Approximately two thirds of U.S. adults are considered overweight or obese—a fact many cancer researchers today are watching closely. That’s because obesity increases people’s risk of developing endometrial cancer, liver cancer, pancreatic cancer and colorectal cancer.

A new study in Nature Immunology may help explain the mechanisms behind that deadly link, Medical News Today reports.

According to researchers from Trinity College Dublin and Harvard Medical School and Brigham and Women’s Hospital, extra weight may “clog” the body’s immune cells, increasing the risk of cancer. They discovered this after examining the effects of obesity on what’s immune surveillance, whereby the immune system seeks cancerous or precancerous cells and destroys them before they can cause harm.

More specifically, researchers focused their investigation on natural killer (NK) cells, a type of white blood cell known to combat tumor cells in the body. They used immune cells taken from both humans and mice in a series of experiments and found that in people with obesity, the NK cells became “clogged up” with fat—rendering them unable to destroy tumor cells after binding to them.

Researchers also demonstrated that giving these cells a metabolic jolt restarted their cancer-killing powers. That’s huge, said study authors, because it suggests that experts may one day be able to develop treatments for obese people to mitigate their cancer risk.

“Despite increased public awareness, the prevalence of obesity and related diseases continue. Therefore, there is increased urgency to understand the pathways whereby obesity causes cancer and leads to other diseases and to develop new strategies to prevent their progression,” study authors wrote.

Given that about 40 percent of new cancer diagnoses in the United States are associated with obesity, researchers intend to continue their research far into the future.