I'm a bit of a fanatic about...

Meaning

I'm very enthusiastic and possibly obsessive about...

Examples

• John: You've been spending a lot of time at the gym lately.
• Alice: Yeah, <b>I'm a bit of a fanatic about</b> fitness these days.
• John: That's dedication!
• Alice: I know. Some might say it's excessive, but <b>I'm a bit of a fanatic about</b> staying healthy.