cells which use them … which also travel in certain packages.
The process of breaking down the fat that occurs digestively uses lipases that are secreted into the the intestine. Likewise mobilizing fat stores starts with lipase and that cellular lipase activity level is the rate controlling step.
Is that what the op was asking about?