Nutrition and Menstrual Cycles Study (CaREFREE Study: Calorie Restriction, Environment, and Fitness: Reproductive Effects Evaluation) | National Institute of Environmental Health Sciences
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Nutrition and Menstrual Cycles Study (CaREFREE Study: Calorie Restriction, Environment, and Fitness: Reproductive Effects Evaluation)
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Study Background
This study is no longer accepting participants.
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Many women develop irregular menstrual cycles which may make it difficult to become pregnant and increase the risk of osteoporosis. Why do exercise and diet have this effect in some women but not others? This study will help us understand how nutrition, exercise, and the environment affect women's reproductive cycles.
Participants will track three consecutive menstrual cycles and come in for 9-10 visits on specific days. Participants will undergo two 5-day exercise and diet regimens provided by the study. Procedures include a physical exam, fitness testing, measurement of body fat and bone density, blood sampling, and daily at home blood & urine tests.
Eligibility Criteria
This study is no longer recruiting participants
Study participants: women, 18–28 years old
Reported menarche between the ages of 11–14 years
A history of self-reported regular menstrual cycles when not on contraceptive medication of between 25 and 35 days (inclusive) at prescreen and knowledge of date of onset of menses before the screening visit
A BMI of 18.5 to 27 kg (Summation)m(2) and a weight >= 93 lbs.
Agrees to use barrier contraception method for the duration of the study
Agrees to abstain from alcohol consumption during both 5-day diet/exercise study interventions
Agrees to abstain from donating blood during the study and within 30 days of completing the study
Principal Investigator
Natalie D. Shaw, M.D., MMSc.
Senior Investigator
Tel 984-287-3716
[email protected]
Abbie Smith-Ryan, Ph.D.
Associate Researcher
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Last Reviewed: December 30, 2025