This is cyclic AMP (cAMP). Exercise increases it. C-AMP activates Protein Kinase A (PKA). PKA phosphorylates hormone-sensitive lipase. Stored fat exits the fat cell.
Bear with me. I’m genuinely trying to dumb it down.
Try to remember this:
Increase cAMP = increase PKA = fat loss
Decrease cAMP = decrease PKA = fat gain
C-AMP increases in response to contracting skeletal muscle.
Increases in PKA starve fat.
Decreases in PKA damage the brain.
Eating food decreases PKA.
This is why a weight lifter can eat more calories than she uses and get leaner.
This is why a cardio junkie can eat fewer calories than he expends and get fatter.
This is why strength can predict risk of cognitive decline (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2838435/).
Regulatory proteins make or break fat, LITERALLY. Calories are a post hoc distraction.