There is a direct link between anovulation (absence of ovulation) and obesity and those women who are.
Body fat cells, called adipocytes produce oestrogen. Obese women may have too much oestrogen due to too much body fat.
Women who are underweight may also have anovulation due to lack of body fat.
There may not be enough oestrogen or adequate cholesterol levels being maintained to support the menstrual cycle.
Studies have shown that women with extreme exercise habits have significantly lower levels of estradiol due to low levels of body fat in key areas of the body, leading to anovulation.
Oestrogen is essential for healthy bone formation, healthy gene expression, maintaining healthy cholesterol levels, and is vital for a healthy menstrual cycle.
Too much oestrogen, or too little in the body may cause the feedback loop to not function properly and the menstrual cycle or ovulation may cease.
Now you can see why it is so important to have adequate amounts of body fat; not too much and not too little!