There are many words that can be used as synonyms for the phrase "obsessed with." These include "fixated on," "hooked on," "consumed by," "engrossed in," "preoccupied with," "addicted to," "devoted to," "captivated by," and "enamored with." Each of these words conveys a similar level of strong attachment or interest in something. Whether it is a hobby, a person, or a particular topic, these words indicate that the individual is consumed by their feelings towards it and may prioritize it above other aspects of their life. Regardless of which synonym is used, the message is clear: this person is fully invested in what they are obsessed with.