If you start exercising in your 20s, and never stop, it will be so much easier to maintain fitness in 40s 50s etc. The challenge is that the benefits are not yet visible in your 20s (when you’ll probably be healthy and at a proper weight regardless). Gotta lay that foundation for older age though!

EDIT - I misread the comment. It’s never too late to start, just be careful for injuries as that will block your ability to exercise.