More than one-third of U.S. adults are obese, which puts them at higher risk for conditions including heart disease, stroke, and type 2 diabetes, according to the Centers for Disease Control and Prevention. But, gaining some extra pounds could come with even more serious health risks: A new study from the University of Manchester and The Health eResearch Centre has found that significant adult weight gain can increase cancer risk by up to 50 percent.

To reach these findings, researchers examined the body mass index (BMI) of 300,000 men and women from the US. The team looked at changes in BMI between the ages of 18 and 65 and then followed up for an average of 15 years to see who went on to develop obesity-related cancers.

By the age of 65, 9,400 women and 5,500 men participating in the study were diagnosed with an obesity-related cancer.

“This research shows how important it is to look at weight gain over a person’s lifetime — to give a clearer picture of cancer risk through life compared to assessing someone’s BMI at a single point,” lead author Dr Hannah Lennon said in a press release.

“This study could also be really useful in public health. It could help identify people who would benefit the most from taking action to control their weight before any health problems arise — including a cancer diagnosis.”