How Being Overweight Can Increase Cancer Risk

By Colin E. Champ, MD, CSCS – Radiation Oncologist

The correlation between cancer risk and obesity is clear, what causes this increased risk is less clear.

To understand how obesity can increase cancer risk, one must understand obesity. What is obesity? Simply stated, obesity is a disease in which a person has an unhealthy amount and/or distribution of body fat. (Obesity and Cancer, 2022) Body Mass Index is most commonly used to determine if someone is obese. BMI is calculated by dividing a person’s weight (in kilograms) by their squared height (in meters). This method provides a more accurate record of obesity than weight alone. Most American adults weigh more than recommended. Being obese or overweight puts these people at a much higher risk for various cancers. (Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States, 2017)

Obesity places a person at a greater risk of at least 13 types of cancer and an elevated risk of death from all causes. (Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States, 2017) Research shows that it is primarily due to increased inflammation caused by visceral fat -the fat that surrounds your vital organs. (How Does Obesity Cause Cancer, 2017) Excess fat affects processes in your body. Obesity affects processes like how your body manages hormones like estrogen and insulin that can lead to increased cancer risk by affecting when and how cells divide and die. The correlation between being overweight or obese and cancer risk is complex. The risk also varies based on the specific cancer type, but altogether is believed to be associated with increased insulin and hormone levels and chronic inflammation.

How can obesity increase the risk of cancer?
“Cancer happens when cells reproduce uncontrollably, damaging the cells around them and causing illness. The more cells divide and reproduce, the higher the risk that something will go wrong and a tumor will form.” (Obesity and Cancer, 2022) Adipose tissue (fat tissue) produces high amounts of estrogen. Increased estrogen levels have been associated with an increased risk of breast, endometrial, ovarian, and other cancers. Chronic inflammatory conditions are often found in people with obesity. Conditions like gallstones or non-alcoholic fatty liver disease can lead to DNA changes. These conditions increase the risk of biliary tract and other cancers.

Increased insulin levels are due to insulin resistance and precede the development of type 2 diabetes. High insulin levels promote the growth and development of colon, kidney, prostate, and endometrial cancers. (Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States, 2017)

“The link between overweight/obesity and cancer risk is complex and varies with the specific type of cancer, but is thought to involve increased insulin and hormone levels, and chronic inflammation. While some overweight/obesity-related cancers, such as breast cancer, colorectal cancer, and kidney cancer are common, others are relatively rare. The extent to which being overweight or obese increases the risk of cancer also varies with cancer site.” (Overweight/Obesity-Associated Cancers, 2021)

Statistics from 2005 2014 regarding cancer types associated with overweight and obesity:
• Of cancers linked to being overweight and obese, fifty-five percent are diagnosed in women and 24 percent of those diagnosed in men.
• Of cancers linked to being overweight and obese, Black males and American Indian/Alaska Native males had higher incidence rates than white males.
• Of cancers linked to being overweight and obese, higher incidence rates were found among non- Hispanic blacks and non-Hispanic whites compared with other racial and ethnic groups.
• Cancers associated with overweight and obesity increased by 7 percent, not including colorectal cancer. During that same time there was a decrease of 13 percent in cancers not associated with overweight and obesity. There was also a 23 percent decrease in colorectal cancer, due in large part to screening.
• Cancers associated with overweight and obesity increased among 18 to 75 year-olds, not including colorectal cancer, (Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States, 2017)

Cancer and Obesity – What can you do?
Not all cases of the cancers mentioned above can be attributed to obesity or being overweight. However, excess body weight is a modifiable risk factor. What does that mean? It means that there are steps that a person can take to prevent obesity and decrease their risk of some types of cancer.

Increased insulin levels are due to insulin resistance and precede the development of type 2 diabetes. High insulin levels promote the growth and development of colon, kidney, prostate, and endometrial cancers. (Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States, 2017)

“The link between overweight/obesity and cancer risk is complex and varies with the specific type of cancer, but is thought to involve increased insulin and hormone levels, and chronic inflammation. While some overweight/obesity-related cancers, such as breast cancer, colorectal cancer, and kidney cancer are common, others are relatively rare. The extent to which being overweight or obese increases the risk of cancer also varies with cancer site.” (Overweight/Obesity-Associated Cancers, 2021)

Statistics from 2005 2014 regarding cancer types associated with overweight and obesity:
• Of cancers linked to being overweight and obese, fifty-five percent are diagnosed in women and 24 percent of those diagnosed in men.
• Of cancers linked to being overweight and obese, Black males and American Indian/Alaska Nativemales had higher incidence rates than white males.
• Of cancers linked to being overweight and obese, higher incidence rates were found among non-Hispanic blacks and non-Hispanic whites compared with other racial and ethnic groups.
• Cancers associated with overweight and obesity increased by 7 percent, not including colorectal cancer. During that same time there was a decrease of 13 percent in cancers not associated with overweight and obesity. There was also a 23 percent decrease in colorectal cancer, due in large part to screening.
• Cancers associated with overweight and obesity increased among 18 to 75 year-olds, not including colorectal cancer, (Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States, 2017)

Cancer and Obesity – What can you do?
Not all cases of the cancers mentioned above can be attributed to obesity or being overweight. However, excess body weight is a modifiable risk factor. What does that mean? It means that there are steps that a person can take to prevent obesity and decrease their risk of some types of cancer.

Stay Active: 150 minutes of moderate activity or 75 minutes of vigorous activity per week.

Eat a healthy diet: Fill your plate with fattier cuts of meats, healthy fats such as avocados and olive oil and non-starchy vegetables and fruit. Avoid processed foods.

Limit your alcohol intake: If you drink, limit yourself to one drink per day if you are a female and two a day if you are a male.

Get plenty of rest: being tired can lead to unhealthy choices and make you want to eat more. (How Does Obesity Cause Cancer, 2017)

There remain many unanswered questions about excess weight and cancer risk. Still, knowing the proven health benefits of losing weight, obese individuals are encouraged to get to and maintain a healthy weight. Working toward achieving a healthy weight will aid in reducing cancer risk while helping reduce other chronic illnesses.

INSPIRE Exercise Medicine
239.429.0800
www.Inspireem.com
3555 Kraft Road, Suite 130, Naples, FL 34105

References:
Cancers Associated with Overweight and Obesity Make up 40 Percent of Cancers Diagnosed in the United States. (2017, October 3). Retrieved from CDC Newsroom: https://www.cdc.gov/media/
releases/2017/p1003-vs-cancer-obesity.html
How Does Obesity Cause Cancer. (2017, June). Retrieved from The Univeristy of Texas MD Anderson Cancer Center:
https://www.mdanderson.org/publications/focused-on-health/
how-does-obesity-cause-cancer.h27Z1591413.html
Obesity and Cancer. (2022, April 5). Retrieved from National Cancer Institute: https://www.cancer.gov/about-cancer/causes-prevention/
risk/obesity/obesity-fact-sheet
Overweight/Obesity-Associated Cancers. (2021, November 30). Retrieved from Texas Health and Human Services:
https://www.dshs.texas.gov/tcr/data/obesity-associated-
cancers.aspx