Obesity has been linked with an increased risk of developing 10 different types of cancer. Many of these cancers are among the most deadly and common forms of cancer, including endometrial, colon, and breast cancer. Except for premenopausal breast cancer, obesity is a major risk factor for all other types of female hormone-related cancers. Increased body fat also increases the risk of stomach, oesophageal, pancreatic, and prostate cancer. The risk increases as the number of excess pounds and the waist circumference grow larger. The good news is that obesity can be prevented or effectively treated in most cases by eating better and moving more.
Obesity is a well-established risk factor for colorectal cancer (CRC). In fact, the link between obesity and CRC development is stronger than for any other type of cancer. Obesity increases the risk of developing CRC by about 40% in both men and women. This risk may be even higher for people with type 2 diabetes, who have about a 70% increased risk for CRC. The exact mechanism linking increased body fat with CRC development is not fully understood. It’s likely a combination of genetic and environmental factors associated with a high-calorie diet, such as increased insulin and insulin-like growth factor (IGF) levels, increased levels of free IGF-1 and insulin, and changes in the hormone IGF-1. These factors may increase the risk of CRC by interfering with DNA replication and repair or by interfering with the immune system.
Endometrial cancer is the most common type of cancer in women outside of the breast. While women with a body mass index (BMI) under 25 have about a 1 in 1,000 chance of developing endometrial cancer during their lifetime, those with a BMI over 35 have a 5 in 1,000 chance. While it’s not completely clear why obesity increases the risk of endometrial cancer, it’s believed that certain hormones (e.g., estrogens) are involved. Normally, these hormones help regulate the growth of the endometrial cells that line the uterus. But in obese women, these hormones may act in a different way, stimulating the growth of endometrial cells that are too numerous and too thick, which can lead to cancer.
Obesity is the main modifiable risk factor for pancreatic cancer, increasing the risk by about 70%. The risk for pancreatic cancer is also higher in people with type 2 diabetes, a condition that usually occurs in people with high blood sugar levels. There are several explanations for the link between obesity and pancreatic cancer, including insulin resistance and chronic low-level inflammation, which may affect the functioning of the immune system.
Prostate cancer is the second most common cause of cancer death in men after lung cancer. Although obesity is a known risk factor for prostate cancer, the association is not as strong as the link between obesity and pancreatic cancer. Yet, even with a weaker association, obesity still accounts for roughly one out of every seven prostate cancer cases. The exact reason why obesity increases the risk of prostate cancer is not fully understood. One theory suggests that fat cells may secrete certain compounds that promote the growth of prostate cancer cells. Alternatively, it’s possible that higher levels of insulin in obese people promote the growth of prostate cancer cells by activating certain enzymes that activate androgen receptors in the prostate.
There is a link between obesity and the risk of developing squamous cell carcinoma, the second most common type of skin cancer, after basal cell carcinoma. The exact mechanism linking obesity with squamous cell carcinoma is not clear. But it’s likely that the same mechanisms that increase the risk of other cancers, such as insulin resistance, might also increase the risk of skin cancer.
As many as 10% of breast cancers are thought to be caused by obesity. The risk of developing breast cancer is higher in premenopausal women, who have a stronger link between obesity and breast cancer than postmenopausal women do. By definition, obesity is a diagnosis based on BMI. But researchers are also starting to look at the number of fat cells a person has as a way to better understand and clarify the link between obesity and breast cancer.
Stomach cancer, also known as gastric cancer, is the fourth leading cause of cancer deaths worldwide, especially in East Asian countries. Obesity has been shown to increase the risk of developing stomach cancer by about two to four times among people of East Asian descent. The exact mechanism linking obesity and stomach cancer is not clear. But it’s likely that the same mechanisms that are involved in other cancers, such as insulin resistance, might also play a role in the development of stomach cancer.
Oesophageal cancer is the eighth most common type of cancer worldwide. It’s the third most common cause of death from cancer in Asia. The link between obesity and oesophageal cancer might be similar to the link between obesity and stomach cancer. Obesity has also been shown to increase the risk of developing Barrett’s esophagus, a pre-cancerous condition in the esophagus. Yet, the exact mechanism linking obesity with oesophageal cancer is not clear.
Obesity has been linked with an increased risk of developing 10 different types of cancer. The risk increases as the number of excess pounds and the waist circumference grow larger. The good news is that obesity can be prevented or effectively treated in most cases by eating better and moving more.