In the absence of oxygen, the pyruvates are fermented into lactate, which recycles NADH into its oxidizing form, NAD+. If oxygen is present, the cell can reap much more energy through the oxidative decarboxylation of pyruvate and the citric acid cycle. Pyruvate at the Crossroads A cell can use the product of glycolysis, pyruvate, in several metabolic pathways besides decarboxylation.
Turns out the old notion of eating a meal every three to four hours to ramp up oneâs metabolism wasnât exactly perfect advice. In fact, how frequently someone eats has little to do with the speed of their metabolism.
Adrenalin levels are increased so that we have plenty of energy to go get more food. For example, 48 hours of fasting produces a 3.6% increase in metabolic rate, not the dreaded metabolic âshut-downâ. In response to a 4 day fast, resting energy expenditure increased up to 14%. Rather than slowing the metabolism, instead the body revvs it up.