The COVID-19 pandemic has made significant changes in our lives. Countries and individuals took many steps to limit the infection rate. Surprisingly, no one ever thought about another ongoing pandemic: obesity! According to the CDC, 42.4% of adults in the USA are obese (1). A side-effect of obesity that is not discussed is cancer. Studies found that obesity and cancer are positively correlated, with 28,000 new cancer cases in men and 72,000 in women caused by obesity (in 2012) (2).
Is Body mass index (BMI) a reliable measure of obesity and cancer risk?
Before diving into the details, let’s understand what obesity is.
Obesity is defined as excessive fat accumulation with a BMI over 25 being overweight and over 30 is obese. BMI is calculated by dividing your weight in kg by your height in meters squared (weight / height2
Here are the different weight categories based on BMI for 20-years-old adults or older.
| BMI in kg/m2 | Weight Category |
| <18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25 – 29.9 | Overweight |
| >30 | Obese |
It is an accurate way to measure your body fat. Still, it has nothing to do with the relation between obesity and cancer.
What are the 6 types of cancers associated with obesity?
Unfortunately, the list is much longer than 6 types! Up to 13 types of cancer are related to obesity, highlighting the strong correlation between obesity and cancer. We will analyze only the most common ones.
Obesity and cancer of the endometrium
Endometrial cancer is a type of uterus cancer that originates from the inner lining of the uterus. Studies found that 57% of endometrial cancer cases in the USA are attributable to obesity and overweight (3).
Obesity and cancer of the esophagus
The esophagus is the tube that connects your mouth to the stomach. Similar to endometrial cancer, individuals in the highest quartile for body mass index (BMI) have a 7-fold increased risk for esophageal cancer (4).
Obesity and liver cancer
Believe it or not, being obese is associated with an 87% rise in liver cancer risk! Also, for every 5 kg/m2 rise in BMI, there is a 25 and 38 percent increase in liver cancer risk from women and men, respectively (5).
Obesity and pancreatic cancer
According to a study that analyzed 14 different studies, obesity and cancer were highly correlated when it comes to the pancreas. It was found that obese people are 1.5 times more likely to develop pancreatic cancer than normal-weight people (6).
Other types of cancers associated with obesity include (7):
- Breast cancer
- Ovarian cancer
- Thyroid cancer
- Gallbladder cancer
- Colorectal cancer
- Pancreatic cancer
- Meningioma (a type of brain cancer)
- Multiple myeloma ( a type of blood cancer)
- Kidney cancer
- Stomach cancer
Which cancer is most associated with obesity?
According to the CDC, colon cancer is the most common obesity-related tumor among males. In contrast, breast cancer is the most common obesity-related tumor among post-menopause females (8). Again, this highlights the apparent correlation between obesity and cancer.
Does losing weight reduce cancer risk?
Yes!
The good news is that you can lower your risk of developing obesity-related cancer by weight loss.
Studies reported that breast cancer risk was lowered by 50% in women who intentionally underwent weight loss higher than 10 kg (9). Similarly, obese patients who underwent bariatric surgery and achieved an average of 20 kg weight reduction had a significant decrease in cancer incidence (10).
Take-home point
The prevalence of obesity and its complication is alarming. In addition to increased risk of hypertension, heart disease, and diabetes, obesity increases the risk of many cancers, including breast, colon, esophageal, and endometrial cancer. This can be prevented by proper dieting and weight loss.
References
- https://www.cdc.gov/obesity/data/adult.html#:~:text=The%20US%20obesity%20prevalence%20was,from%204.7%25%20to%209.2%25.
- https://pubmed.ncbi.nlm.nih.gov/25467404/
- https://pubmed.ncbi.nlm.nih.gov/27903150/
- https://pubmed.ncbi.nlm.nih.gov/22898040/
- https://cancerres.aacrjournals.org/content/76/20/6076
- https://pubmed.ncbi.nlm.nih.gov/21105029/
- https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet#r17
- https://www.cdc.gov/cancer/obesity/index.htm
- https://pubmed.ncbi.nlm.nih.gov/7612801/
- https://pubmed.ncbi.nlm.nih.gov/19556163/