Any changes in normal hormone levels can lead to menstrual dysfunction, especially in athletes. This can be caused by overtraining, stress, dieting and weight loss. Typically, menstrual dysfunction occurs when the amount of energy used by athletes exceeds the amount of energy taken in through nutrition
The women described in op’s post are usually far from severely malnourished. They’re more often than not athletic and strong.
Extra muscle and low body fat do the same thing.
Any changes in normal hormone levels can lead to menstrual dysfunction, especially in athletes. This can be caused by overtraining, stress, dieting and weight loss. Typically, menstrual dysfunction occurs when the amount of energy used by athletes exceeds the amount of energy taken in through nutrition
https://www.nationwidechildrens.org/conditions/sports-medicine-menstrual-dysfunction-in-the-athlete#:~:text=Any changes in normal hormone,energy taken in through nutrition.