Obesity increases the risk of developing endometrial cancer
Endometrial cancer is a type of cancer that develops in the endometrium, which is the lining of the uterus or the womb in the female body. (1) It is the most common type of cancer in the uterus and although scientists and doctors do not know the exact cause of this severe disease, it’s thought that estrogen levels have a very big role in the development of the lining of the uterus, and that increased levels of estrogen may play a role in the development of endometrial cancer. (2) It is also further thought that obesity and endogenous hormones are intricately related and their relationship may provide answers for the explanation of endometrial cancer. (3) Over 40% of incidences of endometrial cancer can be attributed to excess body weight (4) and it has also been shown that endometrial cancer is only prevalent in highly developed countries where obesity and general overweight conditions are endemic. (5)
The same study, conducted by comparing data collected about incidence rates of endometrial cancer in Western, industrialized countries compared to rural Asian or African countries, showed that cancer rates in the endometrium are heavily affected by industrial development or migration from low-risk to high-risk areas. The study clearly showed also that endometrial cancer has a highly environmental, specifically non-genetic risk factors, which are highly related to the lifestyle conducted by females of Western nations. Contributing factors are a low level of physical activity and obesity. (6) (7) The study and many others before it clearly showed that in both pre- and postmenopausal women, endometrial cancer has been related to obesity. Additionally, the risk of endometrial cancer rises approximately linearly with increasing Body Mass Index (BMI). (8) Shockingly, there is even a specific ‘threshold effect’ related to the development of endometrial cancer. Women who hit a BMI of 30kg/m2 or higher are the ones who trigger the risks of endometrial cancer and this effect can even apply to young, premenopausal women.
Endogenous hormones are the culprit
Endogenous hormones seem to play a crucial role in the development of cancer of the endometrial lining. (9) Additionally, the research shows that there is a relationship between the exposure to estrogens at premenopausal levels and the risks of endometrial cancer, which are significant when it comes to the prevalent use of oral contraception as well as postmenopausal therapy. (10) Exposure to estrogens, progesterone, androgens, SHBG, and insulin have all been related to the risks of developing endometrial cancer. (11)
The mechanisms in detail
It is known that the ovaries create and release estrogen. (12) The other side of this is, and this factor is directly related to obesity, is that fat tissues also convert some hormone into estrogen. While it has been shown that normal levels of fat on the body are actually part of an as-yet not-much-talked about organ that regulates and controls certain hormones in the body, an excess of fat-tissue, especially visceral fat in the abdominal area, can have extremely unbalancing effects on the hormone levels and hormone regulation ability of the body.
Excess fat can continually increase your appetite
There is an interesting link between obesity and cancer in respects to a fat hormone known as leptin which has been shown in the laboratory to be able to “enhance the growth of […] cancer cells.” (13) Leptin is released by fat cells and by increasing your body-fat content in this way, there is a higher chance that there will be greater levels of leptin in your blood stream. Leptin is also known as a metabolism regulator, by directly affecting your body-weight and energy expenditure. (14) What leptin does on a molecular level in the body is to suppress and lower appetite. (15) Obese people have been observed to have extremely high levels of leptin circulating in their blood and at first this may seem surprising: if there are high levels of leptin one would think that this has a positive effect on appetite. But the opposite is actually true. If your body has leptin levels that have reached a certain threshold, then you are actually immune to their appetite-suppression effects due to desensitization. (16) The opposite now occurs: the body goes into a spiral of high appetite and constant accumulation of visceral body-fat that keeps the unhealthy cycle going.
Other significant factors
There are certain other significant factors that contribute to the risk of developing endometrial cancer and increased estrogen levels. Many of these are related directly to fertility and pregnancy, for instance, a case-control study in Los Angeles County, California, of 127 endometrial cancer cases aged 45 or younger found that the use of sequential oral contraceptives (SOCs) or estrogen replacement therapy (ERT) has a direct influence on the risk of endometrial cancer. (17) Furthermore, this study also determined that the weight of the women and the number of live births they had in conjunction with contraceptive use all related to the development of endometrial cancer.
Side-effects of the drug tamoxifen (Nolvadex, Tamosin, Tamofen, Tamoxen), which are prescribed and administered for breast cancer treatment are also known to increase the risk of endometrial cancer. (18) Polycistic ovarian syndrome, (19) taking estrogen replacement therapy without progesterone, (20) and menstruation related conditions (21) are also related to the risks of endometrial cancer. In particular, girls who start their menstruation at age 12 or less (usually due to imbalances created by hormones) and women undergoing menopause are also high-risk subjects for endometrial cancer. When obesity is factored into this, then the chance of developing this debilitating disease raises significantly. (22)
Since the risks of developing endometrial cancer are so highly correlated to obesity, because of the epidemic of obesity in Western, developed nations, significantly reducing BMI is a very effective way to combat endometrial cancer. Regular and frequent exercise, altering diet to include more healthy food options and awareness of all the contributing factors to endometrial cancer is the best route to fighting this disease.