Published on 13 Dec 2019
In regards to systemic hormones, not much actually. The body tends to have a very similar hormonal profile after solely fat ingestion when compared to not ingesting anything at all.
Fatty acids, after being digested, route around the body in chylomicrons (transport systems) and get deposited in cells. The enzyme lipoprotein lipase (LPL) is usually pinpointed for its role in taking the glycerol backbone off fats so they can diffuse into fat cells.
While fats are entering the cell, they can also be used up for energy in beta-oxidation processes. There is no real hindrance to fatty acids being used for fuel when fats are ingested.
So without carbs, fats both enter cells and are burnt for energy.
(It should be noted that this 'lack' of systemic hormonal response is similar to fasting. The only difference is that in the ingestion of fats there is a influx and efflux of fatty acids; during fasting there is only efflux)