beef up vs alter

beef up and alter both are verbs.

Word	Noun	Adjective	Verb	Adverb
beef up	No	No	Yes	No
alter	No	No	Yes	No

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

Other hypernyms of beef up include change, modify.

beef up (verb)	alter (verb)
make strong or stronger	remove the ovaries of
	become different in some particular way, without permanently losing one's or its former characteristics or essence
	cause to change; make different; cause a transformation
	insert words into texts, often falsifying it thereby
	make an alteration to