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The Link Between Obesity and Cancer Risk

obesity link to cancer risk

Why is this an important topic for life underwriters?

While it is well known that obesity is a common risk factor for Diabetes or Pre-Diabetes/Impaired Glucose Tolerance, it is important for life underwriters to understand that higher BMI could possibly increase the risk of certain cancers.

Before demonstrating the link between obesity and cancer, let’s start with the basics of obesity.

What is Obesity?

Obesity is a condition in which a person has an unhealthy amount and/or distribution of fat. This is measured by an individual’s Body Mass Index (BMI) which is calculated by dividing a person’s weight in kilograms by their height, in meters, squared (kg/m2). The BMI is a more accurate measure of obesity than weight alone.  Along with the BMI, measurements that reflect the distribution of fat are also indicators of obesity and disease risks. For example, waist measurement and waist-to-hip ratio (waist circumference divided by the hip circumference).

Obesity rates in Canada

Approximately one in four Canadians are obese; of which 8.6% are between the ages of six and seventeen. The obesity rates vary vastly across Canada, from 5.3% in Richmond, BC, to 35.9% in Mamawetan/Keewatin/Athabasca region of Saskatchewan.  Factors that influence obesity include physical activity, diet, socioeconomic status, ethnicity, immigration and environmental factors.

Obesity is on its way to replacing tobacco as the number one preventable cause of cancer

It is estimated that obesity contributes to as many as 1 in 5 cancer-related deaths. In 2007, more than 84,000 new cancer cases were due to obesity. Although the percentage of cancer cases attributed to obesity does vary, it is as high as 40% for some cancers, particularly esophageal and endometrial.

What is the link between obesity and cancer?

  • Increased blood levels of insulin: obese people often have increased blood levels of insulin and insulin-like growth factor-1 (IGF-1). This condition, known as hyperinsulinemia or insulin resistance, precedes the development of type 2 diabetes.  High levels of insulin and IGF-1 may promote the development of colon, kidney, prostate and endometrial cancers.
  • Chronic local inflammation: obese or overweight people are more likely to have conditions or disorders that are linked to, or that cause, chronic local inflammation. This inflammation, can, over time, cause DNA damage that leads to cancer. This chronic low-level or “subacute” inflammation is a risk factor for certain cancers.  For example: obesity is a risk factor for gallstones (characterized by chronic gallbladder inflammation). Gallstones and a history of chronic gallbladder inflammation is a strong risk factor for gallbladder cancer. GERD (gastroesophageal reflux) or Barrett’s esophagus, is a likely cause of esophageal adenocarcinoma. Chronic ulcerative colitis and hepatitis are also risk factors for different types of liver cancer. 
  • Higher amounts of estrogen: fat tissue (a.k.a adipose tissue) produces higher amounts of estrogen. These high levels have been linked to the increased risk of estrogen-sensitive breast cancers, endometrial, ovarian and some other cancers.
  • Cell growth regulators: fat cells (a.k.a adipocytes) may also have direct or indirect effects on other cell growth regulators. Fat cells produce adipokines, which are hormones that may stimulate or inhibit cell growth. For example; Leptin promotes cell growth, whereas Adiponectin may have anti-proliferative effects.

Evidence shows that higher amounts of body fat are associated with increased risks of certain cancers.

This includes:

  • Esophageal adenocarcinoma: overweight people are twice as likely, compared to normal-weight people, to develop esophageal adenocarcinoma. People that are extremely obese are more than four times as likely.
  • Endometrial cancer: Obese and overweight women are 2 to 4 times as likely to develop endometrial cancer (cancer of the lining of the uterus). Extremely obese women are about 7 times as likely. The risk of endometrial cancer increases with increasing weight gain in adulthood, especially in those women who have never used menopausal hormone therapy.
  • Liver Cancer: Overweight individuals are up to twice as likely to develop liver cancer. The link between obesity and liver cancer is stronger in men than women.
  • Gastric cardia cancer: Obese people are nearly twice as likely as normal-weight people to develop cancer in the upper part of the stomach, the part that is closest to the esophagus.
  • Kidney Cancer: People who are obese are nearly twice as likely to develop renal cell cancer (the most common type of kidney cancer). Although high blood pressure is a known associated risk for kidney cancer, obesity is an independent risk factor for kidney cancer.
  • Multiple Myeloma: There is a 10-20% increased risk of developing multiple myeloma in overweight or obese individuals.
  • Meningioma (slow-growing brain tumor that arises in the membranes surrounding the brain and spinal cord): there is approximately a 20% increase in overweight individuals and a 50% increase in those that are obese.
  • Pancreatic Cancer: Those individuals that are overweight or obese are 1.5 x as likely to develop pancreatic cancer.
  • Colorectal cancer: There is a slight increase in the risk of developing colorectal cancer (30%) compared to those people at a normal weight. The increased risks of colon and rectal cancers are seen in both men and women, although the increases are higher in men.
  • Thyroid Cancer: There is only a slight increase in the risk of developing thyroid cancer (10%) in people that are obese or overweight.
  • Gallbladder Cancer: People that are overweight have approximately a 20% increase risk of gallbladder cancer. However, those individuals that are obese have a 60% increase risk of gallbladder cancer. The risk is greater in women than men.
  • Breast Cancer: Among post-menopausal women with a higher BMI, there is a 20-40% increase risk of developing breast cancer. Obesity is also a risk factor for men for developing breast cancer.

Sources: National Cancer Institute, The New England Journal of Medicine

What life underwriters need to know when reviewing applicants with a history of obesity

As life underwriters, not only do we need to be aware of the risk of CAD and diabetes, but also of the strong association between increased BMI/overweight/obesity and cancer risks.  Whether you are underwriting Life insurance, Critical Illness insurance or Disability insurance, information about obesity with the increased cancer risk is something that should absolutely be filed away for future use.

What is the effect of weight loss on cancer risk?

There still needs to be further research and studies done to understand the effects that weight loss may have on this risk.  Will there be a decrease in the risk of cancer? How would eating healthier, or eating certain food affect the outcome?  How does obesity effect the survival rate of the cancers?  While there are many questions yet to be answered it is apparent a link between obesity and cancer exists and is indeed something life underwriters need to be familiar with.


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Written by: Karen McLeod

Karen McLeod is the Director of Underwriting Services at RGAX. She is responsible for managing a team of life underwriters and providing superior service to current and prospective clients. In addition to fifteen years’ experience in the insurance industry, she has extensive experience in life, critical illness, and disability insurance and in structured settlements, life valuations, and providing invaluable coaching to underwriters of all levels. Karen holds FALU and FLMI designations and is currently the Assistant Director for the CIU’s program committee.