How Does the Keto Diet Affect Hormones?
The irregular or disappearing periods can be traced to hormone changes. “To have a normal period, you have to have a pulsatile release of hormones from the brain,” Dr. Thoppil says. “Any sort of stressor — weight loss or a lot of exercise — can affect that pulsatile release that has to happen for this normal choreography of hormone release that allows you to have regular menses.” A study published in September 2018 in the Journal of Obesity and Weight Loss Therapy noted that keto caused disruption to women’s hormonal systems.
One of the main hormones in play here is estrogen, which is responsible for regulating the menstrual cycle. As weight drops, so do estrogen levels, says Luiza Petre, MD, a board-certified cardiologist and nutrition expert based in New York City. According to previous research, when participants lost an average of 17 pounds, their levels of the estrogen hormone estrone decreased 5.7 percent and the estrogen hormone estradiol dropped nearly 10 percent. The study authors note that weight loss as a result of calorie restriction and exercise significantly decreased estrogen levels.
Another hormone that seems to mess with period regularity is the gonadotropin-releasing hormone (GnRH). GnRH is the signal for pituitary production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are responsible for stimulating ovarian production of estrogen and progesterone, and therefore ovulation). A small study published in the Journal of Translational Medicine in February 2020 found overweight women with PCOS who followed the keto diet for 12 weeks lost a significant amount of weight and also saw a decrease in the ratio between LH and FSH, which is a healthier balance between the two. Another small study, published in the October 2022 Nutrients involving 25 people with obesity and polycystic ovarian syndrome (PCOS) found the keto diet helped the participants improve their metabolism and ovulatory dysfunction.
Body composition changes (such as those that come with weight loss as a result of the keto diet or another diet) can alter GnRH levels, according to an article published in Endotext in May 2018.
The disruption of GnRH causes reduced estrogen, and these changes can disrupt ovulation and lead to amenorrhea.