Most of us know that obesity is linked to a wide range of health conditions, including Type 2 diabetes and heart disease. But the connection between obesity and cancer risk is perhaps less well known, even though science has now identified 11 types of cancer associated with obesity. Stomach cancer is the most recent addition to the list, added in 2016.
Here’s the current full list of cancers linked to obesity:
- Breast cancer (after menopause)
- Colon cancer
- Esophageal cancer
- Gallbladder cancer
- Kidney cancer
- Liver cancer
- Pancreatic cancer
- Prostate cancer
- Stomach cancer
- Thyroid cancer
- Uterine/endometrial cancer
How does obesity cause cancer?
“Excess fat is associated with chronic inflammation, which research has proven to be linked to cancer by promoting cell mutation and tumor growth,” says Thomas Froehlich, M.D., Medical Director of UT Southwestern’s Harold C. Simmons Comprehensive Cancer Center. The amount of fat we carry also influences our hormones, he adds, specifically our sex hormones and insulin levels, which researchers think have a major impact on cancer risk.
In men, for instance, obesity is related to lower testosterone levels, which may increase the risk for developing prostate cancer or lead to worse outcomes for those who already have the disease.
As for the opposite sex, studies have shown that obese women tend to have higher levels of estrogen than women of healthy weight, putting them at higher risk for breast cancer. Researchers think this hormone imbalance may contribute to cancer cell growth.
Regarding insulin, Dr. Froehlich notes that as abdominal fat increases, insulin production in the pancreas also increases. “Obese people often have elevated insulin levels, which can lead to insulin resistance, also known as hyperinsulinaemia,” he says. “Research has shown that hyperinsulinaemia increases the risk of certain cancers, including colon, endometrium, and kidney cancer.”
Reducing your risk
If obesity trends continue, there will be about a half-million additional cases of cancer in the U.S. by 2030, according to one study. National Cancer Institute data suggest that if every adult in the U.S. reduced his or her body mass index (BMI) by just 1 percent (about a 2.2 pound weight loss for the average adult) nearly 100,000 new cases could be avoided.
So how to reduce your cancer risk? “A study published in JAMA Oncology in May 2016 suggests that half of all cancer cases could be prevented if we incorporated just four lifestyle changes,” Dr. Froehlich reports:
- Drink alcohol in moderation or not at all. That means one drink per day for women and two for men – a drink is defined as 8 ounces of beer, 5 ounces of wine, or 1.5 ounces of spirits.
- Reduce your weight and bring your BMI to a level between 18.5 and 27.5.
- Exercise for at least 30 minutes a day, five days a week. Exercise may help decrease the risk for 13 types of cancer because of its impact on sex hormones, insulin, and inflammation within our bodies.
- Quit smoking, or don’t start if you’re a non-smoker.