Flesh
Those of the flesh become hungry for when there is a lack of 'fleshly materials'. The result of this is a would-do-anything-to-get-it desperation for the particular fleshly material, such as food, water, or tangible or intangible object or actionable item that results in sin.
Spirit
Those of the Spirit become hungry for when there is a lack of Spirit materials. The result of this is a would-do-anything-to-get-it desperation for the particular Spiritual material, such as the presence of God and the Word of God.
The more of the Spirit a person is the more he is hungry for the things of the Spirit, and must have a regular intake otherwise he will become hungry and desperate.
Important questions
1. When was the last time you were desperate for fleshly materials?
2. When was the last time you were desperate for Spiritual materials?
3. Has your Spiritual materials intake been increasing or decreasing in the last 2 years?
"Those who live according to the sinful nature have their minds set on what that nature desires; but those who live in accordance with the Spirit have their minds set on what the Spirit desires." - Romans 8:5