In this conversation, Professor Tim Noakes contradicts the long-standing belief that carbohydrates and muscle glycogen are the primary drivers of athletic performance. Drawing on his decades of research, he argues that muscle glycogen is often overrated and that endurance and high-intensity performance are more closely governed by the brain’s access to circulating glucose, largely supplied by the liver.

Noakes presents a two-pool model in which maintaining blood glucose—not maximizing muscle glycogen—determines fatigue and performance, helping explain why carbohydrate loading often shows little benefit in well-controlled studies. From this view, fat oxidation, liver glucose output, and metabolic flexibility play a far larger role in fueling performance than the high-carbohydrate paradigms suggest.