Bariatric surgery affects a woman's menstrual cycle by helping them lose a significant amount of weight and better regulate their hormones and bodily functions. Studies have found that bariatric surgery is the most effective method of treating irregular periods in obese women resulting in a 35% decrease in irregular menstrual cycles.  

Bariatric Surgery Affects a Woman's Menstrual Cycle

But how exactly does bariatric surgery affect a woman's menstrual cycle? 

We know that obesity causes many medical conditions and, in particular, is linked to causing hormonal imbalances. This explains why bariatric surgery is also called metabolic surgery as it has an impact on hormones such as ghrelin, leptin, insulin, thyroid, and the sex hormones estrogen and progesterone. 

How Hormonal Imbalances Affect a Woman's Menstrual Cycle

Traditionally, the imbalance of sex hormones is more common in women than men. Typically, we will see patients with elevated testosterone levels and low estrogen levels, leading to polycystic ovarian syndrome (PCOS). Yet we see some women with higher estrogen levels than the hormone progesterone. 

Hyperestrogenism, characterized by high amounts of estrogen in the body, has been linked to excess weight. When a woman has too much estrogen, she may experience period-like symptoms such as bloating, swollen breasts, and mood swings, yet she won't have a menstrual cycle. 

Sex hormones are heavily influenced by obesity and fat distribution. Bariatric surgery affects a woman's menstrual cycle by helping to regulate these hormones and maintain regular periods. In one study of 515 women who had undergone bariatric surgery, 38.6% of women reported irregular periods before weight loss surgery, and 25% claimed to have irregular periods after bariatric surgery.

How Anovulation Affects a Woman's Menstrual Cycle

Anovulation is a common symptom in obese women of childbearing years. Anovulation is when the woman's egg does not release from the ovary during the menstrual period. This can cause irregular, sporadic, or absent menstrual cycles. 

Studies have shown that even a moderate reduction in weight by 5% can "reverse obesity-related anovulation." A group of 98 women who had reported anovulation symptoms pre-operatively saw a 71.4% improvement in their menstrual cycles after bariatric surgery. And the women who went back to having regular ovulation cycles saw a more significant reduction in their weight, likely due to the improved regulation of the sex hormones. 

The Impact on Fertility

When a woman experiences irregular menstrual cycles, she is at a greater risk of developing fertility issues, which explains why PCOS is a significant concern for obese women of childbearing age. 

Polycystic Ovarian Syndrome (PCOS) is a hormonal imbalance that affects 6 to 12% of American women of childbearing age. This common disorder causes the ovaries to enlarge with numerous fluid-filled cysts (follicles) that do not regularly release with ovulation. 

The consequences of developing PCOS include infertility, obesity, and metabolic syndrome (diabetes, sleep apnea, high cholesterol). Even though there is no cure for PCOS, bariatric surgery has shown to be the most effective and durable tool for PCOS patients.

The incidence of PCOS decreased from 45.6% to 6.8%, and infertility decreased from 18.2% to 4.3% in PCOS patients who had undergone bariatric surgery. Studies have also shown that women with a history of PCOS who underwent bariatric surgery and achieved successful weight loss had fewer pregnancy complications than women with PCOS who did not undergo bariatric surgery.

"Even a modest reduction in your weight — for example, losing 5 percent of your body weight — might improve your condition. Losing weight may also increase the effectiveness of medications your doctor recommends for PCOS and can help with infertility." – Mayo Clinic

Conclusion

Bariatric surgery affects a woman's menstrual cycle by improving the regulation of the sex hormones, particularly estrogen, and increasing ovulation incidences. Women are likely to experience regular periods, shortened periods, and improve their fertility in childbearing years through a significant reduction in weight after bariatric surgery.