Hormonal
Female reproductive ability, including the onset of menarche and the maintenance of regular ovulatory cycles, is dependent on maintaining a critical minimum body weight and a specific body fat percentage (approximately 17% at menarche and 22-28% in adulthood), rather than chronological age alone.
For women, achieving and maintaining a minimum body weight and body fat percentage (roughly 17-22% depending on life stage) is biologically required for regular ovulation and fertility. Significant weight loss (10-15% of body weight) or excessive exercise can halt menstrual cycles, regardless of chronological age. Restoring cycles requires reaching a specific weight-for-height threshold, not just feeling 'healthy'.
Our findings (Frisch & McArthur, 1974) that menarche and the maintenance of regular ovulatory cycles in women are each dependent on the maintenance of a minimum weight for height, apparently representing a critical fat storage, implied that a particular body composition of fat to lean, or fat to body weight, is an important determinant for reproductive ability in the human female.
Why this rating
Based on longitudinal human studies, cross-sectional data, and animal models, though the paper is a review/hypothesis paper rather than a single RCT.
Source
BODY FAT, PUBERTY AND FERTILITY
Rose E. Frisch · Biological reviews/Biological reviews of the Cambridge Philosophical Society · 1984
DOI 10.1111/j.1469-185x.1984.tb00406.x
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- Intense physical exercise combined with low energy intake (common in ballet dancers and athletes) delays menarche and causes amenorrhea by preventing the attainment of the critical lean mass-to-fat ratio required for reproductive function.Good
- Adipose tissue serves as a significant extra-gonadal source of estrogen through the conversion of androgens, meaning that body fatness directly influences the quantity and potency of circulating estrogen and thus reproductive ability.Good
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