Béo phì và nguy cơ ung thư: Những bằng chứng mới nhất cho thấy điều gì?

Obesity is now recognized as one of the leading preventable risk factors for cancer, contributing to the development of at least 13 cancer types. As obesity rates continue to rise worldwide, researchers are uncovering new ways excess body fat may influence cancer development.  Several factors can influence the risk, including the cancer type, sex, and fat distribution. 

In this article, we will discuss the potential mechanisms by which excess body weight may make you more likely to get cancer. We will also answer the most frequently asked questions. 

Obesity and Cancer Risk: Quick Facts

• Being overweight or obese is associated with a higher risk of 13 cancer types. These 13 cancers account for about 40% of all cancers diagnosed annually in the United States. 
• Researchers predict that obesity may soon surpass smoking as the top cause of cancer in the US [1].
• Excess body weight may drive cancer risk by increasing long-term inflammation and disrupting hormonal balance in the body. 
• Sustained weight loss may help lower cancer risk. 

What Is Obesity?

Being overweight or obese means your body weight is higher than what is considered normal for your height. In the U.S., a screening tool called the Body Mass Index (BMI) is used to determine whether a person is overweight or obese. 

An adult with a BMI between 25 and 29.9 is considered overweight. Likewise, obesity for an adult is when their BMI is 30 or higher. 

According to the Centers for Disease Control and Prevention (CDC), over 2 in 5 US adults are obese [2].

Being overweight or obese may increase your risk of getting many diseases, including [3]:

• Bệnh tiểu đường
• Huyết áp cao
• Diseases of the heart and blood vessels
• Đột quỵ

Although BMI is widely used for screening, it does not directly measure body fat and may not accurately reflect health risk in every individual. 

What Are the Cancer Types Associated With Obesity?

Of more than 100 types of cancer, the following have direct links to overweight or obesity [2]:

1. Adenocarcinoma of the esophagus (cancer that starts in certain regions of the food pipe)
2. Breast (in women who no longer have monthly periods; postmenopausal)
3. Colon and rectum
4. Uterus
5. Gallbladder
6. Upper stomach
7. Kidneys
8. Liver
9. Ovaries
10. Pancreas
11. Tuyến giáp
12. Meningioma (cancer that starts in the protective covering of the brain and spinal cord)
13. Bệnh đa u tủy (cancer that forms in a certain type of white blood cell)

This is an active area of research, and scientists are investigating if obesity could drive the risk of other cancers. For example, a 2023 study involving over 2 million people and a 9-year follow-up found a link between 18 cancers and being obese/overweight [4].

Although obesity increases the risk of several cancers, it does not mean a person will develop cancer. Factors such as age, genetics, smoking status, alcohol use, physical activity, and environmental exposures also influence cancer risk. 

Obesity and Cancer Risk: What Are the Potential Mechanisms?

Researchers have suggested several mechanisms through which obesity may drive cancer risk.

Chronic Inflammation

Overweight or obese people often have chronic low-grade inflammation. While inflammation is protective, when it lingers for a longer period, it can create a “host environment” where cancer cells can grow and multiply. 

High Estrogen Levels

High estrogen levels due to excess production by fat cells may increase the risk of breast, endometrial, and ovarian cancer. 

High Levels of Insulin and Other Factors

Overweight or obese people usually have high levels of insulin and insulin-like growth factor-1 (IGF-1). Some cancer cells may use these growth factors to divide without limit. Elevated levels of insulin and IGF-1 may increase the risk of thyroid, breast, colon and rectum, prostate, ovarian, and endometrial cancers. 

Disruption of Hormones That Regulate Cell Growth

Many hormones regulate cell growth in human beings, including adipokines produced by fat tissue. Adipokines can stimulate or arrest cell growth, depending on the specific type. 

Obesity can disrupt the balance between these hormones, potentially increasing cancer risk. For example, levels of adiponectin (an adipokine that may limit cell growth) are low in people with obesity. 

Immune Suppression

Animal studies show that obesity can make T cells less powerful in their fight against cancer. For example, in a mouse study, researchers found that T cells in obese mice had problems entering the tumor. Even though some managed to get inside the tumor, they were unable to function [5].

Obesity and Cancer Risk: How Fat Distribution Might Affect the Risk

In some obesity-related cancers, the location of fat might be just as crucial as how much there is in the body. 

For example, in a 2025 study, researchers investigated the link between 12 obesity-related cancers and fat distribution in five different parts of the body:

1. Abdominal fat
2. Visceral fat (surrounding the organs inside the abdomen)
3. Fat on the buttocks and thighs
4. Liver fat 
5. Pancreas fat

They found the following [6]:

• Abdominal fat was linked to increased risk of endometrial cancer, liver cancer, and esophageal adenocarcinoma. 
• Fat on the buttocks and thighs was linked to a lower risk of breast cancer and a type of brain cancer (meningioma). 
• Higher visceral fat and liver fat increased the risk of liver cancer. 

Obesity and Cancer Risk: Does Gender Make a Difference?

Among obesity-associated cancers that occur in both men and women, cancer of the food pipe (esophageal adenocarcinoma) is nine times more likely to occur in men than in women in the U.S. [7].

Postmenopausal breast cancer is the most frequent obesity-related cancer among U.S. women. In U.S. men, the most frequent obesity-related cancer is colorectal cancer. 

Obesity and Cancer Risk: Frequently Asked Questions

Can losing excess weight reduce cancer risk?

Studies suggest that sustained weight loss, particularly losses of around 10% of body weight or more, may provide meaningful reductions in cancer-related risk factors [8].

What is 90% of cancer caused by?

Many cancers are influenced by environmental and lifestyle factors such as tobacco use, obesity, diet, alcohol consumption, infections, and UV exposure. Estimates vary, but researchers generally agree that a large proportion of cancers (up to 90%) may be preventable through risk-factor modification. [9].

Does obesity affect cancer survival?

Obesity appears to have a dual role in cancer survival. It is a risk factor for overall cancer-related deaths. However, some studies have observed better outcomes among patients with certain cancers who have obesity, a phenomenon known as the “obesity paradox.” Researchers continue to debate whether this reflects a true biological effect or limitations in how body composition is measured [10].

Can childhood obesity affect cancer risk in adulthood?

While the underlying mechanisms are poorly understood, childhood and adolescent obesity is strongly associated with blood cancer, breast cancer, and colorectal cancer [11].

Phần kết luận

Obesity is a complex condition that affects far more than body weight alone. Growing evidence suggests that excess body fat can influence cancer risk through chronic inflammation, hormonal changes, immune dysfunction, and metabolic disturbances. While obesity does not guarantee that a person will develop cancer, maintaining a healthy weight through diet, physical activity, and other lifestyle measures may help reduce risk. As researchers continue to uncover the links between obesity and cancer, preventing and treating obesity remains an important strategy for improving long-term health.