My health is excellent and I am full of life.

Vitality shows up in odd places. Not in bloodwork so much as in whether you are currently looking forward to anything.

People who seem full of life tend to have something on the calendar they are mildly excited about. A trip in October. A book someone recommended, still unopened but promising. A rematch with a friend who beat them at something.

That forward lean is both a symptom and a cause. Health makes the appetite possible, and the appetite quietly protects the health, because people who want to be somewhere in October take better care of themselves in August.