Reflecting the decades-long increase in obesity rates in the United States, a new study suggests that cancers thought to be at least partly attributable to overweight are also on the rise in those under 50 years of age.
Rates of six of twelve obesity-related cancers have increased in successive generations of young adults, with the largest increases seen in the youngest age groups, researchers reported. The Lancet Public Health.
The new study could serve as a warning: in the coming years, if obesity epidemics persist, there could be an explosion of these fat-sensitive cancers, said the chief author of the study, Dr. Ahmedin Jemal, scientific vice president in charge of surveillance and health. research on services at the American Cancer Society.
"This discovery points to a future increased burden of obesity-related cancers in older adults and calls for action to alleviate this burden," he said in an e-mail.
The researchers analyzed data from a central cancer registry database, focusing on new diagnoses made between 1995 and 2014 on 30 types of cancer, of which 12 are associated with a excess weight. They had complete data from 25 states representing about two-thirds of the US population.
During this 20-year period, there were approximately 14.7 million new cases out of the 30 cancers. For at least eight cancers, including smoking-related and HIV-associated cancers, incidence rates have dropped.
But for six of 12 cancers linked to obesity – colorectal, endometrial, gallbladder, kidney, pancreas and multiple myeloma, the incidence has increased steadily over the years, with larger increases in young adults .
The annual increase in the number of new cases of kidney cancer, for example, was 6.23% among those aged 25 to 29, but about 3% in the 45 to 49 age group. Similarly, the incidence of pancreatic cancer has increased by 4.3% each year among 25-29 year olds, but by less than 1% per year among 45-49 year olds.
Overall, rates of colorectal, endometrial, pancreatic and gallbladder cancers in millennia – young adults born around 1985 – were about double those of people born in the 1950s of the same age, the researchers said. .
The increase in the rate of kidney cancers has been particularly striking. Millennials were nearly five times more likely than baby boomers to develop kidney cancer.
In contrast, for all 18 non-obesity-related cancers except two, rates stabilized or decreased in younger cohorts of successive births.
Jemal hopes the new findings will sound the alarm for doctors treating young adults. "Less than half of primary care physicians routinely evaluate body mass index despite national screening recommendations," he said. "In addition, only one-third of patients report receiving a diagnosis or consultation to lose weight."
Public health measures, such as restrictions on advertising for unhealthy foods loaded with calories, could also be helpful, as well as more campaigns to promote healthy lifestyles, said Jemal.
The issue of cancer and obesity "is a very important topic because we have an obesity crisis for several decades," said John Jakicic, professor and director of the Healthy Lifestyle Institute at the University of Pittsburgh in Pennsylvania . "At one point we started to see that diabetes was following obesity, what we're seeing now is similar to some cancers."
Cancer prevention will most likely involve "prevention of anything that could precipitate cancer," said Jakicic, who did not participate in the study. And although we still do not know exactly how obesity can increase cancer rates, it's "extremely important" to see observational studies showing an association between the two, he noted.