The purpose of the present study is to characterize the endocrine and metabolic responses to a modest, short-term energy deficiency (\~250 kcal/day) across the menstrual cycle in recreationally active women using different contraceptive methods (oral contraceptive, hormonal IUD, and non-hormonal IUD). This study will leverage daily urinary hormone metabolite tracking and comprehensive metabolic assessments, providing foundational data addressing an important and previously unexamined interaction between energy availability and hormonal regulation in contraceptive users.
The purpose of the present study is to characterize the endocrine and metabolic responses to a modest, short-term energy deficiency (\~250 kcal/day) across the menstrual cycle in recreationally active women using different contraceptive methods. The investigators will be focusing on oral contraceptive users, hormonal IUD, and non-hormonal (i.e., copper IUD). Daily urinary hormone metabolite tracking and comprehensive metabolic assessments (i.e., resting metabolic rate, body composition via DXA, exercise logs, and energy intake) will be used to provide foundational data addressing an important and previously unexamined interaction between energy availability and hormonal regulation in contraceptive users. Based on evidence that female reproductive hormones are sensitive to energetic stress, that estrogen plays a central role in regulating metabolism and endocrine function, and that hormonal contraceptive methods differentially alter endogenous hormone profiles, the central hypothesis of this study is that a modest, controlled energy deficiency (\~250 kcal/day) will alter reproductive hormone profiles across the menstrual cycle in recreationally active women using contraceptives. Specifically, it is hypothesized that changes in urinary reproductive hormone measures will be detectable during an energy-deficient cycle compared to a baseline cycle, and that the magnitude and pattern of these changes will differ by contraceptive type, with hormonal oral contraceptive users demonstrating a different hormonal response to energy deficiency than copper or hormonal intrauterine device users. A secondary hypothesis is that energy deficiency-induced hormonal changes will be associated with alterations in resting metabolic rate and body composition, and that these associations may be moderated by exercise energy expenditure and perceived stress. Collectively, these hypotheses are grounded in prior research demonstrating hormonal sensitivity to energetic perturbations and the distinct endocrine environments created by different contraceptive methods, while addressing a clear gap in the current literature regarding the interaction between energy availability and hormonal regulation in contraceptive users.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
SCREENING
Masking
NONE
Enrollment
30
Following an initial baseline menstrual cycle, participants will be subjected to at least two weeks of a \~250 kcal/day energy deficit monitored through daily diet tracking.
University of Southern California Health Sciences Campus Center for Health Professions
Los Angeles, California, United States
Urinary hormone exposure
Participants will be asked to track daily urine concentrations of estrogen and progesterone throughout a baseline (i.e., non-energy-deficient state) menstrual cycle and a menstrual cycle with an imposed energy deficit. The outcome will compare hormone exposure measured by the urinary concentrations between the two cycles.
Time frame: From enrollment to energy deficit menstrual cycle is 3 months/90 days
Estimated versus actual resting metabolic rate
Body composition and estimated metabolic rate will be collected using DXA. The DXA will be measured at baseline and at the conclusion of the energy-deficient menstrual cycle. Resting metabolic rate will be measured via indirect calorimetry testing at baseline, at the beginning of the second monitored (i.e., energy-deficient) menstrual cycle, and at the conclusion of the energy-deficient menstrual cycle. The estimated and actual metabolic rate will be compared as an assessment of energy status. Participants will also be asked to track exercise using a paper log or wearable device to estimate exercise energy expenditure (EEE), and daily intake (EI) will be measured via a paper log or an application. These values will be subtracted (EI-EEE) and normalized to fat-free mass collected via DXA to estimate energy availability.
Time frame: From enrollment to completion 90 days/3 months
Eating behaviors and attitudes will be measured using the EDEQ and the Three Factor Eating Questionnaire
The Eating Disorder Examination Questionnaire is a 12 item questionnaire scaled from 0 to 3 (0 being 0 days and 3 being 6 to 7 days) assessing feelings around eating behaviors, body image, and restraint. The Three Factor Eating questionnaire is an 18-question survey that assesses cognitive restraint, emotional eating, and uncontrolled eating on a 4 point Likert scale (0 being never and 3 being at least once a week).
Time frame: From enrollment to conclusion 90 days/3 months
Subjective stress levels will measured using the Perceived Stress Scale
The Subjective Stress Scale measures percieved stress through 10 questions about recent stress perceptions on a 0 to 4 Likert scale (0 being never; and 4 being very often).
Time frame: From enrollment to conclusion 90 days/3 months
Low Energy Availability Indicators will be assessed using the LEAF-Q
The low energy availability in Females Questionnaire (LEAF-Q) is used to identify female athletes 'at risk' of low energy availability. This questionnaire assesses physiological symptoms associated with LEA, including 25 questions arranged into 3 sections; eating and reproductive assessment, injury assessment, and gastrointestinal symptom assessment. A total score of ≥8 out of 25 questions indicates that the athlete is at risk of LEA. There is a standardized scoring system that varies by question and subquestion.
Time frame: From enrollment to conclusion 90 days/3 months
Body composition will be measured using DXA
Dual-energy x-ray absorbtometry will be used to assess body composition including segmental analysis of body fat and lean mass.
Time frame: From enrollment to conclusion 90 days/3 months
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