Endocrine and chronobiological effects of fasting in women

Fertil Steril. 2001 May;75(5):926-32. doi: 10.1016/s0015-0282(01)01686-7.


Objective: To determine whether fasting in women would suppress GnRH/LH drive in a high- versus low-gonadal steroid milieu.

Design: Case-control study.

Setting: Academic clinical research center.

Patient(s): Eleven eumenorrheic women and eleven women taking combined oral contraceptives.

Intervention(s): Seven of the eleven women in each group underwent an acute 72-hour fast. Blood samples were obtained at 15-minute intervals for 24 hours before the fast and during the last 24 hours of fasting.

Main outcome measure(s): Twenty-four-hour profiles of LH, cortisol, and melatonin were assessed. Ovarian activity was tracked with estradiol and progesterone levels, and metabolic responses were gauged by measuring thyroid hormone and beta-hydroxy-butyric acid levels.

Result(s): Fasting increased beta-hydroxy-butyric acid and reduced free thyronine. Fasting in the midfollicular phase had no effect on LH pulsatility or on FSH, estradiol, or subsequent luteal-phase progesterone levels. However, fasting elevated cortisol and resulted in a phase advance in melatonin secretion of 81 minutes in both the midfollicular and luteal phases.

Conclusion(s): Fasting in women elicited expected metabolic responses and apparently advanced the central circadian clock without compromising reproductive function.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3-Hydroxybutyric Acid / blood
  • Adult
  • Case-Control Studies
  • Circadian Rhythm / physiology*
  • Cluster Analysis
  • Estradiol / blood
  • Estradiol / metabolism
  • Fasting / metabolism
  • Fasting / physiology*
  • Female
  • Follicle Stimulating Hormone / blood
  • Follicle Stimulating Hormone / metabolism
  • Follicular Phase / physiology
  • Humans
  • Hydrocortisone / blood
  • Hydrocortisone / metabolism*
  • Luteal Phase / physiology
  • Luteinizing Hormone / blood
  • Luteinizing Hormone / metabolism*
  • Melatonin / blood
  • Melatonin / metabolism*
  • Ovulation / physiology
  • Progesterone / blood
  • Progesterone / metabolism
  • Thyronines / blood
  • Thyronines / metabolism


  • Thyronines
  • Progesterone
  • Estradiol
  • Luteinizing Hormone
  • Follicle Stimulating Hormone
  • Melatonin
  • 3-Hydroxybutyric Acid
  • Hydrocortisone