"Given the large increase in the prevalence of overweight and obesity among young people and increasing risks of obesity-related cancers in contemporary birth cohorts, the future burden of these cancers could worsen as younger cohorts age, potentially halting or reversing the progress achieved in reducing cancer mortality over the past several decades".
Chris Macdonald, Head of Research at Pancreatic Cancer UK said: "The study reveals some striking findings and offers a compelling theory that the recent increase in obesity in the population drives the disproportionate increase in risk of pancreatic cancer in young adults".
Still unexplained, however, is why the six other forms of cancer classified by the UN's International Agency for Research on Cancer (IARC) as related to obesity did not also show similar rates of increase among younger adults.
The report stated that the obesity-related cancers which were increasing among the youth were colorectal, endometrial, gallbladder, kidney, pancreatic and multiple myeloma (bone marrow cancer). It can increase inflammation, which is a risk factor for a number of chronic conditions and has been found to fuel cancer cell growth.
Cancers related to obesity are on a steep rise among millennials, a new study by the American Society has found. Researchers warned that in six out of 12 obesity-related cancers (colorectal, uterine, gallbladder, kidney, pancreatic, and multiple myeloma), the number of cases went up in people under the age of 50.
"Importantly, the findings suggest the need for further close epidemiological monitoring of cancer incidence trends in younger adults", Birmann told BBC. Especially striking was the rising rate of kidney cancers. And while we don't yet know exactly how obesity may be driving up cancer rates, it's "critically important" to see observational studies that that show an association between the two, he noted.
The researchers then estimated the change in incidence rates for each of the cancers within five-year age groups, beginning with 25-29 and ending with 80-84.
For example, in pancreatic cancer the average annual change was equal to or less than one per cent in people aged 40 to 84, 1.3 per cent in those aged 35 to 39, and 2.5 per cent in 30 to 34-year-olds.
Although screening for most of these cancers isn't available or useful for younger patients, colon cancer is an exception, Jemal said.
Over the past few decades, scientists have uncovered an increasing body of evidence linking obesity to the development of certain cancer types. If trends continue as projected carrying excess weight could cause even more cases of cancer in women than smoking within 25 years.
"A patient who is obese will be at higher risk for complications and often times more severe complications from surgery than someone at an optimal weight", Chang said.
As for gastrointestinal cancer and leukemia, the researchers hypothesize that increases in autoimmune disease, antibiotic use, and exposure to environmental carcinogens may be to blame.
More effort is needed to combat the obesity epidemic, experts say.