Risk and Prevention  /   Exercise, Body Weight and Cancer

Studies most strongly associate being overweight and/or obese with a higher risk of breast (postmenopausal women), colorectal, endometrial, esophagus and renal cell cancers. Evidence points to obesity as a cause for gall bladder and pancreas cancer as well. Experts estimate that 14% of cancer deaths in men and 20% of cancer deaths in women are caused by obesity. It is likely that the mechanism for this risk is different for each cancer. Researchers believe that hormones that are produced at higher levels in the presence of extra weight, including insulin, leptin and estrogen, are one cause. For example, fat cells are the primary source of estrogen in postmenopausal women, thus more fat cells may lead to higher risk of breast cancer in overweight/obese women.

Experts measure body weight using body mass index or BMI. BMI is a measure of body fat based on a person's height and weight. This is a good place to start to evaluate your body weight and see where you fall on the chart, which classifies your BMI as underweight, healthy, overweight and obese.

A healthy diet, combined with regular physical activity and maintaining a healthy weight has been shown to reduce cancer risk. This triangle is thought to be the second most important step, after not smoking, to preventing cancer. A few studies have found that losing weight can help decrease the risk of weight-related cancers. The most convincing evidence for losing weight as a risk reduction technique comes from studies of people who have undergone bariatric (weight loss) surgery. In a sample of U.S. bariatric surgery patients, cancer death rates were 38% lower than people who were obese and did not undergo surgery.

Losing weight is no easy task. It takes a strong commitment to making big lifestyle changes. Seek support from friends, family, your healthcare providers and weight loss programs. Investigate websites or applications (Apps) to track progress and motivate you. Get started by learning more at the American Cancer Society and LIVESTRONG.

Resources to learn more about how diet, physical activity and weight are related to cancer

• American Institute for Cancer Research
• Take Control of Your Weight at the American Cancer Society website.
• Eat Healthy and Get Active at the American Cancer Society website.
• American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention.
• Dietary Guidelines for Americans, 2010 from the USDA.
• The US Department of Health & Human Services 2008 Physical Activity Guidelines for Americans.
• NIH AARP Diet & Health Study: a study developed at the National Cancer Institute of the National Institutes of Health to improve our understanding of the relationship between diet and health.
• The European Prospective Investigation into Cancer & Nutrition (EPIC): A large study by the International Agency for Research on Cancer investigating the relationships between diet, nutritional status, lifestyle and environmental factors and the incidence of cancer and other chronic diseases.