Media Issue Brief: Obesity & Cancer

July 13, 2018


ASCO’s Policy Issue Briefs provide succinct overviews and relevant data on major policy issues impacting patients with cancer and the physicians who care for them. These briefs are designed to be especially helpful for journalists, offering background information on key issues across health policy today. Access ASCO’s full collection of Policy Issue Briefs.

Issue Overview

Over the past two decades, the prevalence of obesity in the United States has dramatically increased. In 2015 and 2016, nearly 40 percent of U.S. adults were obese.The prevalence of obesity has continued to rise steadily. Between 2007–2008 and 2015–2016, the percentage of adults 20 years of age and older with obesity (a body mass index [BMI] of 30 or more) increased from 33.7% to 39.6%. Those with severe obesity (BMI of 40 or more) rose from 5.7% to 7.7%. While obesity and severe obesity continued to grow among adults in this time period, there were no significant overall changes among youth. From 2015-2016 the obesity rate among children and adolescents was 18.5%.1

The increased prevalence of obesity is concerning given that obesity increases the risk of many non-communicable diseases including cardiovascular disease, diabetes, high blood pressure, stroke, and many cancers. Further, obesity increases the rates of mortality for those with these diseases.2,3 In individuals with cancer, obesity is associated with increased risk of treatment complications, comorbidities, and in some cancers, an increased risk of recurrence and cancer-specific and overall mortality.4,5

ASCO’s recent National Cancer Opinion Survey found that less than a third of Americans (31%) realize that obesity is a risk factor for cancer, even though it is currently the second leading preventable cause of the disease. In fact, a recent comprehensive review conducted by the International Agency for Research in Cancer (IARC) found that obesity was linked to the risk of 13 different cancers, including colon cancer, postmenopausal breast cancer, endometrial cancer, and pancreatic cancer.6


Image: Lauby-Secretan B et al. N Engl J Med 2016;375:794-798.

In addition to the increased risk of developing cancer associated with obesity, individuals who are obese at the time of cancer diagnosis often have a high risk of cancer recurrence and morality. This has been best studied in breast cancer, where a recent analysis of more than 200,000 women with early-stage breast cancer found that women who were obese when they were diagnosed had a 35% higher risk of dying from breast cancer and a 41% higher risk of dying from any cause in the years after cancer diagnosis as compared to women who were of normal body weight when they were diagnosed with breast cancer7. Higher body weight at the time of cancer diagnosis has also been linked to a higher risk of cancer-related mortality in cancers of the colorectum, prostate and endometrium8-10.

As many as 28,000 new cancer diagnoses in men and 72,000 in women were estimated to be attributed to obesity or excess weight in 2012 and contributed to as many as one in five cancer-related deaths. If the current obesity trends continue at the same rate over the next 20 years, it is estimated there could be an additional 500,000 to 627,000 cases of cancer attributed to obesity.9-10 Additionally, obesity disproportionately affects certain ethnic, socioeconomic, and geographic groups — disparities that limit access to healthy food and physical activity and the ability to make healthy choices.11

ASCO Obesity Initiative

In 2014, ASCO began efforts to raise awareness about the relationship between obesity and cancer, providing tools and resources to patients and providers, fostering research in this area, and advocating for evidence-based weight management resources for survivors.

ASCO has developed a variety of materials for both patients and providers that share research and help to foster important conversations on weight management. Additionally, ASCO has published a policy statement on obesity and hosted a multidisciplinary summit focused on future research in this area. The Society will continue to collaborate with groups working on obesity within and outside of the oncology field to learn from their efforts and develop joint research efforts and work together to advocate for the changes needed to combat this epidemic and associated health disparities in the United States.12

For More Information


  1. Hales CM, Fryar CD, Carroll MD, Freedman DS, Ogden CL. Trends in Obesity and Severe Obesity Prevalence in US Youth and Adults by Sex and Age, 2007-2008 to 2015-2016. JAMA. 2018;319(16):1723–1725. doi:10.1001/jama.2018.3060
  2. Kitahara, Cari M., Alan J. Flint, and Amy Berrington de Gonzalez. 2014. "Association Between Class III Obesity (BMI Of 40–59 Kg/M2) And Mortality: A Pooled Analysis Of 20 Prospective Studies". Plos Medicine 11 (7): e1001673. doi:10.1371/journal.pmed.1001673.
  3. Flegal, Katherine M., Brian K. Kit, Heather Orpana, and Barry I. Graubard. 2013. "Association Of All-Cause Mortality With Overweight And Obesity Using Standard Body Mass Index Categories". JAMA 309 (1): 71. doi:10.1001/jama.2012.113905.
  4. Calle, Eugenia E., Carmen Rodriguez, Kimberly Walker-Thurmond, and Michael J. Thun. 2003. "Overweight, Obesity, And Mortality From Cancer In A Prospectively Studied Cohort Of U.S. Adults". New England Journal Of Medicine 348 (17): 1625-1638.
  5. Bergstrom, A, P Pisani, V Tenet, A Wolk, and H-O Adami. 2001. "Overweight As An Avoidable Cause Of Cancer In Europe". International Journal Of Cancer 92 (6): 927-927. doi:10.1002/ijc.1285.
  6. Lauby-Secretan, Béatrice, Chiara Scoccianti, Dana Loomis, Yann Grosse, Franca Bianchini, and Kurt Straif. "Body Fatness and Cancer — Viewpoint of the IARC Working Group." New England Journal of Medicine 375, no. 8 (2016): 794-98. doi:10.1056/nejmsr1606602.
  7. D. S. M. Chan, A. R. Vieira, D. Aune, E. V. Bandera, D. C. Greenwood, A. McTiernan, D. Navarro Rosenblatt, I. Thune, R. Vieira, T. Norat; Body mass index and survival in women with breast cancer—systematic literature review and meta-analysis of 82 follow-up studies, Annals of Oncology, Volume 25, Issue 10, 1 October 2014, Pages 1901–1914,
  8. Doleman, B., K.T. Mills, S. Lim, M.D. Zelhart, and G. Gagliardi. "Association between Body Mass Index and Prognosis of Colorectal Cancer: A Meta-Analysis of Prospective Cohort Studies." Techniques in Coloproctology 20, no. 8 (August 2016): 517-35. doi:
  9. Cao, Y., and J. Ma. "Body Mass Index, Prostate Cancer-Specific Mortality, and Biochemical Recurrence: A Systematic Review and Meta-analysis." Cancer Prevention Research 4, no. 4 (2011): 486-501. doi:10.1158/1940-6207.capr-10-0229.
  10. Secord, Angeles Alvarez, Vic Hasselblad, Vivian E. Von Gruenigen, Paola A. Gehrig, Susan C. Modesitt, Victoria Bae-Jump, and Laura J. Havrilesky. "Body Mass Index and Mortality in Endometrial Cancer: A Systematic Review and Meta-analysis." Gynecologic Oncology 140, no. 1 (2016): 184-90. doi:10.1016/j.ygyno.2015.10.020.
  11. Polednak, Anthony P. 2008. "Estimating The Number Of U.S. Incident Cancers Attributable To Obesity And The Impact On Temporal Trends In Incidence Rates For Obesity-Related Cancers". Cancer Detection And Prevention 32 (3): 190-199. doi:10.1016/j.cdp.2008.08.004.
  12. Wang, Y Claire, Klim McPherson, Tim Marsh, Steven L Gortmaker, and Martin Brown. 2011. "Health And Economic Burden Of The Projected Obesity Trends In The USA And The UK". The Lancet 378 (9793): 815-825. doi:10.1016/s0140-6736(11)60814-3.
  13. National Center for Health Statistics, Department of Health and Human Services,. 2016. National Center For Health Statistics. Health, United States, 2015: With Special Feature On Racial And Ethnic Health Disparities. Hyattsville: U.S. Government.
  14. Ligibel, Jennifer A. and Dana Wollins. 2016. "American Society Of Clinical Oncology Obesity Initiative: Rationale, Progress, And Future Directions." Journal Of Clinical Oncology 34 (35): 4256-4260. doi:10.1200/jco.2016.67.4051.
  15. "Defining Adult Overweight and Obesity." Centers for Disease Control and Prevention. June 16, 2016.