IPA: /ˈhɛlθfəli/
KK: /ˈhɛlθfəli/
In a way that promotes good health or well-being.
She always tries to eat healthfully by choosing fresh fruits and vegetables.
Healthfully → It is formed from "health" (from Old English *hælu*, meaning wholeness or well-being) and "-fully" (meaning in a manner full of). The word "healthfully" means in a manner that is full of health or promoting well-being.
Think of 'health' as wholeness and well-being, and remember that 'healthfully' means acting in a way that promotes that well-being.