Human trials
Seven-day fasting: strength and endurance respond differently
Effects of seven days’ fasting on physical performance and metabolic adaptation during exercise in humans
Published
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Fasting Free source summary: https://fastingfree.com/education/kolnes-2025-seven-day-performance/
PLAIN-LANGUAGE SUMMARY
What it found
Measured leg strength was unchanged, while absolute peak oxygen uptake fell 13% and exercise performance declined. Lean-mass estimates also decreased.
Keep these limits in view
Completer analysis, no control group and no long-term recovery assessment. Preserved strength does not establish absence of protein loss or suitability for training; this was a different cohort from the 2024 proteomics paper.
Understand the context
- Evidence type
- Small uncontrolled physiological intervention
- Population or scope
- Young healthy adults; no prescription-drug or tobacco use
- Sample or coverage
- 15 initially included; 13 completed, including 7 men and 6 women
- Study duration or data period
- 7-day water-only fast; performance tested on day 6 and body composition on day 7
- Comparison
- Each participant’s baseline; free-living activity with daily laboratory visits and professional monitoring.
- Measured outcomes
- DXA body composition, leg strength, exercise capacity, muscle biopsies and metabolism.
Research terms in this source
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