In a method for deriving information about a selected monosaccharide or polysaccharide such as glucose or glycogen, a selected modification such as saturation is made of magnetic resonance at a magnetic resonance frequency of protons of hydroxyl groups of the selected monosaccharide or polysaccharide. Probative water proton magnetic resonance data are acquired while the selected modification is substantially in effect. Information is derived about concentration or density of the selected monosaccharide or polysaccharide based at least on the probative water proton magnetic resonance data.