Nutrition News: Excess Weight is a Cancer Risk

Linda Kronheim, PA NEN

Do diet and body size impact chronic disease? The scientific evidence that these factors play a crucial role in the development of cancer and heart disease continues to accumulate. The table below briefly summarizes results from three recent reports, followed by more details about each of the studies and a brief discussion of the implications for nutrition educators.

 

Study

Body Size and Associated Risk

World Cancer Research Fund

Body fatness is associated with esophageal, pancreatic, colorectal, endometrial, kidney and breast cancer in postmenopausal women.

Million Women Study

Increasing BMI is associated with leukemia, multiple myeloma, non-Hodgkin’s lymphoma, esophageal, pancreatic, endometrial, kidney breast cancer in postmenopausal women, and colorectal cancer in premenopausal women.

Center for Disease Control (based on NHANES data)

Underweight/overweight is NOT associated with risk of death from cancer or cardiovascular disease.

Overweight IS associated with risk of death from diabetes and kidney disease.

Obesity IS associated with risk of death from cardiovascular disease and some cancers (colon, breast, esophageal, uterine, ovarian, kidney and pancreas).

 

The World Cancer Research Fund (WCRF) released a second report on dietary risk factors for cancer titled “Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective.” This report was the culmination of a massive review of over 7,000 published studies compiled by researchers from academic institutions across the United States, United Kingdom and Europe. A twenty-one-member expert panel evaluated the compiled evidence and developed recommendations for cancer prevention. Convincing evidence from the systematic literature review indicated that body fatness is associated with increased risk of a number of cancers. Based on this evidence, the expert panel’s recommendation on body size is to “be as lean as possible within the normal range of body weight.” The report also describes the evidence that particular dietary factors (such as types of food, preparation methods and general diet composition) contribute to the risk of specific cancers.

Results from the Million Women study, a prospective cohort study of women in the UK, indicated similar cancer risks associated with increasing BMI. This study also found a relationship between BMI and leukemia, multiple myeloma and non-Hodgkin’s lymphoma. In contrast to the WCRF results, a difference was found in colorectal cancer risk based on menopausal status; premenopausal women with higher BMI’s had increased risk, but postmenopausal women did not. The study design examines the relationship between body weight measured in middle-age women and their resulting short-term cancer risk: it does not speak to the role that body weight plays in cancer development.

A third recent study from the CDC clarifies the relationship between BMI and causes of death based on data from the NHANES surveys. These results indicate that being underweight or overweight does not increase the risk of dying from cancer or cardiovascular diseases. However, the risk of dying from diabetes and kidney disease is higher in overweight people. Obesity increases risk of death from both heart disease and cancer. In addition, the study found that cardiovascular disease was the primary contributor to excess death among the obese. This report examined only causes of death; risk of disease incidence was not considered.

Does informing consumers that excess pounds can increase their risk of developing cancer really motivate anyone to lose weight? According to a MedPage Today poll, 63 percent of respondents feel that attempting to scare people into weight loss is ineffective. Respondents shared their feelings that lack of motivation is typically not the issue for most people; rather, most individuals lack the knowledge or skills to maintain a healthy weight in environments that aggressively promote unhealthy eating. So how is this recent research relevant to nutrition educators? Perhaps one of the important findings that educators can emphasize is the importance of preventing excess weight gain. Obesity certainly increases health risk, but the evidence seems to suggest that simply being overweight by relatively few pounds may also pose health consequences. The WCRF report does not define weight into standard BMI categories, but chose the term “body fatness” to refer to the degree of body fatness across the whole range of BMIs. This decision highlights the importance for individuals to maintain the leanest body weight possible within the range of healthy weight. The WCRF expert panel concluded their report with recommendations for both public health and personal use. These recommendations may be useful in terms of helping clients understand practical ways to reduce their risk of cancer.

 

For full reports on these studies, please see:

Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective
http://www.dietandcancerreport.org/

Cause-Specific Excess Deaths Associated with Underweight, Overweight, and Obesity
http://jama.ama-assn.org/cgi/content/abstract/298/17/2028

Cancer Incidence and Mortality in Relation to Body Mass Index in the Million Women Study: Cohort Study
http://www.bmj.com/cgi/content/abstract/bmj.39367.495995.AEv1

Survey Report: Cancer Fear Won’t Curb Obesity (MedPage Today)
http://www.medpagetoday.com/Surveys/Surveys/dh/7318