Metabolizing the doctrines of the Bible entails Biblical Truth received as knowledge. From there, by faith, knowledge is understood and believed (faith-digested mentally) and is now ready for application in life. Otherwise the knowledge just sits there, in your mind, doing nothing, and remains basic knowledge without understanding or action.
Spiritual metabolism is the Holy Spirit causing Biblical principles to be understood, believed, and applied to life. It is the mechanics for unmerited eternal rewards. The believer needs only to be positive to, and learn, Bible doctrine in the filling of the Holy Spirit as a daily function in the plan of God for each believer.
The unbeliever operates in the sphere of gnosis (knowledge alone that just sits there). He/she has received Biblical information but has rejected these truths. Likewise, the believer can also reject a particular doctrine by disbelief. Gnosis is life in the realm of disbelief while epignosis is the “super-abundant life” (not necessarily prosperity, but joy and peace and fulfillment – the fruits of the Spirit) as the believer advances to maturity.
Bible knowledge not acted upon by faith remains gnosis. By active faith it becomes epignosis. Epignosis is the availability of Bible doctrine for application to the details of life in your PPPG experience.