Research

Hormonal

Female reproductive function (menarche and ovulatory cycles) requires a critical minimum body fat percentage (approximately 17% for menarche onset and 22% for cycle maintenance), below which hypothalamic dysfunction causes amenorrhea.

If you are female and experiencing irregular periods or amenorrhea, check your body fat percentage, not just your weight. If your body fat drops below ~17-22%, your reproductive system may shut down. To restore cycles, you likely need to gain fat or reduce exercise intensity, even if your total body weight remains the same.

GoodSupportsHIGH confidence
Evidence is presented in support of the hypothesis that a particular, minimum ratio of fat to lean mass is normally necessary for menarche (~17% fat/body wt) and the maintenance of female reproductive ability (~22% fat/body wt).
Rose E. Frisch · Human Reproduction · 1987

Why this rating

Based on longitudinal cohort studies and clinical observations of athletes and anorectic patients, though primarily observational/correlational.

Source

Body fat, menarche, fitness and fertility

Rose E. Frisch · Human Reproduction · 1987

DOI 10.1093/oxfordjournals.humrep.a136582

narrative_review · n=5388Cited 376×
Read the paper
DOI resolved against Crossref · corpus check 2026-06-10

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