Many people think that whether or not you get cancer is just luck of the draw. Or, that your chances are determined by genes you inherit from your parents.
While there is some randomness to who develops cancer, and genes are important, a new awareness survey suggests most people don’t know about lifestyle and health characteristics that affect your risk for cancer. Several of these can be reversed.
We’ve known for many years that being overweight or obese increases risk for several types of cancer, including cancers of the colon, rectum, endometrium, liver, kidney, breast (in postmenopausal women), gallbladder, pancreas, and some parts of the stomach, ovary, and esophagus. Obesity also increases risk for developing advanced prostate cancer, the most dangerous stage of this cancer. Some newer studies suggest that obesity also increases risk for thyroid cancer and for some cancers of the blood, lymph, and nervous systems.
The good news is that some of these so-called “obesity-related” cancers can be prevented. That is, it’s never too late to reduce your risk for these cancers. When researchers followed people who intentionally lost weight, they discovered that weight loss reduced risk for breast and other cancers, particularly in women. There is still more research to do—more studies are needed to confirm these findings, and to look further at weight loss in men.
“The good news is that some of these so-called “obesity-related” cancers can be prevented. That is, it’s never too late to reduce your risk for these cancers.”
In an ideal world, researchers would test the effect of weight loss on cancer occurrence in a clinical trial, the gold standard in medical research.
However, that kind of study would require thousands of people in a weight loss program being followed for many years. Until such a study can be conducted, we have to rely on other sources of information.
Fortunately, there’s strong evidence of the benefits of weight loss on biological factors that predispose people to cancer.
In a series of clinical studies at the Fred Hutchinson Cancer Research Center, we assigned people by chance to weight loss diets, exercise programs, or control groups. We’ve found that reducing weight through either diet or exercise significantly lowers the following cancer risk factors:
• Estrogens and testosterone, which are risk factors for breast and endometrial cancers.
• Inflammation-related proteins, which increase risk for colon and other cancers.
• Proteins that control growth of blood vessels. By lowering these, tumors would have less nourishment to grow.
• Insulin, glucose, and related metabolic factors, which if left unchecked, cause overgrowth of many cells including tumor cells.
• Oxidative stress, which results in normal cells being attacked, possibly inciting a cell to turn cancerous.
• Proteins made in fat tissue, which have been associated with increased cancer risk.
The amount of weight needed was not high—losing just 5 percent of starting weight had a big effect. So, for a person weighing 200 pounds at the start of the study, losing 10 pounds produced a beneficial effect.
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Our diet programs were simple and easy to adopt. We asked our study participants to count calories and reduce fat intake. We gave them a lot of help in doing this, in the form of group classes, individual meetings with expert nutritionists, and advice on changing their lifestyles to help them lose weight.
We found that people who regularly wrote down everything they ate, prepared their own meals, and didn’t skip meals lost the greatest amount of weight. We found that exercise by itself produces little weight loss, but that regular, moderate-intensity aerobic exercise provided additional weight loss benefits when added to the diet program.
It’s never too late to make health-improving changes, including decreasing your risk for cancer. In our studies, people aged 60 years and older often had greater effects from weight loss on their cancer risk factors. And people who had previously lost and regained pounds did just as well as those who had never lost weight in the past.
“It’s never too late to make health-improving changes, including decreasing your risk for cancer.”
So if you’ve gained some unwanted pounds over the years, reducing your risk for cancer may be an additional incentive to make lifestyle changes to lose weight.
Anne McTiernan, MD, PhD, conducts research on the effects of diet, exercise, and weight loss on cancer and health. Currently, she is faculty at the Fred Hutchinson Cancer Research Center and professor at the University of Washington Schools of Public Health and Medicine in Seattle, Washington. She is the author of Starved: A Nutrition Doctor’s Journey from Empty to Full. (Central Recovery Press, November 2016)