Fitness enthusiast v Athlete

What is the main difference between a sports enthusiast who maintains a high level of fitness for themselves, and an athlete?

Or put simply, what defines an athlete?

Difficult thing. In most cases I would judge it as someone who has gone through a lot of preparation, and actually finished what they set out to do.

Though I suppose it's a different perspective in other peoples minds.

Competition? Athlete being someone who competes in the sport...sports enthusiast being someone who does it just for fun?

enthusiast: a person who is filled with enthusiasm for some principle, pursuit, etc.; a person of ardent zeal: a sports enthusiast.

athlete: a person trained or gifted in exercises or contests involving physical agility, stamina, or strength; a participant in a sport, exercise, or game requiring physical skill.

Descriptions taken from dictionary.com

If that definition is correct I'd much rather be an athlete..