Cancer and Overweight and Obesity:
Does a Link Exist?
A study published in the January 22, 2010, issue of Cell showed that obesity acts as a tumor promoter in mice. According to some research, obesity increases the risk of cancer development by 150%. In particular, abdominal fat seems to increase a person’s risk for cancer development.
Obesity leads to a chronic inflammatory state, which seems to spur the development of liver cancer. Anti-inflammatory drugs taken for conditions such as rheumatoid arthritis may reduce the risk of developing liver cancer in people who are already at high risk because of obesity. For liver cancer specifically, obesity appears to increase the risk of development by 450%. The tumor-causing effects resulting because of obesity are linked to two specific inflammatory factors, tumor necrosis factor (TNF) and interleukin-6 ( IL-6), and it is suggested that researchers complete studies on people already taking anti-TNF drugs to prove a human link.
Breast, ovarian, and endometrial cancers
An epidemiological study has proven a link between the development of ovarian cancer and obesity in women who have never taken menopausal hormone therapy. The 5-year survival rate for ovarian cancer is only 37%. Women who have never taken hormone therapy after menopause may have as large as an 80% higher risk of ovarian cancer. However, no link between body weight and ovarian cancer was found in women who have used menopausal hormone therapy. Interestingly, women who have a family history of ovarian cancer did not show the same association between increased body mass and risk of ovarian cancer development. However, obese and nonobese women have similar survival rates from ovarian cancer. Women who gain weight throughout their adult years also have an increased risk for the development of menopausal breast cancer, if they do not take menopausal hormone therapy. Excess estrogen released from fat cells may cause, at least in part, both of these cancers.
According to a study published in the October 22, 2007, issue of Archives of Internal Medicine, women who were normal weight at 18 years of age, but then became either overweight or obese between the ages of 35 and 50, had 1.4 times the risk of developing breast cancer, compared to women who maintained their weight throughout adulthood. Luckily, women who initially gained weight, but then lost it, had a risk equivalent to those women whose weight had remained stable. Unlike ovarian cancer, the survival rates for breast cancer are worse for women who are either overweight or whom gain weight during cancer treatment. Women who were overweight at the time of diagnosis, but had never smoked, were twice as likely to die as women who had a normal body mass index (BMI) and had never smoked.
Obese, white women are the most unlikely of any women to undergo regular mammograms. Possible reasons for this lapse in self-care include:
- Poor self-esteem and body image
- A perceived lack of respect from health care providers
- Unwanted weight-loss advice
Development of endometrial cancer is more common in overweight women and much more common in obese women. In fact, in one study published in the International Journal of Epidemiology in 2005, women with a BMI of more than 29 had three times the risk of endometrial cancer, compared to women with a BMI of 23. Having a history of weight cycling during adulthood also led to an increased risk of endometrial cancer development, while women who sustained a weight loss during adulthood had a decreased risk.
Ethnicity seems to have much to do with the link between prostate cancer and body weight. White and Native Hawaiian men seem to have an increased risk of prostate cancer development if they are overweight during older adulthood. On the other hand, Japanese men may have a lower risk of prostate cancer development if they are overweight during older adulthood. Clinical studies have suggested that men with higher BMI or men who gained weight most rapidly since age 25 were at greater risk of treatment failure or receiving a diagnosis of advanced disease.
Studies to look at distribution of fat and proportion of fat in relation to lean body mass are suggested. However, not all studies show a correlation between BMI and the development of prostate cancer, and many studies have shown that no such link exists. Obesity and weight gain throughout adulthood also seems to decrease the survival rate for men with prostate cancer.
Individuals who are very overweight have an increased risk of getting and dying from colorectal cancer. A hormone, leptin, may cause this link. Leptin is fat derived and is therefore found in higher concentrations in obese individuals. Leptin appears to cause precancerous colon cells to produce a greater amount of a growth factor, which increases the blood supply to these cells, thereby promoting tumor growth and leading to the progression of cancer development.
References and recommended readings
ScienceDaily®. Cancer-obesity link could aid prevention efforts. Available at: http://www.sciencedaily.com/releases/2009/04/090430161240.htm. Accessed February 22, 2012.
ScienceDaily. Excess weight and adult weight gain increase risk of dying from prostate cancer. Available at: http://www.sciencedaily.com/releases/2007/01/070108093843.htm. Accessed February 22, 2012.
ScienceDaily. Obese women play cancer roulette. Available at: http://www.sciencedaily.com/releases/2009/03/090316133440.htm. Accessed February 22, 2012.
Science Daily. Obesity and weight gain associated with poorer breast cancer survival. Available at: http://www.sciencedaily.com/releases/2005/02/050201102436.htm. Accessed February 22, 2012.
ScienceDaily. Obesity linked to elevated risk of ovarian cancer. Available at: http://www.sciencedaily.com/releases/2009/01/090105090841.htm. Accessed February 22, 2012.
ScienceDaily. Obesity ups cancer risk, and here’s how. Available at: http://www.sciencedaily.com/releases/2010/01/100121135713.htm. February 22, 2012.
ScienceDaily. Ovarian cancer: obese and non-obese patients have same overall survival. Available at: http://www.sciencedaily.com/releases/2008/12/081229104706.htm. Accessed February 22, 2012.
ScienceDaily. Weight gain in adulthood associated with prostate cancer risk; patterns differ by ethnicity. Available at: http://www.sciencedaily.com/releases/2009/09/090901132802.htm. Accessed February 22, 2012.
Trentham-Dietz A, Nichols HB, Hampton JM, Newcomb PA. Weight change and risk of endometrial cancer. Int J Epidemiol [serial online]. 2006;35:151-158. Available at: http://ije.oxfordjournals.org/cgi/reprint/35/1/151.pdf. Accessed February 22, 2012.
Review Date 2/12