Being Well

Understanding Obesity and Cancer Risk

Being overweight or obese could increase your risk of multiple types of cancer. Obesity is a key risk factor for developing many types of cancer, including breast, colon, rectal, prostate and esophageal.

Being overweight or obese could increase your risk of developing many types of cancer according to research. The American Cancer Society estimates that excess body weight contributed to as many as one in five cancer-related deaths, and study in The Lancet Oncology estimates that 3 to 6 percent of new cancer cases worldwide could be attributed to high body mass index (BMI). Carrying excess weight has been shown to increase your risk of esophageal, colon, bowel, bladder, breast and ovarian cancers, in particular. Yet, the reason why isn’t so straightforward.

The Obesity and Cancer Link

BMI, which is a ratio of your height to weight, is a good starting point for determining whether you’re at a healthy weight. You can figure out your own BMI number by taking advantage of an online BMI calculator that will do the math for you. Your resulting number will then fall into a certain range that determines if you have a healthy weight. Someone in a healthy weight range has a BMI of 19 to 25. A BMI of 26 to 30 is overweight, and a BMI over 30 is considered obese.

To put that in perspective, a woman who is 5 feet, 5 inches tall can have a healthy weight of anywhere from 112 pounds to 153 pounds. Science Daily reports that researchers at the Medical University of Vienna found that people with a BMI of 30 and above face a much higher risk of developing cancer than people with a lower BMI.

Although BMI is a decent place to start, it doesn’t tell the whole story: BMI calculations don’t differentiate between muscle mass and fat. To this point, the Vienna research suggested that abdominal girth and belly fat might be more accurate predictors of cancer risk. Fat tissue changes the balance of key hormones in your body, which can help drive tumor growth.

The time in your life that you carried extra weight may also make a difference. The American Cancer Society suggests that having excess weight early in life, in childhood or adolescence, puts you at higher risk than gaining weight as an adult.

But What’s the Connection?

Researchers don’t fully understand the link between obesity and cancer. If you’re carrying excess weight, it’s still not clear exactly what happens in your body to increase your risk. It does seem, however, that your body undergoes many changes because of fatty tissue. These include:

  • Hormone changes: Fatty tissue produces certain hormones and changes the balance of hormones in your body, such as causing androgen precursors to be converted into estrogen, which can fuel the growth of tumors. Other changes in your body can “turn off” hormones that limit tumor growth.
  • Immune changes and inflammation: The American Cancer Society says that more body fat may cause immune system shifts and create more inflammation in your body, preventing your body’s ability to fight illness.


Maintaining a healthy weight is a good way to lower your risk of developing cancer. Helping your kids develop healthy eating habits and stay physically active will help lower their lifetime risk of cancer, as well.

While it benefits you to maintain a healthy weight throughout your lifetime, it’s never too late to start losing weight by eating well and exercising often if you’re carrying extra pounds. The best way to lose weight is through a healthy diet, consisting of fruits, vegetables and lean protein, along with regular exercise. Follow a low-fat diet. This doesn’t mean you have to buy all low-fat products, but rather focus on balancing your diet. Limit red meat and milkshakes or other high-fat snacks, for example. Additionally, boost your fiber intake. Eating a high-fiber diet, particularly from fruits and vegetables, can lower your risk of breast cancer.

Other steps you can take to lower your risk include avoiding unhealthy habits that also contribute to cancer, such as excess alcohol consumption and smoking. Whatever you decide, sustaining a healthy lifestyle and seeing your doctor regularly are the best things you can do in terms of cancer prevention.

Consider visiting a nutritionist or talk with your primary care provider about lifestyle changes you can make to lower your risk of cancer.

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Patricia Chaney
Patricia Chaney