The phrase "loses interest in" refers to the act of becoming less engaged or invested in something. There are a variety of synonyms that can be used to convey the same meaning, including:
1. Becomes disinterested
2. Loses enthusiasm for
3. Becomes bored with
4. Becomes disillusioned with
5. Becomes apathetic towards
6. Loses passion for
7. Loses fervor for
8. Becomes indifferent to
9. Becomes jaded with
10. Becomes tired of
All of these expressions convey a sense of emotional detachment and disengagement from something that was once compelling or important. Whether it's a hobby, a relationship, or a career, using synonyms for "loses interest in" can help to add variety and nuance to your writing.