Complex sentence: Metabolic typing is the term for a diet based upon the concept metabolic type that people have unique metabolisms, and that therefore the nutrients and their balance which are appropriate for one person may be inappropriate for a second, and detrimental for a third.
Split into simpler sentences: Metabolic typing is the term for a diet based upon the concept metabolic type. Proponents claim that each person has a unique metabolism, and that therefore the nutrients and their balance which are appropriate for one person may be inappropriate for a second, and detrimental for a third.