weight gainer vs doer

weight gainer and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
weight gainer	Yes	No	No	No
doer	Yes	No	No	No

As nouns, doer is a hypernym of weight gainer; that is, doer is a word with a broader meaning than weight gainer:

Other hypernyms of weight gainer include actor, worker.

weight gainer (noun)	doer (noun)
a person who gains weight	a person who acts and gets things done