Roughly 10% of women in their reproductive years experience endometriosis, a condition where endometrial cells migrate out of the uterus and into surrounding tissues causing issues like pelvic pain, menstrual irregularities, and infertility.
Many factors have been proposed as a link to the development of this condition, including age at menarche and lower parity. But a new study suggests that a complex relationship between fat tissue metabolism could play a larger role than anyone realized.
The study, published in Obstetrics & Gynecology Science, sought to explore the relationship between the amount and distribution of adipose tissue and the development of endometriosis.
This isn’t a simple question of body weight, though, but more a look at where fat is stored and how the biochemical secreted by this tissue may help or hinder the development of endometriosis.
The study team examined epidemiological and population studies on risk factors for endometriosis, noting that a lot of research has pointed to an inverse relationship between body-mass index and the risk of developing this condition.
These studies found that women with lower BMI and less obesity had higher rates of endometriosis, with one suggesting a 33% reduction in endometriosis risk for every 5 kg/m2 increase in BMI. The study authors suggest, however, that higher BMI women may be less likely offered surgical intervention for pelvic pain, therefore lowering the chances that endometriosis be diagnosed laparoscopically.
There were also some studies that linked increased body size to endometriosis, just not necessarily at the time of diagnosis. One study found that being overweight around the ages of 10 to 16 years old was associated with a higher rate of endometriosis, suggesting that teenage insulin resistance and hyperinsulinemia, and the hormone changes these trigger may play a role in later development of endometriosis.
Other studies questioned whether lower BMI rates associated with endometriosis were a factor in pathogenesis, considering that the abdominal pain and emotional stress that come with endometriosis might cause weight loss after the condition has manifested.
The study authors, however, were particularly interested in learning how somatotype and body fat distribution played a role in endometriosis development, noting an inverse correlation in women—but only before age 30.
Women with more peripheral body fat—which stores higher levels of estrogen—were more likely to develop endometriosis, according to the report. Similarly, lean women with lower amount of fat tissue, particularly below the waist, were more likely to develop the condition. Since endometriosis is an estrogen-dependent condition, the study authors suggest that it is estrogen that influences the amount and locations of fat tissue.
Age-related changes in body fat matter, too, the report suggests. One study found an association between obesity and the severity of endometriosis, explaining that the growth of endometrial lesions may be impacted by gradual changes in body fat that occur naturally with aging. This is illustrated by the fact that while lean women have higher rates of endometriosis, some studies have found that obesity is linked with more advanced stages of the disease.
It’s not just fat tissue itself that plays a role in this disease, either. The study authors suggest that adipocytokine—a cytokine secreted by fat cells—might play a role in the establishment or progression of endometriosis. The proximity of visceral fat to the organs in the pelvic cavity where endometriosis forms could explain the underlying biological connection. Adiponectin is another type of these cytokines that could actually act as an anti-endometriotic substance thanks to its anti-inflammatory and anti-angiogenic properties. Levels of adiponectin were notably lower in women with endometriosis, according to the report.
Genetics and inflammation undoubtedly play a role in the development of both obesity and endometriosis, but the study team concluded that better studies are needed to really understand the role different biochemical can have, as well.