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The weight of obesity
What’s the connection?
Will losing weight lower your risk?

How much weight is too much?
How much weight is too much?

Physicians assess overweight and obesity with a formula called the body mass index (BMI), which is a measure of your weight in relation to your height. You can find your BMI by checking the BMI charts or using the calculator tool from the National Heart, Lung and Blood Institute at

A BMI between 25 and 30 is considered overweight; 30 and higher is obese. If you’re in either category, your risk of many diseases, including cancer, goes up.

By now, most of us are aware that too much weight is unhealthy. And you may already know that extra pounds increase your risk for diabetes, heart disease and stroke. But did you know that being overweight is also linked to cancer?

It’s true. Cancers of the colon, breast (in postmenopausal women), uterus, kidney and esophagus are clearly associated with obesity, says the National Cancer Institute (NCI). In fact, obesity may account for up to 30 percent of these cancers. Some studies have found connections between obesity and cancers of the gallbladder, ovaries and pancreas as well. In all, 14 percent of cancer deaths in men and 20 percent of cancer deaths in women may be due to overweight and obesity.

What’s the connection?

Scientists aren’t exactly sure how obesity increases cancer risk, but they have a few theories. One possibility is that excess weight may affect insulin, hormones (like estrogen, progesterone and androgens) and other body chemicals that play a role in cancer risk. The connections may be different for different types of cancer.

There may also be a link between where fat is stored and cancer risk. For example, women with a large amount of abdominal fat have a greater breast cancer risk than those who carry fat in their hips, buttocks and legs. Abdominal obesity may be more important in colon cancer risk as well.

Will losing weight lower your risk?

In a word, yes. Even a loss of only 5 percent to 10 percent of total weight can improve your odds, the NCI reports. That’s just 10 to 20 pounds for a 200-pound adult.

To help lower cancer risk, the American Cancer Society recently released new guidelines that focus on the following nutrition and exercise habits:

  • Maintain a healthy weight throughout life. If overweight, take steps to lose excess pounds.
  • Adopt a physically active lifestyle. Aim for at least 30 minutes of moderate to vigorous activity in addition to daily activities.
  • Eat a healthy diet, with an emphasis on plant foods like fruits, vegetables and whole grains.
  • Limit alcohol to no more than two drinks a day for men and one for women—if you drink it at all.

Talk to your healthcare provider about helping you make the lifestyle changes you need to lower your risk for disease—even cancer.