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. 2025 Jul 2;15(1):22805.
doi: 10.1038/s41598-025-05164-0.

Metabolic and hormonal effects of an 8 days water only fasting combined with exercise in middle aged men

Karol Pilis  1 , Urszula Godlewska  2 , Anna Pilis  2 , Krzysztof Stec  2 , Patrycja Dolibog  3 , Marek Kruszewski  4 , Adrianna Kosior-Lara  2 , Romanbek Kalmatov  5 , Wiesław Pilis  2 , Sławomir Letkiewicz  2
Affiliations

Metabolic and hormonal effects of an 8 days water only fasting combined with exercise in middle aged men

Karol Pilis et al. Sci Rep. .

Abstract

Optimal nutrition and physical activity are vital for enhancing physical performance and preventing metabolic diseases like obesity. Recently, interest has grown in long-term fasting, particularly water-only fasting, which involves no food intake and unlimited water consumption. Our study investigated the effects of 8 days of water-only fasting combined with aerobic exercise in 13 middle-aged men, focusing on metabolic, hormonal, and immune changes. Results showed that fasting had a more significant impact than exercise, leading to changes in glucose, uric acid, IGF-1, IGF-2, GH, leptin, and cortisol, improved total antioxidant status (TAS), and reduced lipid peroxidation. While exercise enhanced the effects of fasting on triglycerides, insulin, GH, TAS, PerOX, and IL-6, changes in total protein and lactate were solely due to exercise. Overall, combining fasting and exercise led to a metabolic shift from carbohydrates to fatty acids and hormonal adaptations to stress. These results, although derived from a small group of patients, offer a promising outlook for further research into the effects of fasting combined with physical activity on health and weight maintenance.

Keywords: Fasting; Hormonal changes; Immunity; Metabolism; Physical activity.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests.

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