Examining Obesity and Cancer

AACR Special Conference highlighted the connections between weight and cancer.

The message never changes: Maintaining a healthy body weight can lower our risk of numerous health problems, including 14 types of cancer.   

Still, many people discover that it’s not easy to stay slim. Recent statistics from the National Institutes of Health indicate that over 70 percent of American adults are overweight or obese. Rates of childhood obesity continue to rise in the Unites States: About 1 in 6 children ages 2-19 are considered obese.   

The connection between obesity and cancer was examined in detail at a recent American Association for Cancer Research (AACR)  Special Conference, Obesity and Cancer: Mechanisms Underlying Etiology and Outcomes, in Austin, Texas.   

Along with explorations of how obesity triggers inflammation, insulin resistance, and other cellular pathways, paving the way for the growth of malignant cells, the conference featured numerous presentations that examined how obesity affects certain types of cancer, and how society can potentially stem the tide of obesity. Here’s a sampling of research highlighted at this important AACR meeting:   

Obesity in Canada

The United States is not alone in the struggle with obesity.

A study presented at the conference indicated that in 2011, the prevalence of overweight and obesity in Canada was 32.7 percent and 17.8 percent, respectively. If current trends continue, by 2032, the prevalence of overweight and obesity will be 31.2 percent and 27.9 percent, respectively, said the study’s lead author, Darren Brenner, PhD, assistant professor in the departments of Oncology and Community Health Sciences at Cumming School of Medicine, University of Calgary, Alberta, Canada.

Dr. Brenner and colleagues studied scenarios of possible interventions that would reduce the prevalence of excess body weight, and found that reducing the number of overweight and obese Canadians by 50 percent could potentially prevent a cumulative 59,829 cases of cancer by 2042.

Body fat, not just weight, contributes to breast cancer risk

There’s more to the obesity-cancer connection than meets the eye.

One study presented at the conference showed that among postmenopausal women with normal body mass index (BMI), those with higher body fat levels were at higher risk of developing invasive breast cancer.   

The study, led by Neil Iyengar, MD, medical oncologist at Memorial Sloan Kettering Cancer Center, showed that women in the highest quartile of whole body fat mass had approximately a doubling in the risk for ER-positive breast cancer compared with women in the lowest quartile.   

Dr. Iyengar and colleagues also found that the risk of ER-positive breast cancer increased by 35 percent for each 5-kilogram increase in whole body fat, despite having a normal BMI.

The study’s authors explained that while BMI is a convenient way to estimate body fat, it does not provide an exact picture, as muscle mass and bone density cannot be distinguished from fat mass. Therefore, women may want to seek out information on their body fat composition, even if they are at a healthy weight. Meanwhile, physical activity likely carries benefits for all people.    

Obesity and prostate cancer recurrence

Evidence increasingly shows that obesity can affect cancer outcomes, often leading to increased chances of cancer recurrence or progression.   

One study presented at the obesity conference showed that among men with prostate cancer who underwent radical prostatectomy (RP), those who were obese had a higher risk of biochemical recurrence.

Arash Samiei, MD, basic scientist and clinical researcher at the Department of Urology at the Allegheny Health Network in Pittsburgh, and colleagues conducted a retrospective study of all RPs (1,100 surgeries) performed by two surgeons at Allegheny General Hospital in Pittsburgh between 2003 and 2013. They determined that biochemical recurrence was more common in the patients who were obese, as well as in the patients with metabolic syndrome—a collection of risk factors such as a large waistline, high triglycerides, and high blood sugar, which often lead to severe health problems.

"These individuals should have more focused follow-up care," Samiei said. "By preventing metabolic syndrome, men with prostate cancer may have a higher chance of a favorable oncological outcome following surgery."

How a good night’s sleep may help children stay fit

Childhood obesity very often leads to adult obesity, so teaching children healthy habits may produce long-term benefits, said Bernard Fuemmeler, PhD, MPH, professor and associate director for cancer prevention and control at Virginia Commonwealth University’s Massey Cancer Center.

Among those healthy habits? A good night’s sleep.   

Fuemmeler and colleagues conducted a study in which 120 children wore accelerometers to track their sleep-wake cycle for at least five days. Overall, shorter sleep duration was associated with higher body mass index. Several measures of the quality of sleep (fragmented sleep, earlier waking, and more) were associated with higher BMI and more frequent snacking.   

Fuemmeler said that parents should adhere to guidelines on sleep set by the American Academy of Pediatrics, which include regular bedtime routines and no screens in the bedroom.

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