general oncology from devita presentation

1. 12 Obesity and Physical Activity
Justin C. Brown, Jeffrey A. Meyerhardt, and Jennifer A. Ligibel
INTRODUCTION
There is growing interest in the oncology community to understand how obesity and physical activity may relate
to cancer risk and outcomes.1 This interest is synergized by the curiosity of patients to understand how modifiable
health behaviors may influence their individual risk of developing or dying from cancer.2
Worldwide, one-fifth of the adult population—approximately 640 million people—are obese.3 Obesity,
considered by many as a 21st-century epidemic, is a disproportionate body weight for height.4 Obesity is
associated with an increased risk of developing and dying from several major illnesses, including cardiovascular
disease, type 2 diabetes, and cancer. It is predicted that in the year 2020, the United States will spend $28 billion
treating obesity-related illnesses; this estimate is projected to increase to $66 billion by the year 2030.5 Given the
rising prevalence of obesity in the U.S. population coupled with declining smoking rates, obesity is quickly
overtaking smoking as the leading preventable cause of cancer.6 It is estimated that 20% of new cancer cases and
17% of cancer-related deaths are attributable to obesity.7 However, three-quarters of the adult population remain
unaware of the relationship between obesity and cancer.8
In addition to the relationship between obesity and cancer risk, other energy balance factors have also been
linked to cancer risk. Physical inactivity is associated with an increased risk of developing and dying from several
major illnesses, including cardiovascular disease, type 2 diabetes, and cancer. It is estimated that 10% of all new
cancer cases and 9% of cancer-related deaths are attributable to physical inactivity.9,10 Conservatively appraised,
physical inactivity was responsible for $24.7 billion in health-care spending in the United States in 2013.11
Despite the observation that 1 minute of moderate-intensity physical activity provides 7 minutes of additional
life,12 less than one-fifth of the adult population are aware that national guidelines recommend participation in
physical activity.13
This chapter is divided into three discrete sections. The first section focuses on obesity; the second section
focuses on physical activity; and the third section focuses on mechanistic data, sedentary behavior, clinical
practice guidelines and efforts to increase awareness of these areas within the oncology community. This chapter
is not an exhaustive review of all data on energy balance. Rather, this chapter serves as a primer for oncology
professionals to begin to understand the current state of the science on obesity and physical activity.
OBESITY
Body mass index (BMI) is used to quantify body weight for height by indexing body weight (in kilograms) by the
square of height (in meters). Although there is debate on the precise definition of obesity, the World Health
Organization categorizes obesity as a BMI ≥30 kg/m2.14
OBESITY AND CANCER RISK
In 2003, a landmark study of 900,000 U.S. adults demonstrated that obese men and women were up to 52% and
62% more likely to develop and die from cancer, as compared to their normal-weight counterparts, respectively.15
Following this seminal work, dozens of additional case-control and cohort studies have evaluated the relationship
between body weight and cancer risk. In 2016, the International Agency for Research on Cancer (IARC)
convened a working group of 21 independent international experts to assess the effects of obesity on cancer risk.
This working group systematically reviewed more than 1,000 studies that investigated the relationship between

2. Dr. AVR @ TMH
obesity and cancer risk and determined there was sufficient evidence to conclude that obesity is associated with an
increased risk of developing 13 different types of cancer (Table 12.1).16 The increased risk of malignancy
associated with obesity is strongest in endometrial cancer (relative risk, 7.1). Other cancers in which the link
between obesity and risk is particularly strong include esophageal adenocarcinoma, gastric cardia, liver, renal cell,
and multiple myeloma (relative risks, ≥1.5). Cancers that are not associated with obesity are often cancers for
which smoking is a strong risk factor, as smoking and obesity are inversely correlated.17
OBESITY AND CANCER OUTCOMES
In addition to the relationship between obesity and cancer risk, evidence suggests that individuals who are obese
at the time of cancer diagnosis are at increased risk of cancer recurrence and mortality, compared to individuals of
normal body weight. Most of the evidence demonstrating a relationship between obesity and cancer outcomes that
have been corroborated by meta-analyses are in individuals with cancers of the breast, colon and rectum, prostate,
and endometrium (Table 12.2).
In breast cancer, obesity is associated with an increased risk of breast cancer–specific and all-cause mortality.
In a recent meta-analysis including 82 individual reports looking at the relationship between body weight at
diagnosis and cancer outcomes, obese women had a 35% higher risk of breast cancer–specific mortality and a
41% higher risk of all-cause mortality as compared to women with a BMI in the normal range. This relationship
between obesity and poor outcomes was seen in both pre- and postmenopausal women.18 Although not included
in the meta-analysis, several reports suggest that weight gain after diagnosis may be associated with an increased
risk of breast cancer recurrence and mortality.19 In colorectal cancer, obesity is associated with an increased risk
of cancer recurrence, and colorectal cancer–specific and all-cause mortality, although there is some suggestion
that patients with BMI in the overweight range (BMI, 25.0 to 29.9 kg/m2) are reported to have superior outcomes
compared with those who are of a normal weight.20 In prostate cancer, obesity is associated with an increased risk
of biochemical recurrence and prostate cancer–specific mortality after radical prostatectomy.21 Weight gain after
diagnosis may be associated with an increased risk of prostate cancer recurrence.22 In endometrial cancer, obesity
is associated with an increased risk of all-cause mortality, particularly among women with morbid obesity (BMI
≥40 kg/m2).23 There is emerging evidence that obesity is associated with outcomes in other cancers.24
TABLE 12.1
Strength of the Evidence for a Cancer-Preventive Effect of the Absence of Excess Adiposity,
According to Cancer Site or Type
Cancer Site or Type Strength of the Evidence in Humansa
Relative Risk of the Highest BMI
Category Evaluated versus Normal BMI
(95% CI)b
Esophagus: adenocarcinoma Sufficient 4.8 (3.0–7.7)
Gastric cardia Sufficient 1.8 (1.3–2.5)
Colon and rectum Sufficient 1.3 (1.3–1.4)
Liver Sufficient 1.8 (1.6–2.1)
Gallbladder Sufficient 1.3 (1.2–1.4)
Pancreas Sufficient 1.5 (1.2–1.8)
Breast: postmenopausal Sufficient 1.1 (1.1–1.2)c
Corpus uteri Sufficient 7.1 (6.3–8.1)
Ovary Sufficient 1.1 (1.1–1.2)
Kidney: renal cell Sufficient 1.8 (1.7–1.9)
Meningioma Sufficient 1.5 (1.3–1.8)
Thyroid Sufficient 1.1 (1.0–1.1)c
Multiple myeloma Sufficient 1.5 (1.2–2.0)
Male breast cancer Limited NA

3. Diffuse large B-cell lymphoma Limited NA
Esophagus: squamous cell carcinoma Limited NA
Gastric noncardia Inadequate NA
Extrahepatic biliary tract Inadequate NA
Lung Inadequate NA
Skin: cutaneous melanoma Inadequate NA
Testis Inadequate NA
Urinary bladder Inadequate NA
Brain or spinal cord: glioma Inadequate NA
aSufficient evidence indicates that a preventive association has been observed in studies in which chance, bias, and confounding
could be ruled out with confidence. Limited evidence indicates that a reduced risk of cancer is associated with the intervention for
which a preventive effect is considered credible by the working group, but chance, bias, or confounding could not be ruled out with
confidence. Inadequate evidence indicates that the available studies are not of sufficient quality, consistency, or statistical power to
permit a conclusion regarding the presence or absence of a cancer-preventive effect of the intervention.
bFor cancer sites with sufficient evidence, the relative risk reported in the most recent or comprehensive meta-analysis or pooled
analysis is presented. The evaluation in the previous column is based on the entire body of data available at the time of the meeting
(April 5 to 12, 2016) and reviewed by the working group and not solely on the relative risk presented in this column. Normal BMI is
defined as 18.5 to 24.9.
cShown is the relative risk per 5 BMI units.
BMI, body mass index; CI, confidence interval; NA, not applicable.
From Lauby-Secretan B, Scoccianti C, Loomis D, et al. Body fatness and cancer—viewpoint of the IARC working group. N Engl J
Med 2016;375(8):764–798. Copyright (2017) Massachusetts Medical Society. Reprinted with permission from Massachusetts
Medical Society.
There is also growing interest in understanding the associations between body composition, an indication of the
relative proportions of lean mass and fat mass, and cancer outcomes.25 Excess intra-abdominal adiposity and low
muscle at the time of diagnosis may be associated with poor outcome in a variety of cancer sites.26,27 These data
provide complementary evidence to further strengthen the observation that obesity is associated with outcomes in
cancer.
OBESITY AND CANCER TREATMENT–RELATED COMPLICATIONS
Obesity is associated with an increased risk of complications from cancer-directed therapy.6 For example, among
2,258 patients undergoing intra-abdominal cancer surgery, obesity was associated with an increased risk of
postoperative 30-day morbidity (23.1% in normal weight versus 29.9% in obese; P = .002).28 Obesity can impact
type of surgery for certain cancers. For example, in rectal cancer, obese patients are more likely to undergo
abdominoperineal resection and consequently have a permanent colostomy.29 There is also evidence that obesity
may influence treatment tolerance. In breast cancer, obesity is associated with a higher risk of cardiotoxicity from
anthracycline and trastuzumab therapies,30 persistent chemotherapy-induced peripheral neuropathy,31 treatment-
related lymphedema,32 and poorer wound healing.33 Other obesity-related complications continue to emerge.34
INTERVENTIONS
Current public health guidelines encourage the avoidance of excess weight gain, and for those who are currently
overweight or obese, modest weight loss is encouraged to reduce the risk of comorbidities and other cancers.35
However, it is not yet known if intentional weight loss reduces the risk of developing malignancy or prevents
disease recurrence and cancer-specific mortality among individuals diagnosed with early-stage cancer. The best
evidence to date that weight loss could reduce the risk of malignancy comes from the bariatric surgery literature,
where individuals who undergo surgery have a 27% to 59% lower risk of developing cancer, as compared to
weight- and age-matched controls who do not undergo surgery.36 The benefits of bariatric surgery are particularly
strong for preventing obesity-related cancers, such as that of the breast and endometrium, where the average risk
reduction is 38% (P < .0001).36 One observational study also suggested that intentional weight loss achieved
through diet and exercise was associated with a 66% lower risk of developing endometrial cancer, although this
needs further validation in other studies.37

4. Dr. AVR @ TMH
TABLE 12.2
Review of Key Meta-analyses Linking States of Obesity to Poor Outcomes in Cancer
Survivors
Cancer
Site
Author,
Year,
Reference
No. of
Studies
Sample
Size Exposure Outcome Results Notes
Breast Chan et
al., 201418
82 213,075 Obese
(BMI ≥30
kg/m2) vs.
normal
weight
(BMI
18.5–24.9
kg/m2
)
All-cause
mortality;
breast
cancer–
specific
mortality
HR, 1.41 (95% CI,
1.29–1.53) for all-
cause mortality
HR, 1.35 (95% CI,
1.24–1.47) for breast
cancer–specific
mortality
Obesity associated
with poorer prognosis
in both pre- and
postmenopausal
breast cancer
Colorectal Doleman
et al.,
201465
18 60,346 Obese
(BMI ≥30
kg/m2) vs.
normal
weight
(BMI
18.5–24.9
kg/m2)
All-cause
mortality;
colorectal
cancer–
specific
mortality;
disease
recurrence
RR, 1.14 (95% CI,
1.07–1.21) for all-
cause mortality
RR, 1.14 (95% CI,
1.05–1.24) for
colorectal cancer–
specific mortality
RR, 1.07 (95% CI,
1.02–1.13) for disease
recurrence
Results were
consistent among men
and women, colon and
rectal primary cancers,
and timing of BMI
measurement (before
diagnosis vs. at
diagnosis).
Prostate Cao and
Ma,
201121
6 18,203 Each 5-
kg/m2
increase
in BMI
Prostate
cancer–
specific
mortality;
biochemical
recurrence
RR, 1.20 (95% CI,
0.99–1.46) for
prostate cancer–
specific mortality
RR, 1.21 (95% CI,
1.11–1.31) for
biochemical
recurrence
Results were
consistent across
countries, timing of
BMI measure (before
vs. at diagnosis), and
type of BMI measure
(self-report vs.
objectively measured).
Results stronger in
men treated with
external beam
radiation
Endometrial Secord et
al., 201623
18 665,694 Each 10%
increase
in BMI,
compared
to BMI of
25 kg/m2
All-cause
mortality
Each 10% increase in
BMI associated with
9.2% in risk of
mortality
Results were strongest
among women with
BMI ≥40 kg/m2 (66%
increased risk of
death) compared to
women with BMI <25
kg/m2.
BMI, body mass index; HR, hazard ratio; CI, confidence interval; RR, relative risk.
There are currently no data looking at the impact of weight loss on cancer prognosis, but a few large
randomized trials of lifestyle modification that focus on weight loss to prevent disease recurrence and mortality
among early-stage breast cancer survivors are underway. The Breast Cancer Weight Loss Study (BWEL) is a
randomized phase III trial being conducted in the United States and Canada to determine the efficacy of weight
loss on invasive disease-free survival among 3,136 early-stage breast cancer survivors with a baseline BMI ≥27
kg/m2.38 Two trials in Europe also examine how lifestyle modification influences breast cancer recurrence and
survival.39,40 Together, these clinical trials clarify the role for weight management in the prevention of recurrence
and mortality in patients with early-stage breast cancer.41
PHYSICAL ACTIVITY
Physical activity is any form of movement using skeletal muscles that results in energy expenditure.42 Throughout
much of this section, we focus on recreational or leisure-time physical activity, also known as exercise, and

5. associations with cancer risk and outcomes.
PHYSICAL ACTIVITY AND CANCER RISK
In 2007, the World Cancer Research Fund International convened a panel to review the evidence examining the
association between physical activity and cancer risk.43 The panel reviewed more than 250 studies and determined
there was sufficient evidence to conclude that physical activity is associated with a decreased risk of developing
three different types of cancer.43 The evidence supporting the beneficial role of physical activity on the
development of colon cancer was judged as convincing, and the benefits of physical activity on postmenopausal
breast and endometrial cancer were judged as probable. There was also limited, but suggestive, evidence that
physical activity may be associated with a decreased risk of developing lung, pancreatic, and premenopausal
breast cancers.
Despite that hundreds of studies have examined the relationship between physical activity and the risk of colon,
breast, and endometrial cancer, there is less evidence supporting the benefits of physical activity in other cancers.
To address this limitation, a pooled analysis using 12 studies of 1.44 million adults and 26 cancer sites was
conducted.44 This pooled analysis concluded that participation in physical activity was associated with a lower
risk of developing 13 different types of cancer (Table 12.3). It is hypothesized that one of the mechanisms by
which physical activity may lower cancer risk is through the regulation of adiposity.45 However, adjustment for
BMI modestly attenuated associations for several cancers, but 10 of 13 inverse associations remained statistically
significant after adjustment (liver, gastric cardia, and endometrial cancer were no longer significant). This
observation suggests that physical activity may lower cancer risk through mechanisms other than the control of
adiposity (as described later in this chapter).
TABLE 12.3
Summary of Multivariable Hazard Ratiosa for a Higher (90th Percentile) versus Lower (10th
Percentile) Level of Leisure-Time Physical Activity by Cancer Type, without and with
Adjustment for BMIb
Cancer Site or Type
HR (95% CI)
Difference in HR, %Not BMI Adjusted BMI Adjusted
Esophagus: adenocarcinoma 0.58 (0.37–0.89) 0.62 (0.40–0.97) 6.9c
Gallbladder 0.72 (0.51–1.01) 0.78 (0.57–1.06) 8.3c
Liver 0.73 (0.55–0.98) 0.81 (9.61–1.09) 11.0c
Lung 0.74 (0.71–0.77) 0.73 (0.70–0.76) −1.4
Kidney 0.77 (0.70–0.85) 0.84 (0.77–0.91) 9.1c
Small intestine 0.78 (0.60–1.00) 0.81 (0.62–1.05) 3.8
Gastric cardia 0.78 (0.64–0.95) 0.85 (0.69–1.04) 9.0c
Endometrial 0.79 (0.68–0.92) 0.98 (0.89–1.09) 24.1c
Esophagus: squamous cell
carcinoma
0.80 (0.61–1.06) 0.76 (0.58–1.01) −5.0c
Myeloid leukemia 0.80 (0.70–0.92) 0.85 (0.73–0.97) 6.2c
Multiple myeloma 0.83 (0.72–0.95) 0.87 (0.77–0.98) 4.8
Colon 0.84 (0.77–0.91) 0.87 (0.80–0.94) 3.6
Head and neck 0.85 (0.78–0.93) 0.85 (0.77–0.94) 0.0
Rectum 0.87 (0.80–0.95) 0.88 (0.81–0.96) 1.1
Bladder 0.87 (0.82–0.92) 0.88 (0.83–0.94) 1.1
Breast 0.90 (0.87–0.93) 0.93 (0.90–0.96) 3.3
Non-Hodgkin lymphoma 0.91 (0.83–1.00) 0.94 (0.85–1.04) 3.3
Thyroid 0.92 (0.81–1.06) 0.95 (0.81–1.11) 3.3
Gastric noncardia 0.93 (0.73–1.19) 0.92 (0.73–1.15) −1.1

6. Dr. AVR @ TMH
Soft tissue 0.94 (0.67–1.31) 0.97 (0.70–1.34) 3.2
Pancreas 0.95 (0.83–1.08) 0.98 (0.86–1.12) 3.2
Lymphocytic leukemia 0.98 (0.87–1.11) 0.99 (0.88–1.12) 1.0
Ovary 1.01 (0.91–1.13) 1.03 (0.92–1.15) 2.0
Brain 1.06 (0.93–1.20) 1.06 (0.92–1.22) 0.0
Prostate 1.05 (1.03–1.08) 1.04 (1.01–1.07) −1.0
Malignant melanoma 1.27 (1.16–1.40) 1.28 (1.17–1.41) 0.8
BMI, body mass index; HR, hazard ratio; CI, confidence interval.
aAll models were adjusted for age, sex, smoking status (never, former, current), alcohol consumption (0, 0.1–14.9, 15.0–29.9, and
≥30.0 g per day), education (did not complete high school, completed high school, post–high-school training, some college,
completed college), and race/ethnicity (white, black, other). Models for endometrial, breast, and ovarian cancers are additionally
adjusted for postmenopausal hormone therapy use (ever, never), oral contraceptive use (ever, never), age at menarche (<10, 10–
11, 12–13, ≥14 years),Wat menopause (premenopausal, 40–44, 45–49, 50–54, ≥55 years), and parity (0, 1, 2, ≥3 children).
bBMI was calculated as weight in kilograms divided by height in meters squared. Categories used for adjustment were as follows:
<18.5, 18.5–24.9, 25.0–29.9, 30.0–34.9, 35.0–39.9, ≥40.0.
cChange of ≥5% in HR after adjustment for BMI.
Reproduced with permission from Moore SC, Lee IM, Weiderpass E, et al. Leisure-time physical activity and risk of 26 types of
cancer in 1.44 million adults. JAMA Intern Med 2016;176(6):816–825. Copyright (2016) American Medical Association. All Rights
Reserved.
PHYSICAL ACTIVITY AND CANCER OUTCOMES
The bulk of evidence evaluating the relationship between physical activity and cancer outcomes such as
recurrence and mortality is limited to cancers of the breast, colon and rectum, and prostate (Table 12.4). In breast,
colorectal, and prostate cancer, participation in physical activity is associated with a lower risk of cancer-specific
mortality.46 In breast cancer, BMI, menopausal status, and tumor estrogen receptor status do not modify the
relationship between physical activity and cancer-specific mortality. In colorectal cancer, there exists a dose-
response relationship, such that higher volumes of physical activity (minutes per week) are associated with larger
relative risk reductions.47 In prostate cancer, more vigorous intensities of physical activity are associated with
larger relative risk reductions, compared to light- and moderate-intensity physical activity.48,49
SEDENTARY BEHAVIOR
In addition to obesity and physical inactivity, engaging in sedentary behaviors is a risk factor for both cancer risk
and poor prognosis. Sedentary activities are characterized by sitting or lying and often include screen-based
activities, such as television viewing, and smartphone and computer use. In a meta-analysis of 17 prospective
studies, sedentary behavior was associated with a 20% increase in the risk of cancer.50 In another meta-analysis of
14 studies, sedentary behavior was associated with an increased risk of all-cause mortality (22%), cardiovascular
disease mortality (15%), cancer mortality (14%), and incidence of type 2 diabetes (91%).51
TABLE 12.4
Review of Key Meta-analyses Linking Physical Activity to Poor Outcomes in Cancer
Survivors
Cancer Site
Author,
Year,
Reference
No. of
Studies
Sample
Size Exposure Outcome Results Notes
Breast
(postmenopausal)
Friedenreich
et al.,
201646
10 17,666 Highest vs.
lowest
quartile/quintile
of self-reported
physical activity
Breast cancer–
specific
mortality;
cancer
recurrence
HR, 0.62 (95%
CI, 0.48–0.80)
for breast
cancer–
specific
mortality
HR, 0.68 (95%
CI, 0.58–0.80)
for cancer
Dose response:
each 1.5 h/wk
of activity
associated 8%
relative risk
reduction
BMI,
menopausal
status, and

7. recurrence tumor estrogen
receptor did not
modify
relationship.
Colorectal Friedenreich
et al.,
201646
7 9,698 Highest vs.
lowest
quartile/quintile
of self-reported
physical activity
Colorectal
cancer–
specific
mortality
HR, 0.62 (95%
CI, 0.45–0.86)
Dose response:
each 1.5 h/wk
of activity
associated with
6% relative risk
reduction
Prostate Friedenreich
et al.,
201646
4 8,158 Highest vs.
lowest
quartile/quintile
of self-reported
physical activity
Prostate
cancer–
specific
mortality
HR, 0.62 (95%
CI, 0.47–0.82)
Vigorous-
intensity activity
may be more
efficacious than
light- or
moderate-
intensity
activity.
HR, hazard ratio; CI, confidence interval; BMI, body mass index.
INTERVENTIONS
Current public health guidelines encourage participation in 150 minutes per week of moderate-intensity physical
activity for both cancer prevention and survivorship.52 Interventional studies have demonstrated that physical
activity improves quality of life and other patient-reported outcomes during and after cancer therapy. A review of
physical activity intervention studies that included 4,068 cancer survivors demonstrated physical activity reduced
cancer-related fatigue compared to usual care (standardized mean difference [SMD], −0.27; P < .001).53 Another
review that included 3,694 cancer survivors demonstrated physical activity interventions improved overall quality
of life and physical functioning, and reduced anxiety and depressive symptoms.54 Data from randomized clinical
trials also suggest that physical activity improves cardiopulmonary fitness, muscular strength, and body
composition.52,55,56
There are currently no data testing the impact of increased physical activity on risk of cancer recurrence or
mortality among individuals diagnosed with an early-stage malignancy. There are several ongoing randomized
clinical trials that are examining lifestyle-related interventions that include a physical activity component on a
disease endpoint in patients with established cancer. The LIVES trial will examine the impact of physical activity
and diet (emphasizing fat reduction and increased fruit and vegetable consumption) on progression-free survival
among 1,070 patients with advanced ovarian cancer.57 The CHALLENGE trial will examine the impact of
moderate-intensity physical activity on disease-free survival in 962 patients with high-risk stage II or stage III
colon cancer.58 The INTERVAL trial will examine whether vigorous-intensity aerobic and muscle strengthening
exercises can prolong overall survival in 866 men with metastatic prostate cancer.59 Together, these clinical trials
will provide important information regarding the role for physical activity in the prevention of disease recurrence,
progression, and mortality in patients with established cancer.
MECHANISTIC DATA
The specific biologic mechanisms that link obesity and physical activity to cancer risk and prognosis have not
been fully elucidated. It is hypothesized that obesity-related metabolic abnormalities—such as low-grade systemic
inflammation, unfavorable concentrations of insulin, and other metabolic hormones such as leptin and sex steroid
hormones—may promote a host tumor microenvironment that encourages malignant cell growth and
progression.60 The 2016 IARC working group concluded there is strong evidence to implicate inflammation and
sex steroids, and moderate evidence to implicate insulin/insulin-like growth factors as physiologic mediators of
the relationship between obesity and cancer risk and prognosis.16 It has been hypothesized that physical activity
may decrease the risk for various cancer through multiple mechanisms, including sex steroid and metabolic
hormones, inflammation, and immunity.45 A systematic review examined randomized controlled trials with
biomarker endpoints and concluded that physical activity may favorably change circulating concentrations of
insulin, insulin-like growth factors, inflammation, and possibly immunity.61

8. Dr. AVR @ TMH
WEIGHT AND PHYSICAL ACTIVITY GUIDELINES
The American Cancer Society and National Comprehensive Cancer Network have published recommendations on
weight management, physical activity, and nutrition in oncology.52,55 These guidelines recommend that
individuals achieve and maintain a healthy weight throughout life (e.g., avoid excess weight gain at all ages), be
physically active (e.g., engage in 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity activity
each week or a combination thereof), eat a healthy diet with an emphasis on plant foods (e.g., limiting how much
processed meat and red meat consumed, consuming ≥2.5 cups of fruits and vegetables each day, choosing whole
grains instead of refined-grain products), and limit alcohol intake (e.g., no more than one drink per day for women
or no more than two per day for men). Surveys of self-reported lifestyle behaviors suggest that less than one-third
of cancer patients meet these guidelines.62
AMERICAN SOCIETY OF CLINICAL ONCOLOGY OBESITY INITIATIVE
In 2013, the American Society of Clinical Oncology (ASCO) developed an initiative focused on obesity and
cancer. The main objectives of the ASCO initiative were to increase awareness of the evidence linking obesity and
cancer, provide tools and resources to help oncology providers address obesity with their patients, build and foster
a robust research agenda to study the relationship between obesity and cancer and the impact of weight
management programs on cancer outcomes, and advocate for policy and systems change to increase access to
weight management programs for cancer survivors.6 To date, this initiative has facilitated the development of
patient and provider resources to promote healthy weight management (http://www.cancer.net), worked to build
awareness of the relationship between obesity and cancer in the oncology community, and developed a set of
recommendations for future obesity research in cancer populations.63
CONCLUSION
A large body of evidence suggests that both obesity and physical activity are associated with cancer risk and
outcomes. Given the epidemic levels of obesity and physical inactivity around the globe, oncology providers are
likely to encounter a high proportion of patients who are obese and/or physically inactive. Oncology providers are
uniquely positioned to help encourage healthy lifestyle practices that promote weight management and
participation in regular physical activity. The study of energy balance in oncology patients is in its infancy, and
data are rapidly emerging. Many provocative questions remain,64 and numerous clinical trials are underway.
These additional data will allow for more definitive, precise, evidence-based guidance for patients at risk of
developing cancer and those who have an established cancer.
REFERENCES
1. Alfano CM, Bluethmann SM, Tesauro G, et al. NCI funding trends and priorities in physical activity and energy
balance research among cancer survivors. J Natl Cancer Inst 2015;108(1).
2. Shim M, Kelly B, Hornik R. Cancer information scanning and seeking behavior is associated with knowledge,
lifestyle choices, and screening. J Health Commun 2006;11(Suppl 1):157–172.
3. NCD Risk Factor Collaboration. Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled
analysis of 1698 population-based measurement studies with 19·2 million participants. Lancet
2016;387(10026):1377–1396.
4. González-Muniesa P, Mártinez-Gonzalez MA, Hu FB, et al. Obesity. Nat Rev Dis Primers 2017;3:17034.
5. Wang YC, McPherson K, Marsh T, et al. Health and economic burden of the projected obesity trends in the USA
and the UK. Lancet 2011;378(9793):815–825.
6. Ligibel JA, Alfano CM, Courneya KS, et al. American Society of Clinical Oncology position statement on obesity
and cancer. J Clin Oncol 2014;32(31):3568–3574.
7. Wolin KY, Carson K, Colditz GA. Obesity and cancer. Oncologist 2010;15(6):556–565.
8. Cancer Research UK. Public knowledge of the link between obesity and cancer.
https://www.cancerresearchuk.org/sites/default/files/obesity_awareness_executive_summary_final.pdf. Accessed