Cancer is an ever-present health concern, especially as you age. But a recent study has found that some types are increasing dramatically in young people.

A study published in the Lancet Public Health from the American Cancer Society analyzed 20 years of data on cancer diagnoses in adults ages 25 to 84 and found surprising increases in cancer rates in people between 25 and 49, specifically in types related to obesity.

Of the 12 obesity-related cancer types studied, six types showed the largest spike in numbers for young Americans. Those cancers are colorectal, endometrial, gallbladder, kidney, pancreatic, and multiple myeloma, a cancer of plasma cells—cancers that typically show up in patients in their 60s or 70s.

Americans aged 25 to 29 had the greatest increases in kidney cancer, with an average annual increase of 6.23%, while people aged 30 to 34 had the largest increase in multiple myeloma, at 2.21%.

Incidence in young adults also increased for two cancers that aren’t linked to obesity: gastrointestinal cancer and leukemia.

What’s causing the increases?

While the study did not focus on the specific causes of the increases in these cancer rates, it did hypothesize that the trends may be influenced by the rise in overweight and obese Americans.

According to the CDC, between 1999 and 2016, obesity prevalence in the U.S. increased from 13.9% to 18.5% among children and adolescents and from 30.5% to 39.6% among adults. This is important because research has shown that being overweight or obese can increase your risk for certain cancers.

A separate 2018 study found that excess body weight may have accounted for up to 60% of all endometrial cancers, 36% of gallbladder cancers, 33% of kidney cancers, 17% of pancreatic cancers, and 11% of multiple myelomas that occurred in 2014.