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Effects of seven days’ fasting on physical performance and metabolic adaptation during exercise in humans

Author

Listed:
  • Kristoffer J. Kolnes

    (Norwegian School of Sport Sciences
    Odense University Hospital)

  • Emelie T. F. Nilsen

    (Norwegian School of Sport Sciences)

  • Steffen Brufladt

    (Norwegian School of Sport Sciences)

  • Allison M. Meadows

    (University of Cambridge
    National Institutes of Health)

  • Per B. Jeppesen

    (Aarhus University)

  • Øyvind Skattebo

    (Norwegian School of Sport Sciences)

  • Egil I. Johansen

    (Norwegian School of Sport Sciences)

  • Jesper B. Birk

    (University of Copenhagen)

  • Kurt Højlund

    (Odense University Hospital)

  • Janne Hingst

    (University of Copenhagen)

  • Bjørn S. Skålhegg

    (University of Oslo)

  • Rasmus Kjøbsted

    (University of Copenhagen)

  • Julian L. Griffin

    (University of Cambridge
    University of Aberdeen)

  • Anders J. Kolnes

    (Oslo University Hospital
    University of Oslo)

  • Stephen O’Rahilly

    (University of Cambridge)

  • Jørgen F. P. Wojtaszewski

    (University of Copenhagen)

  • Jørgen Jensen

    (Norwegian School of Sport Sciences)

Abstract

Humans have, throughout history, faced periods of starvation necessitating increased physical effort to gather food. To explore adaptations in muscle function, 13 participants (7 males and 6 females) fasted for seven days. They lost 4.6 ± 0.3 kg lean and 1.4 ± 0.1 kg fat mass. Maximal isometric and isokinetic strength remained unchanged, while peak oxygen uptake decreased by 13%. Muscle glycogen was halved, while expression of electron transport chain proteins was unchanged. Pyruvate dehydrogenase kinase 4 (PDK4) expression increased 13-fold, accompanied by inhibitory pyruvate dehydrogenase phosphorylation, reduced carbohydrate oxidation and decreased exercise endurance capacity. Fasting had no impact on 5’ AMP-activated protein kinase (AMPK) activity, challenging its proposed role in muscle protein degradation. The participants maintained muscle strength and oxidative enzymes in skeletal muscle during fasting but carbohydrate oxidation and high-intensity endurance capacity were reduced.

Suggested Citation

  • Kristoffer J. Kolnes & Emelie T. F. Nilsen & Steffen Brufladt & Allison M. Meadows & Per B. Jeppesen & Øyvind Skattebo & Egil I. Johansen & Jesper B. Birk & Kurt Højlund & Janne Hingst & Bjørn S. Skål, 2025. "Effects of seven days’ fasting on physical performance and metabolic adaptation during exercise in humans," Nature Communications, Nature, vol. 16(1), pages 1-14, December.
    • Handle: RePEc:nat:natcom:v:16:y:2025:i:1:d:10.1038_s41467-024-55418-0
    DOI: 10.1038/s41467-024-55418-0
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