Since 2007, the World Cancer Research Fund (WCRF) has linked cancer with body fat. Body Fat is a major contributor to 15 types of cancer. Body fat may be a better risk factor for developing cancer than smoking. The problem, we lack awareness of the link between body fat and cancer. For almost 50 years Americans have been warned about the dangers of smoking, while few know that smoking is second fiddle to body fat at causing cancer.
It’s not just about how much you weigh. Too often the message has been about body weight; this can be misleading for many. Reducing your risk of developing cancer is about lowering body fat. Being overweight or obesity is associated with 20% of all cancer diagnosis in the U.S. The National Center for Health data shows that 71% of adults over 20 are overweight, 38% obese. The American Cancer Society (ACS) states that 30% of cancer deaths in the U.S. annually are diet and exercise related.
The Link Between Body Fat and Cancer
Most people are inaccurate in thinking fat is an inactive tissue. Fat is an active tissue with many pathways toward developing cancerous cells and tissue. Some are specific to a particular type of cancer in a specific area of the body, others types of cancer develop from general pathways. In the type mentioned above, body fat actively encourages cell growth and discourages cell death.
Excess fat increases circulation and concentrations of compounds that are known risk factors through pathways that include hormones, cellular proliferation and immune properties. Excessive adipose tissue creates a condition of hyper inflammatory stress. Hyper inflammation is associated with various chronic conditions like cardiovascular disease, diabetes and arthritis, and cancer.
One good example is the case of estrogen; body fat is the main site of estrogen synthesis after menopause. Elevated estrogen levels increase the hormonally associated risk of developing cancers like breast and endometriosis. Additionally, fat cells produce hyper inflammation resulting in chronic low-grade inflammation which can promote cancer development.
High levels of abdominal fat can increase insulin resistance. The pancreas compensates by producing more insulin (hyperinsulinemia) which raise the risk of cancer. Hyperinsulinemia increases levels of IGF-1 (Insulinlike growth factor-1) which regulates cell proliferation and growth. There could be secondary links; overweight or obese people are a significant risk for gastroesophageal disease and gallstones, increasing their risk for esophageal/stomach cancers and gallbladder cancers.
Fat Factors that Cause Cancer:
Hormones (estrogen, testosterone, progesterone) Adipose tissue is the primary site of estrogen synthesis in post menopausal women. High levels of estrogen are associated with post menopausal breast and endometrial cancers and may impact other cancers. Lower testosterone levels in obese men may influence prostate cell differentiation.
- Growth Factors (IGF-1) Obesity increases levels and bioavailability of growth factors such as Insulin and IGF-1, which can increase cell proliferation, inhibit cell death and may promote the growth of certain cancers such as tumors of the endometrium, kidney and pancreas.
- Adipocytokines or adipokine (Leptin, adiponectin) Leptin promotes cell growth. It’s secreted by fat cells and blood levels are higher in obese people. It’s also an inflammatory factor. Blood levels of adiponectin, which may have antiproliferative effects, are low in obese people.
- Inflammatory Factors (tumor necrosis factor, interleukin-6, C-reactive protein, leptin) Obese people often have chronic low-level inflammation which may contribute to the initiation and progression of cancer and has been associated with increased risk.
- Health Conditions Overweight and obesity raise the risk of conditions such as type 2 diabetes, gastroesophageal reflux disease and gallstones, which are associated with higher cancer risk.
All Fat isn’t the Same
The International Agency for Research on Cancer (IARC) uses the term body fatness as an umbrella term. Body fatness includes BMI and waist circumference both associated with increased risk of cancers. Not all fats are the same; abdominal fat (visceral) is more metabolically active than subcutaneous (under the skin).
Researchers are examining the difference between abdominally central fat versus adipose tissue accumulated throughout the body, thus far the research tends to show a stronger correlation to centrally located fat. In an Iowa Women Health Study; weight, BMI, hip circumference, waist circumference and waist to hip ratio all show significantly positive cancer risk association.
Abdominal fat has been cross sectionally associated with cardiovascular disease and cancer and correlates with small ectopic fat deposits including pericardial and periaortic fat, which surround the cardiovascular system and may exert local toxic effects. Ectopic fat deposits are associated cardiovascular risk factors and heart attacks.
Body Fat Major Contributor 15 Types Cancer
- Blood (Myeloma) A 2011 meta analysis by Wallin and Larsson revealed a 15% and 54% higher risk of multiple myeloma mortality in overweight and obese individuals, respectively. The association seemed particularly high in women who were overweight since early adulthood.
- Brain (Meningioma) Since IGF-1 levels increase with body fatness; this is a prime suspect linking weight gain with this particular type of brain tumor. The hormones estrogen and progesterone also play a role.
- Breast The WCRF estimates that 17% of postmenopausal cancer in the U.S. attributed to body fat. Increased levels of estrogen are strongly associated with postmenopausal breast cancer. In postmenopausal women, the primary site of estrogen synthesis is adipose tissue, an increase in body fat increases breast cancer risk due to the elevation of estrogen. Ironically, body fat seems to protect premenopausal women from breast cancer. Women who experience fewer menstrual cycles per year, longer cycles and irregular cycles are at lower risk.
- Colon and Rectum Body fat and abdominal fat (not related to BMI) are associated more with colon than rectal cancer for both men and women. The WCRF estimates colorectal cancer in U.S. due to body fat at 15%. The higher BMI or waist circumference, the higher the risk of cancer. Adult weight game increase risk for colon but not rectal cancer for both sexes. However, overweight men are at increased risk of colon cancer compared to women.
- Esophagus While reflux increases the risk of Barrett’s esophagus, a precursor to esophageal cancer, there is a link between esophageal adenocarcinoma and obesity without reflux. High waist circumference is associated with increased esophageal adenocarcinoma without an elevated BMI. Estimates by WCRF is 35% related to body fat.
- Gallbladder Obesity raises the risk of gallstones and having gallstones increases gallbladder cancer risk. The WCRF estimates 21% of U.S. incidents due to body fat.
- Kidney (Renal-Cell) Increased insulin levels, hypertension and chronic inflammation all may play a role. The WCRF put estimates at 24% related to body fat.
- Liver Body fatness is associated with developing type 2 diabetes, which raises the risk of liver cancer (hepatocellular carcinoma). Obesity increases the risk for nonalcoholic steatohepatitis (NASH). NASH progresses to cirrhosis, the risk of developing liver cancer increases.
- Ovaries The impact of adipose tissue on hormones and inflammatory factors are all thought to play a role. WCRF only estimate a 5% incidents rate in the U.S. due to body fat. More research is needed determining the etiology of ovarian cancer.
- Endometriosis The WCRF estimates that 50% of endometrial cancer in U.S. attributed to body fat. Body fat plays a greater role than in breast cancer because circulating estrogens has a larger role in endometrial cancer development. Postmenopausal estrogen hormone replacement therapy increases the risk of cancer.
- Pancreas Increasing BMI leads to insulin resistance and type 2 diabetes, which increases pancreatic cancer risk. The WCRF estimates 19% of cases are related to obesity.
- Prostate The lower testosterone levels of obese males may lead to the growth of a less differentiated, more aggressive type of prostate cancer. Consistent evidence shows that greater body fat is related to advanced prostate cancer. Only about 11% according to the WCRF are related to body fat.
- Stomach (Gastric Cardia) 2014 meta analysis concluded that obesity is associated with gastric cancer risk, especially males and both overweight and obese.
- Thyroid Overweightness throughout adulthood is associated with increased incidence of thyroid cancer and higher thyroid cancer mortality. Thyroid grows larger with increasing body mass.
- Uterus increased levels of estrogen are strongly associated with the risk of cancer of the uterine lining (endometrial cancer). Hyperinsulinemia caused by obesity also increases the risk of endometrial cancer and chronic inflammation.
Does Weight Loss Help
The first way to take in this information is to realize that body fat is only a contributing factor. Many factors that are thought to contribute to cancer cell growth may not be more than a contributing factor with other confounding factors playing a significant. There is plenty uncertainty related to the mechanisms that link body fat with this risk of cancer of the rectum, prostate, pancreas, ovary or kidney.
However, the best way to prevent or lessen the risk of developing cancer, where the link is strongly correlated is to avoid accumulating excess body fat or begin to reduce the amount of body fat you are currently carrying around. As we said at the beginning, there are 40% of adults in the U.S. who are categorized as obese. The good news for these people is that weight loss does seem to reduce the risk of cancer. Weight loss reduction has consistently been shown to reduce the risk of cancer or its contributing factors which may lead to cancer.
A small caveat to the research mentioned above showing benefits of weight loss to reduce cancer risk, more longitudinal research trials need to be conducted. The initial results appear promising, but it is not known whether these results will hold over time. If you are overweight, losing weight has consistently shown to improve overall health status.
What to do
Unfortunately, weight loss is not a real possibility, primarily due to socioeconomic levels. Overweight and obesity is a major problem in the U.S. due in large part to excess caloric intake of sugary and fatty foods and a lack of physical activity. Both issues which affect people of lower economic levels more than people of higher means.
Healthcare, unfortunately, is the frienemy to the poor and disadvantaged. Things like nutritious foods, places to exercise, wellness counseling or medical procedure like bariatric surgery are not attainable or difficult to access. Therefore the best option is educating young people about the downside of accumulating excess weight throughout their lives. Additionally, providing education for people about how to lose weight by incorporating physical activity and vegetables into their everyday life to aid in lessening their weight gain potential.
While lifestyle choices are the best and simplest methods towards improving health status, it is also important to recognize lifestyle choices does not carry the same meaning and understanding across the economic railroad tracks. The direr your financial situation, the more immediate your choices in life become. As a society, we may get to embrace the fact that with such a high overweight and obese population that the choices we are making are sacrificing the lives or quality of life for millions of Americans.
Thalheimer, J. C. (2017). CANCER’S Link to BODY FAT. Today’s Dietitian, 19(1), 34-38.
Byers, T., & Sedjo, R. L. (2015). Body fatness as a cause of cancer: epidemiologic clues to biologic mechanisms. Endocrine-Related Cancer, 22(3), R125-R134. doi:10.1530/ERC-14-0580
Geoffrey C., K., Moonseong, H., Jean, W., Catherine, M., Cynthia A., T., Sylvia, W., & Thomas E., R. (2013). Body fat and risk of colorectal cancer among postmenopausal women. Cancer Causes & Control, (6), 1197.
Britton, K. A., Massaro, J. M., Murabito, J. M., Kreger, B. E., Hoffmann, U., & Fox, C. S. (2013). Body fat distribution, incident cardiovascular disease, cancer, and all-cause mortality. Journal Of The American College Of Cardiology (JACC), 62(10), 921-925. doi:10.1016/j.jacc.2013.06.027
Guerrios-Rivera, L., Howard, L., Frank, J., De Hoedt, A., Beverly, D., Grant, D. J., & … Freedland, S. J. (2017). Is Body Mass Index the Best Adiposity Measure for Prostate Cancer Risk? Results From a Veterans Affairs Biopsy Cohort. Urology, 105129-135. doi:10.1016/j.urology.2017.03.042
Kabat, G. C., Xue, X., Kamensky, V., Lane, D., Bea, J. W., Chen, C., & … Rohan, T. E. (2015). Risk of breast, endometrial, colorectal, and renal cancers in postmenopausal women in association with a body shape index and other anthropometric measures. Cancer Causes & Control: CCC, 26(2), 219-229. doi:10.1007/s10552-014-0501-4