Overweight, obesity, and cancer? What do these three have in common, and why is cancer in the mix? Most people know that being overweight and obese can lead to certain health problems, including diabetes, heart disease, and high blood pressure. But did you know that it's also linked to cancer?
The link between these three is not just an interesting fact: it's a matter of life and death. Being overweight or obese has been seen to increase the risk of developing at least 13 types of cancer (CDC). In fact, being overweight or obese is associated with at least 30% of all cancer deaths worldwide (WHO).
The link between overweight, obesity, and cancer has been well documented by researchers. One study found that people who are obese have a higher risk of developing cancer than those who are not overweight. In fact, excess weight is thought to account for about 20% of all cancers in the United States—that's more than smoking!
With this information in mind, it's important to understand how being overweight or obese can increase the risk of developing cancer. Here's what the experts say:
Overweight, Obesity, and Cancer
The fact that obesity is linked to cancer is not news. Obesity and cancer are two of the most common health concerns for both men and women globally, and according to the World Health Organization (WHO), both overweight and cancer are global epidemics.
The WHO defines overweight as a body mass index (BMI) of 25 or greater—and obesity as a BMI of 30 or greater, and cancer as a group of diseases that occurs when abnormal cells grow uncontrollably or spread to other parts of the body.
Worldwide, more than 1 billion people are obese; more than 2 billion are overweight (WHO), and 19.3 million new cancer cases are recorded yearly.
The relationship between obesity, cancer risk, and mortality is complex and not clear-cut. Some studies suggest that being overweight or obese may raise your chances of getting some cancers, while other studies show no link between being overweight or obese and getting cancer at all. The link between this trio isn't well understood yet by scientists; however, there are several theories about why this might be true. One theory suggests that fat cells produce hormones called adipokines (adipose tissue-derived proteins) which are released into the bloodstream when someone gains weight. These adipokines affect the body's immune system by stimulating inflammation which may lead to cancer development over time.
The International Agency for Research on Cancer (IARC) has classified obesity as a Group 1 carcinogen, meaning that it definitely causes cancer. The World Health Organization (WHO) classifies obesity as a risk factor for cancer. According to these reports, the link between obesity and cancer is well established—it's stronger than the relationship between smoking and lung cancer, for example. It's also stronger than the relationship between alcohol intake and breast cancer. Here's what the research says about the link between overweight, obesity, and cancer risk.
Another theory suggests that excess fat tissue releases growth factors that stimulate cell growth in other areas of the body causing them to divide more quickly than usual which can lead to abnormal cell growth (cancer).
In 2012, researchers from the American Cancer Society examined more than 1 million men and women in North America who had never smoked or used tobacco products. They found that as body mass index increased (BMI), so did their risk of developing cancers of the esophagus (the tube linking your throat to your stomach), kidney or renal pelvis, liver/gallbladder/bile ducts, pancreas (cells that produce digestive enzymes), colorectum (lower part of your large intestine), endometrium (lining of the uterus; womb) prostate gland (male reproductive system), post-menopausal breast tissue, etc.
What may surprise you is just how closely the two are entwined. The link between cancer and obesity is not new, but it's getting stronger. And it's not just about weight: It's also about risk factors like body mass index (BMI), physical activity level, diet, and other lifestyle factors that are strongly linked to both obesity and cancer risk.
The link between obesity and cancer is so strong that researchers have created a term to describe it: "obesity-associated cancer." And it's not just one or two types of cancer that are linked to obesity—there are at least 13 different types.
Obesity-Associated Cancer
As the name implies, these are different types of cancer linked or closely associated with obesity or overweight.
According to a study published by The Lancet in 2015, the number of cancers caused by excess weight has increased over the past decades. It's estimated that about 14% of all cancers worldwide are caused by excess body weight; this means that about 55% of cancers diagnosed in 2012 were due to excessive body fat. The link between obesity and cancer is well documented: many types of cancer are more common among obese people than non-obese people, and being overweight has been associated with an increased risk for many cancers.
The different types of cancer that have been linked to overweight and obesity include:
- Adenocarcinoma of the esophagus.
- Breast (in women who have gone through menopause).
- Colon and rectum (colorectal).
- Uterus.
- Gallbladder.
- Upper stomach.
- Kidneys.
- Liver.
- Ovaries.
- Pancreas.
- Thyroid.
- Meningioma (a type of brain cancer).
- Multiple myeloma.
The most common include colorectal, breast, kidney/renal cell, endometrial, pancreatic, and esophageal cancers, and those with the strongest links to obesity are: breast cancer, colorectal cancer, endometrial cancer, kidney cancer, liver cancer, pancreatic cancer, and esophageal adenocarcinoma (cancer of the esophagus), according to data from the National Cancer Institute (NCI).
Being overweight or obese may increase your risk of developing colorectal cancer by 25 percent; breast cancer by 20 percent; endometrial cancer by 50 percent; kidney cancers by 50 percent; liver cancer by 20 percent; pancreatic cancer by 30 percent; esophageal cancer by 60 percent; gallbladder cancers by 50 percent; prostate cancers by 20%; ovarian cancers.
In fact, there are many connections between these conditions—and understanding them could help doctors better identify high-risk patients who may benefit from early intervention before they develop a full-blown disease.
Lowering the Risk of Obesity-Associated Cancer
As with many other health problems linked to obesity, this is not to say that every obese person will develop cancer; it's just that they're more likely than someone who maintains a healthy weight to develop cancer or one of the other conditions mentioned above.
If you are overweight (a BMI between 25–29), then your risk of developing these conditions increases by 20%. If you are obese (a BMI above 30), then your risk increases by 50% compared with people who have a normal BMI between 18.5–25 kg/m2.
Many doctors believe that those who maintain a healthy weight throughout their lives will have less risk of developing a range of diseases and conditions, including certain types of cancer.
Maintaining a healthy weight throughout life is key to reducing your chances of developing certain types of cancer. Weight loss can help reduce your risk, which means that losing weight after you've reached middle age can help reduce your risk even more. For example, if you had high blood pressure or diabetes at age 40 and then lost 10 pounds (5 kilograms), it might drop your blood pressure and lower your chance of getting heart disease or stroke in the future. And if you lose weight as an adult, it could lower the chances of getting colorectal cancer by 12-24%.
It's not just about gaining back some pounds after they've been lost, either: keeping them off with regular exercise and healthy eating habits will keep those benefits going. The World Cancer Research Fund (WCRF) estimates that 1/3rd of cancers could be prevented by maintaining a healthy body weight throughout life; if we could all do so globally, 2 million deaths could be avoided each year as well!
But even if you weren’t always at a healthy weight, it’s never too late to make changes for your health. And for some people with elevated cancer risk due to family history or a genetic mutation like BRCA1/2, these changes can make an even bigger difference.
Think of your body as a house, it needs the right kind of fuel to run properly and efficiently. Think about what happens when you don't give your home (or body) enough food—it starts to fall apart. The same thing happens when food is not properly digested and absorbed by the body; it can be toxic and contribute to inflammation in certain parts of the body that have been shown to increase cancer risk. That's why it's so important that we all try our best not only to eat healthily but also choose foods that are easy on digestion and won't cause discomfort later on down the road! We'll talk more about this later...
Conclusion
A little bit of weight gain is normal for most people, but when it becomes excessive, it can be detrimental to your overall health. The excess fat that has built up in your body can lead to serious health conditions like cancer, especially if you have had a family history of cancer.
We hope we’ve helped you understand the risk factors a little better—and that we’ve given you some encouragement to make changes for your health. The evidence is clear: maintaining a healthy weight through diet, physical activities, and other lifestyle changes throughout life is key to reducing your chances of developing certain types of cancer, and even in those with elevated risk, small changes can go a long way. Even if you weren’t always at a healthy weight, it’s never too late to start making changes for your health. And for some people with elevated cancer risk due to family history or a genetic mutation like BRCA1/2, these changes can make an even bigger difference.
