How much does obesity increase my cancer risk?

Mar 6, 2026

Today, more than four in 10 U.S. adults live with obesity, and globally, the prevalence has nearly tripled over the past several decades. These trends matter for our health—not only because of their links to heart disease and diabetes, but also because obesity is associated with increased cancer risk.

But maintaining a healthy weight can be challenging. Weight and health are shaped by many factors beyond individual choice, including genetics, access to healthy foods, opportunities for physical activity, stress and the environments in which we live and work.

The good news? Even with some of these hurdles, there may be changes you can make toward a healthier lifestyle. Knowing how obesity and cancer are linked can you take meaningful steps to lower your cancer risk and support your long-term health.

What is obesity?

Obesity is most often defined using body mass index (BMI), a screening tool that compares weight to height.

Overweight: BMI of 25.0–29.9
Obesity: BMI of 30.0 or higher

While BMI is useful for understanding population trends, it does not tell the whole story. It is possible to have a high BMI with low body weight, which would keep you at average risk of cancer. You can also have a low BMI, but have other factors—such as waist circumference and fat distribution—impacting your risk (specifically, excess fat around the abdomen is linked to higher cancer risk). Your health care provider can help you understand these measurements and assess your risk.

How can obesity increase my risk of cancer?

Your body can be impacted by obesity in different ways, some of which can increase the risk of cancer:

Inflammation

Having excess body fat promotes chronic, low-level inflammation. This ongoing inflammation can damage cells and DNA, creating conditions that allow cancer to develop and grow.

Hormonal changes

Obesity can also impact your hormones. Fat tissue produces hormones, including estrogen, and higher estrogen levels are linked to an increased risk of postmenopausal breast cancer and endometrial cancer. Obesity is also associated with higher levels of insulin—which is linked to diabetes—that can allow for abnormal cell growth.

Metabolic dysfunction

Obesity often leads to insulin resistance and altered metabolism, or changes to the body that can disrupt normal cellular processes and create abnormal growth. This can lead to the creation of cancer cells.

Effects on the immune system

If you’re immunocompromised, this can allow for abnormal cell growth. Obesity can impair the immune system’s ability to detect and eliminate abnormal cells, reducing one of the body’s natural defenses against cancer.

Having obesity results in a higher risk of cancer compared to being overweight; however, any excess weight can increase your risk of cancer.

What types of cancer are linked to obesity?

Research shows strong and consistent links between obesity and at least 13 types of cancer.

Cancers with the strongest evidence include:

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Endometrial cancer
Postmenopausal breast cancer

Other cancers associated with obesity include:

Esophageal adenocarcinoma
Gallbladder cancer
Gastric cancer
Kidney cancer
Liver cancer
Multiple Myeloma
Ovarian cancer
Pancreatic cancer
Thyroid cancer
Uterine cancer

Together, these cancers represent a significant portion of cancer diagnoses each year.

What makes obesity a modifiable cancer risk factor?

It is important to be clear: Although obesity can increase your cancer risk, it does not mean cancer is inevitable. Many people living with obesity will never develop cancer, and many people diagnosed with cancer do not have obesity.

What makes this issue especially important is that obesity is modifiable—it is often something you can change. Lifestyle changes can reduce risk and improve health outcomes.

Reducing cancer risk starts with making it easier for people to maintain a healthy weight throughout their lives. Along with getting routine cancer screenings and avoiding tobacco, being physically active and eating a healthy diet are key behaviors for losing weight. These activities also have a positive impact on your cancer risk separate from weight loss.

Physical activity is known to reduce inflammation, improve insulin sensitivity and support immune function. Similarly, eating a healthy diet with lots of fruits, vegetables, whole grains and lean proteins, and limiting ultra-processed foods, can improve your metabolic health and lower your cancer risk.

Prioritizing your health can feel overwhelming, but small steps add up. Talking to your health care provider is a powerful first step. Not sure where to start? Use this tool to find a doctor and schedule an appointment with a provider today.