Treat it as both (physics/mathematics & physiology):
Mechanical, Thermal Dynamic (electrical) & Chemical
Muscle to adipose mass in ratios if you have a lot of adipose tissue; slightly increasing muscle which is not going to be the same as in the volume of adipose fat (if you have a lot of it) will burn fat and at the same time oxidize sugar/carbohydrates when you eat it or right after you eat it especially when you do the ketogenic diet.
Muscle volume is like the inertia of physics, the more you have, the more you increase the acceleration of oxidation along with low insulin and less accumulation of lipid droplets to replenish pre-existing adipose cells (fatty acid turnover-pool) and the creation of new ones from left over stem cells of previously oxidized fat cells which are created from excessive sugar/carbohydrates and sometimes dietary fats[1]!
Fed or fasted it does not matter, skeletal muscle volume does matter exponentially?
References:
[1] “…For regular dietary fats, once they are digested, they enter the circulation and participate in what is called ‘fatty acid turnover.’ Whether fed or fasted, the body is always releasing, burning, and storing fat. When insulin is high, storage predominates, but turnover continues. When insulin is low, release and oxidation predominate. If you eat fat along with a lot of carbohydrates, it is prone to be stored. When fat is consumed in the context of a well formulated ketogenic diet, it — along with fat released from adipose stores — is prone to be burned. But once digested and absorbed, dietary fat and stored fat enter the ‘turnover pool’ and are in a constant state of mixing. …More
Note: “prone to be burned” skeletal muscle volume?