life style vs fashion

life style and fashion both are nouns.

Word	Noun	Adjective	Verb	Adverb
life style	Yes	No	No	No
fashion	Yes	No	Yes	No

As nouns, fashion is a hypernym of life style; that is, fashion is a word with a broader meaning than life style:

life style: a manner of living that reflects the person's values and attitudes
fashion: how something is done or how it happens

Other hypernyms of life style include manner, mode, style, way.

life style (noun)	fashion (noun)
a manner of living that reflects the person's values and attitudes	characteristic or habitual practice
	consumer goods (especially clothing) in the current mode
	how something is done or how it happens
	the latest and most admired style in clothes and cosmetics and behavior

life style (verb)	fashion (verb)
	make out of components (often in an improvising manner)