Obesity, Nutrition, Physical Activity, and Cancer: What's the Scientific Connection?

February 14, 2017

For the majority of Americans who do not use tobacco products, weight management, good nutrition, and physical activity are the greatest modifiable determinants of cancer risk1.  Scientific evidence suggests that approximately one fifth of the cancer cases expected to occur in the United States this year are due to excess weight, poor nutrition, and physical inactivity2.

Currently, 37 percent of adults and 17 percent of youth (ages 2-19) are obese3. Roughly 71 percent of adults are either overweight or obese4,5.  Adult obesity more than doubled between 1976-1980 and 1999-20006, but since then has increased only slightly among men7.  Between the early 1970s and the early 2000s, youth obesity more than tripled8, but has largely leveled off.  Although obesity rates are no longer increasing dramatically, they are still high, and existing levels of obesity are causing a significant burden of chronic disease. Large racial, ethnic, and geographic disparities in obesity rates exist across all age groups.9,10 

Excess body weight is clearly associated with an increased risk of cancer development and recurrence, as well as decreased risk of survival11, for many cancers. Weight control reduces the risk of cancers of the female breast (postmenopausal)12, colon and rectum13, uterus14, kidney15, adenocarcinoma of the esophagus16, pancreas17, ovary18, liver, gastric cardia, gall bladder19,  thyroid, meningioma, and multiple myeloma.20

The reasons for the biological link between excess body weight and cancer are complex.  The relationship is likely related to effects on immune function and inflammation, levels and metabolism of insulin and other hormones, factors related to cell growth, and proteins that make hormones more or less available.20,21  

Regular physical activity reduces cancer risk both directly and by helping to maintain a healthy body weight. In fact, a recent study found that those with high levels of leisure-time physical activity had lower risk of 13 types of cancer, including cancers of the esophagus, liver, lung, kidney, stomach, endometrium, colon, rectum, head and neck, bladder, and breast, and myeloid leukemia and myeloma23.  The American Cancer Society (ACS) and other experts recommend that adults engage in at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity activity each week and that children and adolescents engage in at least 1 hour of moderate- or vigorous-intensity activity each day, with vigorous intensity activity at least 3 days per week24,25.  Physical activity after a cancer diagnosis has been shown to improve physical functioning, quality of life, and fatigue26 and may also reduce the risk of recurrence.27

ACS Guidelines recommend consuming a healthy diet, with an emphasis on plant foods. The Guidelines emphasize portion control for weight management, limiting red and processed meats, eating at least 2.5 cups of fruits and vegetables daily, reducing consumption of sugar-sweetened beverages, choosing whole grains over refined grain products, and limiting alcohol consumption to no more than one drink per day for women and two for men.

Helping Americans to eat healthy, be physically active, and manage their weight saves lives. Several recent studies have found that nonsmoking adults who followed cancer prevention guidelines for weight control, diet, physical activity, and alcohol had a lower risk of dying from cancer28, cardiovascular disease, and all causes.29

 


References

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2 American Cancer Society. Cancer Facts & Figures 2017.  Atlanta: American Cancer Society, 2017.
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