What does Unfit apply to?

[Edges]

The Unfit disadvantage says that you lose FP at twice the normal rate. What does this apply to?

Does it apply to Extra Effort? Does it matter if the Extra Effort is in or out of combat? It says it applies to FP lost due to heat. Does this imply that it also applies to FP lost to other hazards like sleep debt, hunger, and thirst? Does it apply to the FP lost at the end of combat?

Thanks.