Obesity has emerged as a global health concern since it directly leads to multiple metabolic and health conditions including diabetes and cardiovascular diseases. While it has been associated with metabolic disorders and cardiovascular diseases, excess weight can also be a significant risk factor for different types of cancer. “Obesity is one of the major preventable causes of cancer”, says Dr G Krishna Reddy, medical oncologist, Manipal Hospitals, Vijayawada, Andhra Pradesh. He adds that there is sufficient evidence to suggest that obesity, including excess belly fat, is associated with a heightened risk of developing at least 10 different types of cancer.
Dr Nishith Modi, surgical oncologist, HCG Cancer Centre, Vadodara, explains that excess body weight can lead to chronic inflammation, insulin resistance and hormonal imbalances, which can promote the development of cancer cells in the body.
Dr Mehr Prasad, endocrinologist, Fortis Hospital, Chennai, explains that in a person with obesity, the adipose tissue or the excess fat tissue is a major endocrine organ. So, whatever fat is stored in the body is like a big bag of hormone-producing organs. They produce a lot of hormones, cytokines (small proteins) and inflammatory agents, which increase the risk of cancers.
Kinds of cancer that obesity can cause
1. Adenocarcinoma of the esophagus (esophageal cancer)
Dr Reddy explains that obesity, especially abdominal obesity, increases gastroesophageal reflux. Dr Modi explains that this chronic reflux can lead to Barrett’s esophagus (a condition where the lining of the esophagus is damaged and turns red).
Because of the change in the esophageal lining and the inflammation of the esophagus, the chances of developing adenocarcinoma, a type of esophageal cancer, goes up.
2. Breast cancer
Postmenopausal women with obesity have a risk of developing breast cancer. Dr Prasad explains that for them, the adipose tissue produces excess estrogen, which can increase the risk of developing breast cancer. Obesity is associated with both a heightened risk of developing breast cancer and a worse prognosis after the onset of the disease.
3. Colorectal cancer
Excess body fat increases chronic inflammation and insulin resistance. Dr Prasad explains that the cytokines produced can more significantly cause colorectal cancer. He adds that because of the food choices people with obesity might sometimes make, there are a lot of changes in the gut microorganisms, which can lead to greater risks of colorectal cancer.
4. Gallbladder cancer
Dr Reddy explains that obesity augments the risk of gallstone formation, which is a risk factor for gallbladder cancer. Dr Modi adds that obesity also causes higher levels of certain hormones, chronic inflammation and metabolic abnormalities, all of which can contribute to developing gallbladder cancer.
5. Liver cancer (hepatocellular cancer)
Experts state that obesity can contribute to the development of non-alcoholic fatty liver disease (NAFLD). Dr Modi explains that NAFLD can progress to liver inflammation and eventually lead to cancer. “NAFLD causes hepatitis, which leads to cirrhosis and hepatocellular carcinoma”, says Dr Reddy. He adds that the prevalence of NAFLD is 30 per cent in the general population, but 90 per cent in morbidly obese adults.
Apart from this, obesity is associated with other factors that can increase the risk of liver cancer. “Obesity causes insulin resistance, elevated levels of certain hormones and chronic inflammation, all of which can promote the growth of liver cancer cells”, says Dr Modi.
6. Ovarian cancer
Excess fatty tissue and hormonal changes in women with obesity increase their chances of developing ovarian cancer. Dr Prasad explains that the bag of hormone-producing organs (excess fat in the body) in these women heightens estrogen levels, too. This rise in estrogen levels and other hormones escalates the risk of ovarian cancer.
7. Pancreatic cancer
Obesity causes insulin resistance. “Insulin levels go up very significantly in a person with obesity, which can increase the risk of pancreatic cancer”, says Dr Prasad.
He explains that there is a rise in activity in the islet cells (pancreatic cell that produces hormones, including insulin) in a person with obesity. Moreover, insulin itself is a carcinogen that can increase the risk of cancer.
8. Thyroid cancer
Excess weight and hormonal imbalances can contribute to developing thyroid cancer. “Obesity is associated with higher estrogen levels, which can stimulate the growth of thyroid cells and increase the risk of thyroid cancer”, says Dr Modi.
Dr Reddy explains that dysregulation of the immune system in the adipose tissue of a person with obesity leads to chronic low-grade inflammation. These inflammatory cytokines play a role in thyroid cancer. Obesity promotes high concentrations of adipokines (protein secreted by adipose tissue), which could lead to the formation of cancer in the thyroid gland.
9. Meningioma (a type of brain cancer)
Experts state that the exact mechanisms connecting obesity and meningioma are not yet fully understood. However, Dr Modi says that it is believed that obesity causes meningioma through hormonal imbalances, chronic inflammation and the release of certain growth factors that can promote the growth of tumor cells in the meninges (the protective membranes around the brain).
Experts state that studies show that meningioma is also more common in women. “It might be related to endogenous hormonal factors since obesity is associated with higher levels of estrogen and other growth factors”, says Dr Reddy.
10. Prostate cancer
“Obesity is associated with aggressive and high-grade prostate cancer”, says Dr Reddy. Experts state that the association between obesity and prostate cancer is complex.
Dr Modi explains that obesity can contribute to decreased testosterone levels, which can promote the growth of prostate cancer cells. Dr Reddy explains that periprostatic white adipose tissue (an endocrine organ that stores lipids) expansion in people with obesity leads to the induced secretion of cytokines and adipokines from certain cells in the tumor stroma, which could lead to cancer aggressiveness and therapy resistance. “Obesity is associated with chronic inflammation and insulin resistance, which may also contribute to the development and progression of prostate cancer”, says Dr Modi.
Because of chronic inflammation, hormonal imbalances, insulin resistance and metabolic abnormalities, obesity can also cause cancer in the uterus, kidney and upper stomach, as well as multiple myeloma. Experts state that maintaining ideal body weight through a healthy lifestyle and regular screenings can reduce the risk of cancer significantly.
