A new analysis raises the alarm that the rates of obesity-related cancers are rising in younger and younger adults. Findings from a new study published in The Lancet Public Health indicate that six obesity-related cancers have significantly increased between 1995-2014 and the risk of these cancers is increasing in each successive younger age group. These cancers include colorectal, pancreatic, gallbladder, kidney cancer and multiple myeloma (a type of blood cancer). These cancer types are particularly concerning because they are very serious and account for over 150,000 deaths in the U.S. every year.
The findings were built on the researchers’ previous work demonstrating that the incidence of colorectal cancer in the U.S. has increased in recent decades, especially among younger adults. Colorectal cancer is an obesity-related cancer. “We wanted to find out whether there was a similar increase in incidence of other cancers related to obesity,” says Ahmedin Jemal, DVM, PhD, the vice president of the Surveillance and Health Services Research Program at the American Cancer Society, and the senior author of the study.
The current study was based on cancer incidence data for people aged 25 to 84 years between January 1995 and December 2014. Data was obtained from the Cancer in North America database of the North American Association of Central Cancer Registries. The researchers limited their analysis to data pooled from 25 state cancer registries, covering more than two-thirds of the population living in the U.S.
Statistical analysis revealed that during the 20-year period under study, incidence of six of the 12 known obesity-related cancers – colorectal, endometrial (also known as uterine corpus), gallbladder, kidney, multiple myeloma, and pancreatic – increased in the U.S., and the risk of developing these cancers increased within each successively younger age group.
Although the rates of obesity-related cancers also rose among older adults, the magnitude of change was greater among younger adults. The greatest annual percent change increases by age were observed among young adults between the ages of 25 and 29 years for kidney (6.23 percent), gallbladder (3.71 percent), endometrial (3.34 percent), and colorectal cancers (2.4 percent). The annual percent change for people between the ages of 30 and 34 years for multiple myeloma increased by 2.21 percent.
The analysis showed an escalating risk among younger generations for obesity-related cancers. For example, “The risk of developing endometrial cancer among millennials is twice as high as the risk among baby boomers of the same age,” says Jemal.
The authors of the study suggest that this shift in the trend toward increased younger adult cancer incidence may be due to the rapid rise in overweight or obesity prevalence. According to the Centers for Disease Control and Prevention, obesity rates among children and teens have more than tripled since the 1970s. A growing body of evidence from experimental studies suggests that having obesity or overweight can speed up the multistep processes involved in the development of cancer, potentially explaining the changes in cancer trends. In addition, people having overweight or obesity may engage in behaviors that increase cancer risk, such as a sedentary lifestyle, extensive screen time, or eating a diet high in processed or red meat and low in fruits and vegetables.
The findings from this study highlight the need for interventions that address the obesity epidemic. “If there is no intervention, the burden of obesity-related cancers in older adults is likely to be much higher in the future,” says Jemal. “This is a bellwether. We haven’t seen the full impact of the obesity epidemic on cancer burden.”
Sung, Hyuna, et al. “Emerging cancer trends among young adults in the USA: analysis of a population-based cancer registry.” The Lancet Public Health (2019).