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Obesity rates rising faster in cancer survivors than in general population

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August 8, 2016

The prevalence of obesity increased more rapidly from 1997 to 2014 among patients with cancer than in the general population, according to the results of a population-based study.

Survivors of colorectal and breast cancers, as well as non-Hispanic black survivors, experienced the greatest increases in obesity rates.
We knew that obesity rates have been increasing in the general population, but we did not know if and how these rates were changing among cancer survivors,” Heather Greenlee, MD, PhD, epidemiologist at Mailman School of Public Health of Columbia University, told HemOnc Today. “We wanted to quantify these changes in order to identify populations that may benefit the most from weight management interventions.”

Heather Greenlee

Heather Greenlee

Greenlee and colleagues analyzed data from 538,969 individuals aged 18 to 85 years who participated in annual cross-sectional National Health Interview Surveys from 1997 to 2014. This population included 33,447 cancer survivors — for whom the most common diagnoses had been breast cancer (n = 6,984), prostate cancer (n = 3,984) and colorectal cancer (n = 2,546) — and 506,522 individuals without a history of cancer.

Researchers defined obesity as a BMI of 30 or more for non-Asian individuals and 27.5 or more for Asian individuals.

From 1997 to 2014, the prevalence of obesity increased significantly among cancer survivors (22.4% to 31.7%), as well as among individuals without a history of cancer (20.9% to 29.5%; P < .001 for trend for both groups).

Researchers noted the prevalence of class I obesity (BMI, 30 to < 35) was consistently higher across all time periods for women survivors (13.6% to 21%) compared with women without a history of cancer (12.2% vs. 16.6%).

The estimated rate of annual increase in obesity prevalence was higher among male and female cancer survivors compared with the noncancer population (all P < .001 for interaction). The annual increase in obesity prevalence among women was 2.9% for those with a history of cancer vs. 2.3% for those without a cancer history, and among men was 2.8% for those with a cancer history vs. 2.4% among those without a cancer history.

Estimated rates of annual increases of obesity prevalence were greater in colorectal cancer survivors (women, 3.1%; men, 3.7%) and breast cancer survivors (3%) compared with adults without a cancer history, but lower in prostate cancer survivors (2.1%; all P < .001 for interaction).

Subgroup analyses based on age, race/ethnicity and cancer type showed obesity prevalence grew more rapidly in every subgroup of colorectal and breast cancer survivors compared with their noncancer counterparts (all P for interaction < .001).

There are likely multiple factors leading to these trends, Greenlee said.

“Although cancer survivors are subject to similar energy balance-related causes of weight gain as the general population, cancer survivors are also at risk for increased weight gain caused by some specific cancer treatments,” she said. “In addition, obesity has been hypothesized to be in the causal pathways for some cancers, including breast and colorectal cancer. Therefore, it is not surprising that obesity rates are higher in these groups.

“Finally, previous studies have shown that breast cancer survivors tend to become more sedentary after diagnosis, which may also lead to weight gain,” she added.

Among colorectal cancer survivors, increasing rates of obesity were greatest for women aged 18 to 44 years (7.95%), men aged 65 to 85 years (3.78%), non-Hispanic black survivors (women, 3.85%; men, 8.44%), women 2 to 9 years from diagnosis (3.32%), and men 10 or more years from diagnosis (5.33%). Among female breast cancer survivors, the highest increasing rates of obesity occurred for women aged 18 to 44 years (5.31%), non-Hispanic white survivors (3.13%), and those 1 year or less from their diagnosis (5.86%; all P for interaction < .001).

These trends could lead to differences in outcomes.

“Observational studies have shown that obesity is associated with decreased survival for some cancer patient populations,” Greenlee said. “However, research by our group and others has shown that the association between obesity and cancer survival varies by cancer type, cancer stage and gender. For some cancers, overweight and obesity may be protective. We need more data to guide us on making definitive recommendations.”

Researchers acknowledged the cross-sectional and self-reported nature of the data as limitations.

“It is well established that obesity can lead to poor health outcomes other than cancer, such as heart disease and diabetes,” Greenlee said. “From a both clinical and public health perspectives, it is important to reverse the growing rate of obesity in cancer survivors. To do so, cancer survivors need access to qualified health professionals who can adequately counsel them on appropriate diet, physical activity and weight management goals. Patients likely need much more that a booklet outlining specific goals; patients likely need proven programs to help them achieve and maintain their goals. A major challenge in this area is that many health insurance plans do cover the cost of these services.” – by Nick Andrews and Alexandra Todak


For more information:

Heather Greenlee, MD, PhD, can be reached at


Disclosure: Greenlee and one other researcher report consultant/advisory roles with EHE International.

itj+ Perspective

Cynthia Thomson, PhD, RDN

Cynthia Thomson

Tracy Crane, PhD, RDN

Tracy Crane

Weight management is important for cancer survivors. Here, researchers identified an overall increase in obesity over a 17-year observational period that was slightly higher (< 1%) in cancer survivors. The higher prevalence of comorbid conditions reported by cancer survivors compared with adults without cancer also is notable.

Speculating on why we might see higher prevalence of obesity in survivors, one might consider that these data reflect a greater focus on cancer treatment and cure and a lower, but necessary, awareness among clinicians of weight gain and weight-associated comorbidity in treating patients with cancer. In fact, studies have shown comorbid, obesity-related conditions such as diabetes influence cancer survival and, thus, should be routinely assessed throughout cancer therapy and beyond.

Although compelling and interesting, the context of these results must be carefully considered. These are observational data and do not capture the impact of weight management within the clinical care setting. Relevant limitations are listed, but some warrant specific attention.

For example, stage of disease at diagnosis matters but was not integrated in these analyses. Individuals with advanced-stage disease are less likely to participate in surveys, suggesting responder bias that could impact the results as presented, especially because nonresponders may actually be prone to weight loss during therapy.

The more relevant question these data cannot answer is the impact of this trend on cancer survival. Among cancer survivorship researchers, there is concern that a singular focus on BMI underestimates the complexities of the bodyweight–cancer survival model in that body composition is largely ignored and yet central to morbidity and mortality risks. Cancer-related treatments commonly reduce lean mass and/or increase intramuscular fat deposition, a physiological change that also is common with aging. Why would this be of concern? Not only may this reduce muscle function, contributing to a trajectory of inactivity and undesirable weight gain, it also may heighten the incidence of comorbid disease, including diabetes, fractures and cardiovascular disease. Further, gain in BMI may be a surrogate for physical inactivity, an exposure that may influence cancer survivorship independent of BMI, as well as cancer-related symptoms such as fatigue.

This manuscript draws attention to the concern for weight gain after cancer diagnosis. Although the researchers identified potentially higher-risk subgroups — including women and non-Hispanic blacks — in reality this analysis reminds us of the importance of monitoring weight in all survivors. If we are to promote the long-term, optimal health of survivors, regular assessment of body composition and obesity-associated comorbid disease risks followed by early intervention utilizing a multidisciplinary approach are needed.

Within the context of cancer treatment, the lack of attention to weight gain could be misinterpreted by patients to mean weight gain is inconsequential in their cancer journey, a message we probably all agree is not optimal.



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Cynthia Thomson, PhD, RDN
University of Arizona Canyon Ranch Center for Prevention & Health Promotion
Mel and Enid Zuckerman College of Public Health
University of Arizona Cancer Center

Tracy Crane, PhD, RDN
University of Arizona Cancer Center

Disclosure: Thomson and Crane report no relevant financial disclosures.