Energy Metabolism
From WaiWiki
The 3 main sources of energy in your body are fatty acids, sugars and protein (disregarding alcohol).
During starvation, utilisation of fatty acids from intracellular lipid droplets is increased, and autophagy mediated.[1] Acute exercise increases lipolysis specifically in the liver, accompanied by increased serum levels of free fatty acid, glycerol and ketone body.[2]