You should eat healthy food to keep healthy. You should eat healthy food to keep healthy.
She exercises every day to keep healthy. She exercises every day to keep healthy.
In order to avoid diseases, we need to live a healthy life. We need a healthy life to avoid getting sick.
The doctor advised him to live a healthy lifestyle. The doctor advised him to live a healthy lifestyle.
Note that "healthy" can be used as adjectives and adverbs, but its part of speech in a sentence depends on the words it modifies. If it modifies a noun, then it is an adjective; If it modifies a verb, it is an adverb.