The American Cancer Society’s epidemiology research program has conducted studies on different approaches to preventing cancer, including early disease detection by screening and identifying major risk factors that cause cancer.
Although genetic inheritance is the well-known factor that can lead to cancer, non-genetic risk factors can play a significant role in causing the disease. According to the Cancer Prevention and Early Detection Facts and Figures 2013, obesity is the second most common risk factor for cancer, while the use of tobacco products is the leading cause.1
Body mass index (BMI) is a tool used to classify body weight. People are considered overweight if their BMI is between 25 to 29.9 kg/m2; obesity is greater than 30 kg/m2 while extreme obesity is defined as BMI of greater than 40 kg/m2.
Trends of obesity in both children and adults have increased significantly over the past three decades. The national center of health statistic data showed that between the years of 2009 and 2010, 16.9% of children and adolescents, as well as 35.7% of adults in the United States were obese. Childhood obesity has more than doubled in children between the ages 6 and 11, increasing from 7% in 1980 to nearly 18% in 2010. Similarly, the percentage of adolescents 12 to 19 years of age who were obese increased from 5% in 1980 to 18% in 2010. For adults between the ages of 20 and 74, the prevalence of obesity has increased from 15% in 1980 to 36% in 2010.2
Being overweight and obese are associated with increased risk of many types of cancer, including breast cancer, aggressive forms of prostate cancer, multiple myeloma, non-Hodgkin lymphoma, and cancers of liver, cervix, and ovary. People who are obese have high amounts of adipose (fat) tissue. Fat tissue is the building block of estrogen, which contributes to risk for breast and endometrial, as well as other hormone-related cancers. Obese individuals also have increased levels of insulin like-growth factor-1, which may also promote the development of certain types of tumors.3
The link between obesity and cancer is believed to arise from the cytokine production by the adipose tissue. By the natural human defense mechanism, the immune system will produce adipokines and cytokines to target the fat tissue, creating an inflammatory environment that is optimal for tumor cell growth. The cytokine-associated proinflammatory state that facilitates tumor cell motility and invasion through the epithelial-mesenchymal layers enhance the metastatic ability of tumor cells.4
As obesity becomes an epidemic health issue in developed countries, its management plays a vital role in defeating many types of cancers. Lifestyle changes, including proper balance of food intake and exercise, are crucial to obesity management.
The American Cancer Society recommends that adults should have at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity physical activity each week; children and adolescents should exercise at least 1 hour per day, 3 days per week. Sedentary behavior such as sitting and watching television should be limited.
In addition, a healthy diet should be engaged with an emphasis on plant sources such as: whole-grain instead of refined-grain products, brown rice instead of white rice, and limited amount of refined-carbohydrates and high-sugar foods. At least 2.5 cups of fruits and vegetables are recommended every day. Moreover, the consumption of processed meat such as bacon, sausage, luncheon meats, and hot dogs, as well as other meats such as beef, pork, or lamb should be limited. Instead, fish, poultry, or beans are good alternative protein source. 1
The number of individuals who are obese has more than doubled over the past 30 years. People may not be aware of the serious consequences of obesity as a risk factor in developing chronic diseases such as diabetes, heart disease, and cancer. Therefore, maintaining a healthy weight by balanced diet and physical activity is the most effective way to manage obesity and subsequently prevent cancer.
1. Cancer Prevention & Early Detection Facts & Figures 2013. American Cancer Society. 2013. http://www.cancer.org/acs/groups/content/@epidemiologysurveilance/documents/document/acspc-037535.pdf. Accessed May 8, 2013
2. Cancer statistics 2013: A Presentation from the American Cancer Society. Cancer Facts & Figures 2013. American Cancer Society. 2013. http://www.cancer.org/research/cancerfactsfigures/cancerfactsfigures/cancer-facts-figures-2013. Accessed May 9, 2013
3. Obesity and Cancer Risk. National Cancer Institute Factsheet. http://www.cancer.gov/cancertopics/factsheet/Risk/obesity. Accessed May 13, 2013
4. Gilbert CA, Slingerland JM. Cytokines, obesity, and cancer: new insights on mechanisms linking obesity to cancer risk and progression. Annu Rev Med. 2013;64:45-57