保健／电脑／冲浪（等等）迷
someone who is extremely interested in a particular subject or activity
You won't be eating burgers with Tom - he's a complete health freak.
She's a fitness freak - running or working out every day.
In his teens he was a computer freak and, left to his own devices, stayed in his room all day.
Chris has turned into a gym freak of late.
He'd assumed I was some kind of yoga freak just because I went to two classes a week!
See also: freak noun (ENTHUSIASTIC PERSON)