The study of cellular metabolism is of primary importance to understand molecular mechanisms governing cellular activities. Biologists made (and are still making) a big effort in characterizing numerous metabolic paths, nevertheless experimental results on cellular populations seem to be somehow in contradiction with their models. It is well established that glucose plays a central role in cellular foraging plans and it is known that mammalian cells can digest it mainly through two principal paths, so why don’t they always use the most efficient one among them (where efficiency is meant in terms of ATP yield)? This effect consisting in the choice of the "inefficient" metabolic pathway is known in literature as overflow metabolism and its understanding has immediate practical implications: cancer cells (as well as other fast reproducing cells) manifest it, so its understanding can lead to new diagnostic and therapeutic techniques for cancer.