In female Sprague Dawley rats undergoing 12 weeks of treadmill endurance training with reduced energy intake, a high-cholesterol diet increases serum estradiol by 124% compared to a low-cholesterol control diet and by 171% compared to exercised rats on a low-cholesterol diet.

When an animal eats less food and exercises a lot, its body produces less of a hormone called leptin. This drop in leptin allows more of an enzyme to become active that turns male hormones into female hormones. At the same time, eating more cholesterol gives the body more raw material to make those female hormones. Together, these two changes cause a big increase in the female hormone estradiol.