fatten up vs modify

fatten up and modify both are verbs.

Word	Noun	Adjective	Verb	Adverb
fatten up	No	No	Yes	No
modify	No	No	Yes	No

As verbs, modify is a hypernym of fatten up; that is, modify is a word with a broader meaning than fatten up:

Other hypernyms of fatten up include alter, change.

fatten up (verb)	modify (verb)
make fat or plump	make less severe or harsh or extreme
	add a modifier to a constituent
	cause to change; make different; cause a transformation