What you may have heard
Obesity has been linked to various types of cancers.
What science tells us
Obesity or high body mass index (BMI) is a condition in which a person has an unhealthy amount and/or distribution of body fat. To measure obesity, researchers often use the BMI scale, which is determined by dividing a person’s weight (in kilograms) by their height (in meters) squared. BMI provides a more accurate measure of obesity than weight alone, though it has its limitations. Nearly 70% of U.S. adults have a BMI of 25.0 or higher, which is characterized as overweight (25.0-29.9) or obese (30.0 and above) (NCI). However, there are many metrics of obesity, and each of these may be associated with different cancer risks.
There is consistent evidence that higher body fat is linked to a number of cancers. People with obesity have chronic inflammation, which, over time, can cause DNA damage that leads to cancer. These people are also more likely to have conditions or disorders that are linked to or cause chronic inflammation: for example, Barrett’s esophagus, gallstones, ulcerative colitis, and hepatitis(NCI). Cancers linked to obesity include:
- Endometrial: Obese and overweight women are 2-4 times as likely as women with a healthy BMI to develop endometrial cancer (cancer of the lining of the uterus). Risk of endometrial cancer increases with increasing weight gain in adulthood(NCI).
- Esophageal: People who are overweight or obese are 2 times as likely as those with a healthy BMI to develop esophageal adenocarcinoma (NCI).
- Gastric cardia: People who are obese are nearly twice as likely as those of healthy weight to develop cancer in the upper part of the stomach, closest to the esophagus (NCI).
- Liver: People who are overweight or obese are up to twice as likely as those of healthy weight to develop liver cancer; this association is stronger in men (NCI).
- Kidney: People who are overweight or obese are up to twice as likely as those of healthy weight to develop renal cell cancer, the most common form of kidney cancer (NCI).
- Multiple myeloma: Multiple myeloma is a cancer that forms in a specific type of white blood cell (plasma cell) and accumulates in the bone marrow. Compared to healthy-weight individuals, overweight and obese individuals have a 10-20% increase in risk of developing multiple myeloma (NCI).
- Meningioma: A meningioma is a slow-growing tumor that develops in the membranes surrounding the brain and spinal cord. The risk of meningioma is increased by 50% in those who are obese and 20% in those who are overweight.
- Pancreatic: People who are overweight or obese are about 1.5 times as likely to develop pancreatic cancer (NCI).
- Colorectal: People who are obese are 30% more likely to develop colorectal cancer than healthy-weight individuals (NCI).
- Gallbladder: People who are obese have a 60% increase in risk of gallbladder cancer (NCI).
- Breast: Women in menopause who are obese have a 20-40% increase in risk of developing breast cancer (NCI).
- Ovarian: Higher BMI is associated with a 10% increase in risk of ovarian cancer among women who have never used menopausal hormone therapy (NCI).
- Thyroid: Higher BMI is associated with a 10% increase in risk of thyroid cancer among women who have never used menopausal hormone therapy (NCI).
In people who are diagnosed with breast, prostate, or colorectal cancer, research shows that obesity may worsen aspects of cancer survivorship (example: quality of life, cancer recurrence, cancer progression, and survival).
Laboratory Evidence/Supporting Evidence
The laboratory and animal study evidence generally supports the epidemiological evidence that obesity is associated with risk of a variety of cancers.
IARC Carcinogen Classification: Not classified
How to reduce your risk
Epidemiological studies provide consistent evidence that people who have a healthy BMI have lower risk of colon, kidney, breast, endometrial, and ovarian cancers (NCI). Studies have shown that people who lose weight have decreased risk of breast, endometrial, colon, and prostate cancers. People with obesity who have bariatric surgery appear to have lower risks of obesity-related cancers than those who do not have bariatric surgeries.
The steps to prevent unhealthy weight gain are the same as the steps to lose weight: exercising regularly, maintaining a healthy diet, and monitoring your weight. To prevent weight gain, 150-300 minutes of moderate-intensity activity per week is recommended (Mayo Clinic). A healthy diet includes low-calorie and nutrient-dense foods (such as fruits, vegetables, and whole grains), avoids saturated fat, and limits sweets, alcohol, and processed foods. Identifying situations that trigger overeating and monitoring these situations can also prevent weight gain. Finally, consistency in diet and exercise, and monitoring your weight regularly can help keep off excess pounds.
Obesity increases risk of endometrial, esophageal, gastric cardia, liver, kidney, multiple myeloma, meningioma, pancreatic, colorectal, gallbladder, breast, ovarian, and thyroid cancers. The steps to prevent unhealthy weight gain are the same as the steps to lose weight: Exercise regularly, maintain a healthy diet, and monitor your weight.
Learn More From These Trusted Sources
National Cancer Institute (NCI): Obesity and cancer
MD Anderson: Obesity and cancer
CDC: Obesity and cancer
Mayo Clinic: Obesity
Published: June 24, 2021
Verified/Updated: August 22, 2022