Thomas Jefferson University
Jefferson Digital Commons
Department of Family & Community Medicine
Department of Family & Community Medicine
Obesity and Cancer
Rickie Brawer, PhD, MPH
Thomas Jefferson University
Nancy Brisbon, MD
Thomas Jefferson University
James Plumb, MD
Thomas Jefferson University, email@example.com
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Brawer, PhD, MPH, Rickie; Brisbon, MD, Nancy; and Plumb, MD, James, "Obesity and Cancer"
(2009).Department of Family & Community Medicine Faculty Papers.Paper 17.
Brawer R, Brisbon N, Plumb J. Obesity and cancer. Primary Care - Clinics in Office
Practice. 2009; 36(3):509-531.
Obesity has become the second leading preventable cause of disease and death in the
United States, trailing only tobacco use. Weight control, dietary choices, and levels of physical
activity are important modifiable determinants of cancer risk. If multi-factorial approaches to
prevention and management are not implemented, obesity will likely become the leading
modifiable cause of death in the coming years. Physicians have a key role in integrating these
approaches into clinical care and advocating for systemic prevention efforts. This article
provides: 1) an introduction to the epidemiology and magnitude of childhood and adult obesity;
2) the relationship of overweight/obesity to cancer and other chronic diseases, 3) potential
mechanisms postulated to explain these relationships; 4) a review of recommended obesity
treatment and assessment guidelines for adults, adolescents and children: 5) multi-level
prevention strategies, and; 6) an approach to obesity management in adults utilizing the Chronic
Epidemiology and Problem Magnitude
Overweight in adults is defined as a body mass index (BMI) of 25 to 29.9 kg/m2, and
obesity as a BMI of > 30 kg/m2. In children and adolescents, obesity is defined as a level that is
>95 percentile, replacing the older terminology of “overweight”, and overweight as a BMI in the
85th to 94th percentile, replacing “at risk of overweight”.
The increasing prevalence of obesity in the United States is well known and is now
considered of epidemic proportion. Given the current trends in weight gain, nearly 75% of adults
are predicted to be overweight by 2015. In 1980, only15% of the adult population of the U.S.
was classified as obese. The National Health and Nutrition Examination Survey (NHANES)
data from 2003-04 show that 66% of the adult population ages 20-74 is overweight (BMI >25)
and almost 33% is obese (BMI >30). (1) The trend in obesity among youth is dramatic with an
increase from approximately 5% in 1963-1970 to 17% in 2003-2004, with more than 25 million
children and youth now obese or overweight. (1)
According to F as in Fat Report: How Obesity Policies are Failing in America (2), the
2008 follow-up analysis of the 2004-2006 Behavioral Risk Factor Surveillance Survey (BRFSS)
conducted by the Trust For America’s Health and the Robert Wood Johnson Foundation, obesity
rates have continued to rise in 31 states and have not dropped in a single state. The U.S.
Department of Health and Human Services (DHHS) in Healthy People 2010, the National
Objectives for Improving Health, set a national goal to reduce adult obesity levels to fifteen
percent in every state by the year 2010; for children and adolescents, the goal is five percent or
Race, ethnicity and socioeconomic status disproportionately affect the development of
obesity. A systematic meta regression analysis conducted by Wang & Bedouin (4) using
NHANES and BRFSS data as well as the Youth Risk Behavior Surveillance System (YRBSS)
and the National Longitudinal Survey of Adolescent Health found that some minorities and low
socioeconomic (SES) groups such as Non-Hispanic Black women and children, Mexican-
American women and children, low SES Black men, white women and children, and Native
Americans and Pacific Islanders are disproportionately affected. According to Wang and
“The NHANES data show a dramatic increase in the prevalence of overweight
and obesity across all populations and a declining disparity of obesity across SES groups
over the past decade. This finding indicates that individual characteristics are not the
dominant factor to which the rising obesity epidemic is ascribed, i.e., social and
environmental factors might have a more profound effect in influencing individuals’
body weight status than do individual characteristics such as SES” (4 - page 19).
The consequences of obesity encompass a variety of physical, social and economic
factors affecting individuals and society. The adverse health effects of obesity have created
enormous direct and indirect health care costs. According to 2002 data from the U.S. Department
of Health and Human Services, the economic costs related to obesity were estimated at over 117
billion dollars. A study examining the relationships of BMI in young adulthood and middle age
to subsequent health care expenditure at ages 65 years and older found average annual and
cumulative Medicare charges were significantly higher for individuals, both men and women,
with a higher baseline BMI (5). Wang and Dietz estimate that hospital costs of treating children
for obesity-associated conditions rose from $35 million to $127 million from 1979-81 to 1997-99
(6). Having a BMI> 35 is an independent risk factor for frequent utilization of adult visits to
Family Medicine practices (7).
There is strong evidence that weight loss reduces risk of further complications for
persons with diabetes and cardiovascular disease, and improves blood pressure, and blood
glucose and cholesterol levels.
Well-controlled clinical trials have demonstrated that lifestyle modification can decrease
blood pressure (8, 9), prevent or forestall development of type 2 diabetes (10, 11) and reduce
other risk factors for cardiovascular disease (12, 13). The health benefits of weight loss and
increased physical activity are well established (14). Modest weight loss, of 5-10%, is associated
with significant improvement in blood pressure, lipoprotein profile, glucose tolerance and insulin
sensitivity (15). Physical activity has similar benefits on cardiovascular risk factors. The inverse
association between physical activity and cardiovascular disease risk is mediated in substantial
part by known risk factors, particularly inflammatory/hemostatic factors and blood pressure (16).
Obesity and Cancer
Many factors that contribute to cancer deaths are preventable. It has been estimated that
from 50-70% of cancer deaths are related to preventable risk behaviors; 30% of cancer deaths
can be attributed to tobacco use and more than 30% to poor nutrition (17). There is also
expanding evidence of the role of obesity in cancer development, treatment and survival. A
recent review and meta-analysis of prospective observational studies showed an association
between increased BMI and certain cancers by sex. In men, increased BMI was strongly
associated with esophageal adenocarcinoma, thyroid, colon and renal cancers. Weaker
associations were seen between increased BMI and malignant melanoma, multiple myeloma,
rectal cancer, leukemia and non Hodgkin’s lymphoma in men. In women, strong associations
were seen between endometrial, gallbladder, renal cancers and esophageal adenocarcinoma.
Weaker associations with women’s increased BMI were seen for leukemia, thyroid, post
menopausal breast, pancreas, and colon cancers and non Hodgkin’s lymphoma (18). Further, for
gynecologic cancers, another review found an adverse affect of obesity on endometrial cancer
survival (19). Calle, Rodriquez, Thurmond and Thun, (20) prospectively studied a population of
more than 900,000 adults who were free of cancer at enrollment in 1982, where there were
57,145 deaths form cancer during 16 years of follow-up. The authors controlled for risk factors
other than weight in a multivariate proportional hazards models. In both men and women, body-
mass index was significantly associated with higher rates of death due to cancer of the
esophagus, colon and rectum, liver, gallbladder, pancreas, and kidney: the same was true for
death due to non-Hodgkin’s lymphoma and multiple myeloma. Significant trends for increasing
risk with higher body-mass index values were observed for death from cancers of the stomach
and prostate in men and for death from cancers of the breast, uterus, cervix, and ovary in women.
On the basis of associations observed in this study, the authors estimated that current patterns of
overweight and obesity in the United States could account for 14 percent of all deaths from
cancer in men and 20 percent of those in women.
Researchers are considering the biochemical/physiologic implications of obesity in the
development of chronic diseases and cancer. In the development of atherosclerosis and diabetes,
obesity has been studied as a form of epidemic inflammation that predisposes the body to other
forms of epidemic inflammation known to be involved in these disease states (21). For cancer,
the relationships are evolving and may be site and gender specific. Multiple mechanisms being
studied include chronic hyperinsulinemia/insulin resistance which is believed to create an
environment favorable for tumor formation via changes in the availability of insulin growth
factor (IGF) – possibly key in the development of colon and prostate cancers. In postmenopausal
breast cancer, adipose tissue enzymatic activity may result in high rates of conversion of
precursors to estrogen which increases endometrial cell proliferation and inhibits apoptosis. An
interaction between estrogen and IGF may play a role in the development of endometrial cancer
as well. The role of adipokines is also being explored. Adiponectin, secreted primarily by
visceral adipose tissue is antiangiogenic and anti-inflammatory in animals. Adiponectin levels
correlate inversely with BMI and hyperinsulinemia, and have been reported to have associations
reading food labels, healthy meal planning, supermarket tours, shopping on a budget, cooking
healthy for a family demonstrations, healthy snacking, dining out, healthier shopping at corner
stores, and integrating physical activity into daily life. A digital scale is provided at each class
for those wishing to weigh themselves. Each participant in the program is given a pedometer to
raise awareness about and encourage physical activity (79). The Community Health Educator
also monitors participant attendance, retention and completion rates (daily attendance and
follow-up with “no-shows”); supports participants in goal-setting and implementing personal
action plans; catalogues community based nutrition and physical activity resources in targeted
neighborhoods and prepare a neighborhood resource guide; coordinates with the Lifestyle
Counselor; refers participants to community programs that can augment lifestyle changes; and
performs pre/post intervention data collection in collaboration with the Lifestyle Counselor.
A summary of the data for the first 151 CCIP participants enrolled between October 2006 and
June 2007 (i.e., those for who at least one year has elapsed since enrollment) follows.
Participants were enrolled at two sites (90 at JFMA and 61 at HC6), and were between 18 and 45
years of age (mean = 34) and mostly female. Physical activity data both at baseline and at 9
months were available for 27 participants. Despite small changes in physical activity and diet,
among the 27 participants with height and weight data at baseline and 9 months, weight
decreased by an average of about 11 lbs (p = 0.002). Average BMI also decreased from 40.2
kg/m2 at baseline to 38.4 kg/m2 at 9 months, corresponding to a mean absolute decrease of 1.8
kg/m2 (p = 0.002) and a mean relative decrease of 4% (p = 0.003). Enrollment and evaluation
continues. Currently, 545 individuals have been enrolled.
SUMMARY – The social, medical and economic consequences of the obesity epidemic are
enormous. An ecological approach to prevention and a systematic clinical and counseling
approach, based on current guidelines, will be required to reverse the growing epidemic.
Providers can integrate these approaches into daily practice by identifying, assessing, counseling
and treating using a patient-centered approach that is based on, and tailored to a patient’s
readiness and motivation to change. Clinicians can advocate for systems and policy changes to
support adult and youth overweight prevention, and management. They can support changes in
school policies such as health beverages and food choices, and required physical activity. They
can encourage modifications in the built environment that support physical activity, and can
advocate for healthy, affordable food that is accessible to all their patients. Lastly, clinicians can
support legislation that supports healthier lifestyles and requires insurers to support obesity
related counseling and education.
Acknowledgments: Work on this manuscript has been supported in part under a grant with the
Pennsylvania Department of Health. The Department specifically disclaims responsibility for
any analyses, interpretation, or conclusions.
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