Maintaining a healthy weight benefits your health in more ways than one. Not only does it put less strain on your muscles and joints and benefit your heart health, but it also reduces your chances of developing obesity, which puts you at a higher risk for developing cancer.
Keep reading to learn more about the cancer risks associated with obesity, including which ones are most common, the effects of losing weight and which screenings you should prioritize to protect your well-being.
Does Obesity Increase Cancer Risk?
According to the U.S. Centers for Disease Control and Prevention (CDC), obesity is linked to a heightened risk for at least 13 types of cancer, including breast, colon, liver and pancreas cancers. While researchers still don't know the exact connections between obesity and cancer, they believe that inflammation, cell growth and hormone changes caused by excess body weight play an important role.
The good news is that obesity is treatable, and the earlier you start losing weight, the better it is for cancer prevention. Knowing the potential link between obesity and cancer risk is why our doctors use this knowledge and take it seriously when it comes to cancer prevention.
Our clinicians also understand that there's a lot more to a person's health than whether they're at a healthy weight or working toward one. For this reason, we focus on your overall metabolic health, including your blood pressure, cholesterol levels, blood sugar (glucose) levels and waist circumference and not just the reading on the scale when personalizing your cancer prevention strategy.
Understanding Obesity
In clinical terms, obesity is a chronic health condition characterized by excessive body fat. Over the last few years, obesity has become a health crisis. According to the World Health Organization (WHO), in 2022, 1 in every 8 people in the world was living with obesity.
People often wonder what the difference is between being overweight and being obese. While both of these conditions are caused by carrying excess body fat, they are generally defined by a person's body mass index, or BMI:
- Overweight: a BMI of 25 to 29.9
- Obese: a BMI of 30 or higher
Another measurement doctors can use to assess a person's risk of obesity is waist circumference. This measures a person's abdominal fat — medically known as visceral fat — that accumulates around the midsection. In general, a waist circumference of about 32+ inches for women or 37+ inches for men is considered to be an elevated obesity risk. A waist circumference of 35+ inches for women or 40+ inches for men is considered high risk for obesity.
While excessive weight is the underlying factor for obesity, other key factors can increase a person's risk for obesity, such as:
- Eating an unhealthy diet of ultra-processed foods
- Genetics
- Hormonal imbalances
- Living a sedentary lifestyle and not exercising regularly
- Medications like antidepressants and steroids
- Metabolic disorders
- Sleeping issues
- Smoking
- Socioeconomic factors
Additionally, there are several health conditions and chronic diseases that can heighten a person's chance of developing obesity, including:
- Arthritis
- Congestive heart failure
- Cushing syndrome
- Depression
- Hashimoto's disease (hypothyroidism)
- Insomnia
- Menopause
- Metabolic syndrome
- Polyendocrine metabolic ovarian syndrome (PMOS)
- Prader-Willi syndrome
- Type 2 diabetes
It’s best to talk with your doctor about your family medical history to determine your chances of developing various conditions, which could increase your risk of obesity.
How Obesity Can Increase Cancer Risk
When talking about whether or not obesity causes cancer, it’s important to understand what effects obesity has on the body that might increase a person’s risk of developing cancer.
While there is still much to learn, past cancer research has identified a few specific effects that may play a role in cancer development.
Chronic Inflammation and Cell Signaling
One of the most well-known obesity factors that may drive the development of cancer is chronic inflammation. Scientists estimate that as much as 25% of all cancer cases globally are highly influenced or caused by chronic inflammation.
Inflammation is a normal sign that the body's immune system is fighting bacteria or a virus. However, once the body heals, the inflammation goes away.
With chronic inflammation, the immune system remains "on," even in the absence of sickness or injury. Over time, this constant state of inflammation can damage healthy tissues and organs, and can even lead to mutations in cells, which can be a driving force — called cell signaling — behind the creation of cancer tumors.
Insulin Resistance, Higher Insulin Levels and IGF Pathways
Mainly after eating carbs, the pancreas creates and releases insulin, which helps keep the body's blood sugar levels under control.
Conversely, obesity causes insulin resistance, in which the body's cells can't absorb blood sugar as they normally would, leading the pancreas to produce too much insulin.
These high insulin levels, known as hyperinsulinemia, can also increase the pathway for insulin-like growth factor-1 (IGF-1). IGF-1 is known to promote the growth of cancer cells, increasing the risk of certain cancers.
Hormone Changes (Especially Estrogen)
Hormones play an extremely important role in maintaining your body's health. They help manage stress, regulate your reproductive system, keep your metabolism humming along and regulate certain body functions.
Obesity can disrupt the endocrine system, affecting the normal release of hormones. This can cause elevated levels of insulin and the hunger hormone leptin, as well as imbalances in the sex hormones estrogen in women and both testosterone and estrogen in men.
The higher levels of estrogen created by obesity can increase a woman's risk for certain cancers, including breast, endometrial and ovarian cancers.
Immune Function and Surveillance
Chronic inflammation can harm the immune system, making it less effective at fighting diseases and infections. Having an impaired immune system also means that its job of keeping an eye out for cancerous cells — or surveillance — is weakened. This can make it much easier for cancer tumors to grow.
Additionally, previous research shows that people who are obese are generally less responsive to the benefits of vaccines due to their weakened immune system. This means that receiving vaccines for cancers, such as the HPV vaccine, may not offer as much protection in people who are obese.
Fatty Liver and Metabolic Changes
When you're obese, you carry more body fat — medically known as adipose tissue — in your body. Normally, adipose tissue releases free fatty acids (FFAs), which travel through the bloodstream to deliver energy to different parts of the body.
Having too much adipose tissue can lead to excessive FFA release, which, in turn, can overwhelm and harm the liver. This can potentially lead to diseases like metabolic syndrome and nonalcoholic fatty liver disease (NAFLD), also sometimes called metabolic dysfunction-associated steatotic liver disease (MASLD).
What does this have to do with obesity and cancer risk? Fatty liver disease is a known risk factor for not only liver disease, but also kidney, colorectal, bladder and breast cancers.
The Gut Microbiome and Digestive Health
Over the last few years, medical professionals have gained a greater understanding of the gut microbiome and its important role in our overall health, including cancer prevention.
Obesity can alter the diversity of bacteria and other microorganisms in the microbiome, leading to chronic inflammation and metabolic issues that can harm the liver and pancreas.
Gut microbiome imbalance, known as dysbiosis, has been linked to an increased risk for several types of cancer, including colorectal, gastric, liver, pancreas, gallbladder and breast cancers.
Which Cancers Are Most Associated With Obesity?
When thinking more about the question, does obesity cause cancer, let’s talk more about the different types of cancers that are frequently associated with obesity.
Hormone-Related Cancers
By unbalancing the body's hormones and causing chronic inflammation, obesity can heighten a person's risk for several types of cancer, including:
- Breast cancer (postmenopausal)
- Endometrial cancer
- Gallbladder cancer
- Kidney cancer
- Liver cancer
- Ovarian cancer
- Pancreatic cancer
- Thyroid cancer
Digestive System Cancers
The gut microbiome alterations caused by carrying excess weight can increase a person's risk for cancers such as:
- Colorectal cancer
- Esophageal cancer
- Gallbladder cancer
- Liver cancer
- Pancreatic cancer
- Stomach cancer
Metabolic-Organ Cancers
The negative impact that obesity has on the body's hormones, insulin levels, immune system, inflammation levels, liver health and gut microbiome has the potential to cause an increased risk for these cancer types:
- Adenocarcinoma (cancer in the glandular cells)
- Breast cancer
- Colorectal cancer
- Endometrial/uterine cancer
- Esophageal cancer
- Gallbladder cancer
- Kidney cancer
- Liver cancer
- Meningioma (type of brain cancer)
- Multiple myeloma (cancer in the blood plasma cells)
- Ovarian cancer
- Pancreatic cancer
- Stomach cancer
- Thyroid cancer
Now that we have a better understanding of how obesity affects the body, let’s look at how it can affect cancer treatment.
The Impact of Obesity on Cancer Treatment
While there are links between obesity and many causes of cancer, carrying excess weight and fat cells can also negatively impact cancer treatment.
If you're receiving cancer treatment, obesity can impact the effectiveness of:
- Chemotherapy: Excess adipose tissue can reduce chemotherapy's effectiveness.
- Hormone therapy: Obesity can lessen the effectiveness of hormone therapy for certain hormone-driven cancers, such as breast and prostate cancers.
- Radiation therapy: Excess body fat and tissue can make it difficult for a radiation oncologist to target your tumor.
- Surgery: Obesity can increase your risk for surgical complications, such as infections and excessive blood loss.
The good news is that losing weight can potentially lower that risk.
Does Losing Weight Reduce Cancer Risk?
While there is a clear link between obesity and cancer risk, past studies show that losing 5% to 10% of your body weight may help prevent cancer because of the health benefits you gain when you reach a healthy weight, such as:
- Better control or remission of Type 2 diabetes
- Decreased hormones, such as estrogen and insulin
- Improved cholesterol levels
- Improved insulin sensitivity
- Increased energy, allowing you to be more active
- Lessened risk for heart diseases such as coronary artery disease, heart attack and stroke
- Lower blood pressure
- Potential reversal of liver scarring (fibrosis) in people with metabolic dysfunction-associated steatotic liver disease (MASLD)
- Reduced chronic inflammation
- Remedied sleeping issues, such as sleep apnea
- Resolved mood disorders, such as depression and anxiety
Today, there are several healthcare options that can help people lose weight, including:
- Following a scheduled meal time plan, such as intermittent fasting
- Making healthy lifestyle changes through diet and physical activity
- Medical procedures like bariatric surgery
- Nutrition counseling through a nutritionist or physician
- Structured meal replacement program
- Taking medications, such as a GLP-1
And it’s important to note that cancer prevention is not just about losing weight. Many other factors can increase your cancer risk, regardless of whether you’re at a healthy weight or not, such as:
- Age, especially after the age of 50
- Certain infections, like the human papillomavirus (HPV), hepatitis B, Epstein-Barr virus and human immunodeficiency virus (HIV)
- Eating a diet high in ultra-processed foods, sugary drinks and red or processed meats
- Environmental exposure to carcinogens and chemicals in the air or at work
- Family history or inherited gene mutations can potentially heighten risks for certain cancers, such as the risk of breast cancer
- Living a sedentary lifestyle without any regular exercise
- Moderate (one to two drinks a day) or heavy (three or more drinks a day) alcohol use
- Tobacco use, including smoking, chewing tobacco, vaping and exposure to secondhand smoke
- UV radiation exposure, such as from a tanning bed or being out in the sun without sunscreen or protective clothing
Now that you have a better understanding of how or if obesity causes cancer, it’s important to remember that cancer can occur regardless of your weight.
Screening and Early Detection: What to Prioritize
Regular cancer screenings are a vital part of your preventive health plan. Cancer screenings that everyone should have, regardless of weight, include:
- Breast cancer: Women should begin having annual mammograms by age 45.
- Cervical cancer: Women ages 25 and older should be screened via an HPV test every three to five years, performed during a routine Pap smear.
- Colorectal cancer: For most people, starting at age 45, screening with stool-based samples every one to three years or with colonoscopies every 10 years is recommended.
- Liver cancer: Abdominal ultrasounds performed every six months are used to help screen for liver cancer in adults with cirrhosis, hepatitis B or obesity.
- Lung cancer: Whether you smoke or have quit within the last 15 years, an annual CT scan is recommended for adults ages 50 to 80.
- Prostate cancer: Men should be screened starting at age 45 for those with a family history, or by age 50 for those at average risk of prostate cancer.
- Skin cancer: Adults can start to have annual skin cancer checks by a dermatologist as early as their 20s, especially if they are considered high risk. Annual screenings are highly recommended after age 35.
If you’re unsure where to start, you can feel confident that our compassionate providers are here to guide you and answer any questions you have as you journey toward wholeness.
Preventive Healthcare for a Life of Wellness
There’s no denying that the added stress and complications obesity places on the body can increase your risk of developing cancer. But help is available, and we’re ready to guide you on your journey to losing weight and keeping it off. If you're ready to be the healthiest you can be, our doctors at our weight loss and bariatric surgery centers are here to help. Our knowledgeable medical team will assess your current health and walk you through your options.
To learn more about obesity and cancer risk, and to schedule your regular cancer screenings, make an appointment today with your AdventHealth primary care physician.
