Do I need to be fit or athletic to start fencing?

No. If you can walk briskly for twenty minutes, you're fit enough for a beginner class, the sport builds the rest. Fencing has no ideal body type: tall and short, heavy and light, fast and patient all win with different styles, which is rare among sports and part of why it hooks people who never clicked with athletics.

Beginner classes are scaled to beginners: you'll learn footwork in short bursts with plenty of standing around learning rules, nobody runs laps. The conditioning arrives invisibly over months of lunges and advances.

This is also why fencing works so well for adults starting cold and for kids who aren't 'sporty': it rewards timing, tactics and stubbornness over raw athleticism, and everyone improves at their own pace.