gym rat vs freak

gym rat and freak both are nouns.

Word	Noun	Adjective	Verb	Adverb
gym rat	Yes	No	No	No
freak	Yes	No	Yes	No

As nouns, freak is a hypernym of gym rat; that is, freak is a word with a broader meaning than gym rat:

gym rat: someone who spends all leisure time playing sports or working out in a gymnasium or health spa
freak: someone who is so ardently devoted to something that it resembles an addiction

Other hypernyms of gym rat include addict, junkie, junky, nut.

gym rat (noun)	freak (noun)
someone who spends all leisure time playing sports or working out in a gymnasium or health spa	a person or animal that is markedly unusual or deformed
	someone who is so ardently devoted to something that it resembles an addiction

gym rat (verb)	freak (verb)
	lose one's nerve