Can a modified ketogenic diet be a nutritional strategy for patients with McArdle disease? Results from a randomized, single-blind, placebo-controlled, cross-over study

•In this randomized trial, we tested a modified ketogenic diet in participants with McArdle disease.•The diet induced a metabolic shift towards increased fat metabolism.•The diet improved maximal exercise capacity and patient-reported outcomes.•The diet did not convincingly improve submaximal exercise capacity.•Possible nutritional strategy in motivated patients but should not be standard of care.