Tracking my fitness biomarkers across 3 years of fasting – including results from my 7-, 9-, and 10-day water fasts. Scores dip at the end of every extended fast (56, 63, 82) and rebound back within weeks of refeeding (87, 85, 87).

Fitness Biomarkers

  • Jun 30, 2023 - 85

  • Dec 17, 2024 - 87

  • Feb 11, 2025 - 56 (end of 9-day fast)

  • May 27, 2025 - 87

  • Aug 25, 2025 - 87 (before 10-day fast)

  • Sep 4, 2025 - 63 (end of 10-day fast)

  • Oct 14, 2025 - 85 (after refeeding)

  • Jul 25, 2026 - 87 (before 10-day fast)

  • Aug 6, 2026 - 82 (end of 10-day fast)

  • Aug 18, 2026 - 87 (after refeeding)

Testosterone

Testosterone, ng/dL

  • Jun 30, 2023 - 821

  • Dec 17, 2024 - 969

  • Feb 11, 2025 (9-day ) - 131

  • May 27, 2025 - 564

  • Aug 25, 2025 - 671

  • Sep 4, 2025 (10-day fast) - 495

  • Oct 14, 2025 - 882

SHBG

SHBG, nmol/L

  • Jan 27, 2023 - 83

  • Jun 30, 2023 - 75

  • Dec 17, 2024 - 77

  • Feb 11, 2025 (9-day fast) - 100

  • May 27, 2025 - 60

  • Sep 4, 2025 (10-day fast) - 134

  • Oct 14, 2025 - 60

Cortisol

Cortisol, µg/dL

  • Jan 27, 2023 - 14

  • Jun 30, 2023 - 13.7

  • Dec 17, 2024 - 10.8

  • Feb 11, 2025 (9-day fast) - 14.1

  • May 27, 2025 - 8.5

  • Sep 4, 2025 (10-day fast) - 18.5

  • Oct 14, 2025 - 10.8

Vitamin B12

Vitamin B12, pg/mL

  • Jan 27, 2023 - 580

  • Jun 30, 2023 - 472

  • Dec 17, 2024 - 520

  • Feb 11, 2025 (9-day fast) - 1,548

  • May 27, 2025 - 529

  • Sep 4, 2025 (10-day fast) - 1,605

  • Oct 14, 2025 - 400

Folate

Folate, ng/mL

  • Jan 27, 2023 - 12.6

  • Jun 30, 2023 - 12.9

  • Dec 17, 2024 - 18.8

  • Feb 11, 2025 (9-day fast) - 19.4

  • May 27, 2025 - 18.8

  • Sep 4, 2025 (10-day fast) - 16

  • Oct 14, 2025 - 18.8

Free Testosterone

Free Testosterone, ng/dL

  • Jan 27, 2023 - 11.2

  • Jun 30, 2023 - 9.4

  • Dec 17, 2024 - 10.8

  • Feb 11, 2025 (9-day fast) - 1.5

  • May 27, 2025 - 7.1

  • Sep 4, 2025 (10-day fast) - 5.2

  • Oct 14, 2025 - 10.7