Fitness Biomarkers
Tracking my fitness biomarkers across 2.5 years of fasting – including results from my 7-, 9-, and 10-day water fasts.
The end of the 10-day fast - Sep 4, 2025
After 40 days of refeeding - Oct 14, 2025
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