Are menstrual disturbances associated with an energy availability threshold? A critical review of the evidence.
Level 5 - mechanism / opinion, no new human data
Narrative critical review synthesizing mechanism and trial data without systematic review methodology
PubMed 38194640 · doi:10.1139/apnm-2023-0418
What was done
This critical review evaluated physiological and clinical evidence examining whether disruptions to the reproductive axis and menstrual disturbances occur below an energy availability (EA) threshold of 30 kcal/kg lean body mass (LBM) or fat-free mass (FFM) per day. The authors evaluated findings from short-term laboratory studies (4–5 days of induced low EA in sedentary, regularly menstruating women) and longer randomized intervention trials (2–3 menstrual cycles) evaluating ovarian and menstrual outcomes.
What was found
Short-term studies of EA < 30 kcal/kg LBM/day demonstrated decreased serum triiodothyronine (T3), decreased luteinizing hormone (LH) pulse frequency, and increased LH pulse amplitude. In longer trials, weight loss (-4 ± 0.3 kg over 2 cycles) induced luteal phase defects, delayed menses, and anovulation. A 3-cycle trial found that 57% of women developed luteal phase defects, anovulation, and/or oligomenorrhea, and EA < 30 kcal/kg FFM/day increased the risk of menstrual disturbance by 50%. However, menstrual disturbances occurred both above and below 30 kcal/kg/day, and LH pulse frequency changes predicted only luteal phase defects, not oligomenorrhea or anovulation.
Why it matters
This review clarifies that 30 kcal/kg/day is not an absolute threshold below which menstrual disturbances abruptly occur, but rather represents a zone of elevated risk along a continuum.
Limits
The paper is a narrative critical review rather than a systematic review or meta-analysis. Long-term experimental data in humans are limited to very few trials, and acute changes in LH pulsatility did not consistently predict major clinical outcomes like anovulation.
Cited by
- supports Chronic or prolonged fasting and severe calorie restriction can suppress ovulation and cause the cessation of the menstrual cycle in women.