PHYSICIANS SHOULD routinely assess the body mass index (BMI) of their patients and offer counseling and/or referrals to a nutritionist or dietician to patients with a BMI of > 30 kg/m2, Ahmedin Jemal, DVM, PhD, told The ASCO Post. Those actions plus community-level policies designed to increase opportunities for physical activity and reduce consumption of calorie-dense fast foods may counter the rising rates of risk of obesity-related cancers among young adults, he added. Dr. Jemal is Scientific Vice President of the Surveillance and Health Services Research of the American Cancer Society and corresponding author of a study that found the risk of developing 6 of 12 obesity-related cancers increased in successive generations of adults aged 25 to 49 and at a greater pace than among adults older than age 50.

Ahmedin Jemal, DVM, PhD

The study reviewed data on invasive cases of 30 cancer types diagnosed in patients aged 25 to 84 from 1995 to 2014. Compared with people born around 1950, those born around 1985 had a 2 to 5 times increased risk for kidney, gallbladder, pancreatic, and endometrial cancers—nearly twice the risk for colorectal cancer and slightly more than 1.5 times the risk for multiple myeloma.

The study was funded by the Intramural Research Department of the American Cancer Society and the Intramural Research Program of the National Cancer Institute. The results were reported in Lancet Public Health.¹

Steepest Rises in Youngest Groups

THE RESEARCHERS used data from the Cancer in North American database but limited the analysis to 25 U.S. state registries that had data for all the study years (1995–2014). This group represented 67% of the U.S. population. “From 1995 to 2014 there were 14,672,409 incident cases for 30 types of cancer. Incidence significantly increased for 6 of 12 obesity-related cancers (multiple myeloma, colorectal, uterine corpus, gallbladder, kidney, and pancreatic cancers) in young adults (25–49 years), with steeper rises in successively younger generations,” the researcher reported.

In contrast, the incidence increased in successive younger generations for just 2 of the 18 additional cancers not considered obesity-related. “[It] decreased for about half of the remaining cancer types, especially for those related to smoking or HIV infection (eg, lung cancer and Kaposi sarcoma),” the authors noted.

Rapid Rise in Obesity

THE STUDY authors do not definitively claim that obesity is the cause of the increasing incidences, but they noted the increased incidence trends “might have been influenced by the rapid rise in overweight or obesity prevalence in the United States. Between 1980 and 2004, overweight or obesity prevalence in the United States increased by more than 100% among children and adolescents and by 60% among adults aged 20 to 74 years.”

In addition, “The quality of diet has worsened in recent decades among young adults in the United States, with more than half of adults aged 20 to 49 years in 2010 to 2012 reporting poor dietary habits, characterized as low consumption of fruits and vegetables, whole grains, fish and shellfish, and high consumption of sodium and sugar-sweetened beverages,” the authors reported.

“Growing evidence supports an association between childhood or adolescent obesity and increased risk of colorectal, endometrial, and pancreatic cancers and multiple myeloma,” the researchers noted. They cited a study of data from 20 pooled prospective cohorts suggesting that “excess bodyweight during early adulthood (ages 18–21 years) could be a more important influence on pancreatic cancer risk than weight gain later in life. Evidence from multiple murine models,” they added, “suggests that obesity and obesogenic diets can shift the development of cancer to younger age groups.”

“It may be difficult to turn people away from fast food if that is all they can afford. Broad policy changes, such as raising the minimum wage, may be needed.”

— Ahmedin Jemal, DVM, PhD

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Smaller Increases in Older Adults

WITH TWO EXCEPTIONS, the incidences of the obesity-related cancers that increased in younger adults also increased in older adults, although the magnitudes of annual percent increases were smaller in older than in young adults. Those exceptions are colorectal cancer, “which declined, and uterine corpus cancer, which increased in [people between the] ages of 50 and 69 years but decreased in older women,” the researchers reported.

In an American Cancer Society research article about the study, one of the takeaway messages highlighted follows: “Older adults still get more cancers than younger adults….”²

As noted in the study report, the increase in early-onset colorectal cancer has been reported previously and “may partly reflect the obesity epidemic.” Dr. Jemal was coauthor of two studies published in 2017; they found that younger adults were increasingly being diagnosed with and dying of colon and rectal cancers.^3,4 The current study builds on those previous studies.

Community-Level Interventions

“DUE TO THE OBESITY EPIDEMIC over the past 40 years, younger generations worldwide are experiencing an earlier and longer lasting exposure to excess adiposity over their lifetime than previous generations,” the researchers wrote. In addition to the important role of health providers in assessing and addressing the weight of their patients, “innovative strategies are needed to mitigate morbidity and premature mortality associated with obesity-related disease,” the authors stated. These strategies may include community-level regulatory interventions such as urban planning for promoting physical activity, taxes on sugar-sweetened beverages, and restriction of advertising for calorie-dense food and soft drinks. These interventions, however, “have yet to be implemented broadly, despite growing empirical evidence for their effectiveness,” the authors stated.

Dr. Jemal likened the effort to increasing cigarette taxes and implementing smoking restrictions in public places. Those policies started in just a few cities and then grew nationwide. Policy changes and regulatory interventions to reduce obesity will also be introduced incrementally, he said. “It takes time for broad implementation of such interventions.”

“It is difficult to change habits,” he said, but “changing dietary behavior won’t be as hard as smoking, because smoking is addictive.” He acknowledged that fast food can also seem like an addiction. In addition, it may be difficult to turn people away from fast food if that is all they can afford. Broader policy changes, such as raising the minimum wage, may be needed. Dr. Jemal cited an article in The New York Times that described the plight of minimum-wage earners who have to rely on fast foods because they cannot afford to buy fruits and vegetables and other healthy foods.⁵ ■

DISCLOSURE: Dr. Jemal reported no conflicts of interest.

REFERENCES

1. Sung H, Siegel RL, Rosenberg PS, et al: Emerging cancer trends among young adults in the USA: Analysis of a population-based cancer registry. Lancet Public Health 4:e137-e147, 2019.

2. McDowell S: Study: Millennials’ increased risk for some obesity-linked cancers—5 takeaways. American Cancer Society. February 26, 2019. Available at https://www.cancer.org/latest-news/study-millennials-increased-risk-for-some-obesity-linked-cancers.html. Accessed March 26, 2019.

3. Siegel RL, Fedewa SA, Anderson WF, et al: Colorectal cancer incidence patterns in the United States, 1974–2013. J Natl Cancer Inst 109(8), 2017.

4. Siegel RL, Miller KD, Jemal A: Colorectal cancer mortality rates in adults aged 20 to 54 years in the United States, 1970–2014. JAMA 318:572-574, 2017.

5. Desmond M: Dollars on the margins. The New York Times, February 21, 2019. Available at https://www.nytimes.com/interactive/2019/02/21/ magazine/minimum-wage-saving-lives.html. Accessed March 26, 2019.