Comprehensive Review • 2026 • Noakes and colleagues; Endocrine Reviews
Research Summary
This comprehensive review re-examined more than 100 years of evidence from over 160 studies on carbohydrate intake, exercise metabolism and physical performance. The authors challenge the traditional view that depletion of muscle glycogen is necessarily the main cause of fatigue during prolonged exercise. They argue that exercise-induced hypoglycaemia — falling blood glucose during prolonged activity — may be a more important signal associated with exercise termination. Carbohydrate consumed during exercise can preserve blood glucose and improve endurance performance, including when muscle glycogen is already low. The review also highlights evidence that fat-adapted athletes can sustain high rates of fat oxidation and comparable exercise performance despite lower carbohydrate oxidation. The authors conclude that a major benefit of carbohydrate intake before or during prolonged exercise may be the prevention of exercise-induced hypoglycaemia, particularly during efforts lasting more than about two to three hours or when the liver cannot maintain sufficient glucose production.
Evidence and limitations: Broad narrative review spanning more than 160 studies and over a century of research. It offers a substantial reinterpretation of established sports-nutrition thinking, but it is a review rather than a new randomised trial, and several conclusions challenge prevailing interpretations and should be considered alongside the wider evidence base and sports-nutrition guidance.
Source reviewed: 4 October 2026. This summary is independent of the publisher.