How sweet are Your words to my taste! Yes, sweeter than honey to my mouth! From Your precepts I get understanding; Therefore I hate every false way. (Psalm 119:103, 104)
Some Christians are malnourished spiritually because they invest too little time reading, hearing and meditating upon God's word. Just like our physical bodies require food and water for life sustaining nourishment, our spirit needs the consistent nourishment of the word of God.
To carry the analogy a little further, our bodies need good food and clean water in order to remain physically healthy. We can't be adequately nourished by eating only "junk" food and we can't be adequately spiritually nourished without the regular intake of sound doctrines from the pure word of God; In pointing out these things to the brethren, you will be a good servant of Christ Jesus, constantly nourished on the words of the faith and of the sound doctrine which you have been following. (1 Timothy 4:6)
Our salvation, spiritual growth and well-being depends upon, not only hearing the word of God, but believing, trusting and obeying it; ... In humility receive the word implanted, which is able to save your souls. But prove yourselves doers of the word, and not merely hearers who delude themselves. (James 1:21, 22)
Our physical bodies will eventually fail even with proper nourishment. But our spirits, sustained by the good nourishment of God's word, will be blessed forever. Maranatha!