Effects of fasting during exercise on menstrual cycle function
Official title: Implications for the Timing of Energy Availability on Menstrual Cycle Function
Run by University of Colorado, Colorado Springs · NCT06471582 · Data updated 2026-11-12
This study tests how exercising on an empty stomach affects hormone levels and menstrual cycles in women who regularly run or cycle.
Quick facts
| Study type | Interventional |
|---|---|
| Ages | 18 Years to 40 Years |
| Sex | Women only |
| Enrollment | 64 (estimated) |
| Sponsor | University of Colorado, Colorado Springs Academic / other |
| Locations | 1 site (Colorado Springs, Colorado) |
| Status | Recruiting |
| Started | August 1, 2024 |
| Main results expected | August 31, 2027 |
| Study ends | August 31, 2027 |
| Registry record updated | May 1, 2026 |
| Trial ID | NCT06471582 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Ideal candidates are active women aged 18-35 who participate in structured running or cycling exercises and have regular menstrual cycles.
✕Probably not a fit
Patients with major menstrual cycle disorders or those currently on hormonal contraceptives may not benefit from this study.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This clinical trial investigates how fasted prolonged exercise impacts reproductive hormones and menstrual cycle length in women who regularly engage in running or cycling. Participants will maintain energy availability while undergoing exercise sessions either fed or fasted, and will monitor their menstrual cycles, hormone levels, and stress. The study aims to provide insights into the relationship between energy availability and menstrual health over a three-month period.
Why it matters
Potential benefit: If successful, this study could help improve menstrual cycle regularity and reproductive health in active women.
How similar studies have gone: While there is limited research specifically on this approach, studies on energy availability and menstrual health suggest potential benefits, indicating this area is worth exploring further.
Who can join: the full rules
Show full inclusion / exclusion criteria
Inclusion Criteria: * participates in structured running or cycling exercise for at least 30 minutes on 3 or more days per week * accustomed to exercising for 90 minutes or more * has regular periods every 21-35 days * have not taken hormonal contraceptives for at least the past 6 months * is not currently or trying to become pregnant or breastfeeding, and has not been pregnant or breastfeeding in the past 12 months * does not currently have a diagnosis of a major menstrual cycle disorder (i.e., amenorrhea, polycystic ovary syndrome \[PCOS\], endometriosis, ovarian cancer, ovarian insufficiency, uterine or endometrial cancer) * does not currently have a metabolic disease (i.e., hypothyroidism, hyperthyroidism, Cushing disease, Addison's disease, diabetes, congenital adrenal hyperplasia) * does not currently have a major cardiovascular or respiratory disease Exclusion Criteria: * miss more than 7 consecutive days of aerobic activity (i.e., running, cycling, cross training) * demonstrate clinical low energy availability as defined as energy availability \<30 kcal/kg fat free mass * report menstrual cycle lengths \<21 or \>35 days in the first 2 months of at-home monitoring * do not demonstrate an anticipated rise in luteinizing hormone and progesterone in the first 2 months of at-home monitoring * begin taking a hormonal contraceptive * become pregnant * are diagnosed with a menstrual cycle disorder (i.e., amenorrhea, polycystic ovary syndrome \[PCOS\], endometriosis, ovarian cancer, ovarian insufficiency, uterine, or endometrial cancer) * are diagnosed with a metabolic disease (i.e., hypothyroidism, hyperthyroidism, Cushing disease, Addison's disease, diabetes) * are diagnosed with a major cardiovascular or respiratory disease * are unable to follow instructions for any of the procedures
Where it's running
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William J. Hybl Sports Medicine and Performance Center
Colorado Springs, Colorado, United States Recruiting
Study contacts
- Study coordinator: Marissa Baranauskas, PhD
- Email: mbaranau@uccs.edu
- Phone: 719-255-4475
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.