Obesity May Cause Up to 11.5% of All Cancers, New Study Finds

Colorectal cancer, breast cancer, liver cancer — the link between excess body weight and at least 13 types of cancer is well established. But a major new study from Germany's Cancer Research Center (DKFZ) suggests the cancer burden of obesity has been substantially underestimated. Up to 11.5 percent of all cancer cases may be attributable to excess body fat — not the 2 to 8 percent previously assumed.

Why the Old Estimates Were Too Low

Previous research relied heavily on Body Mass Index (BMI) as the primary indicator of obesity. But BMI has significant limitations: it does not distinguish between fat mass and muscle mass, and it offers no information about how fat is distributed across the body. The DKFZ team, led by epidemiologist Hermann Brenner, addressed this by incorporating additional measures of body fat distribution.

Epidemiologist Michael Leitzmann of the University of Regensburg, who was not involved in the study, praised the approach: “They have not only updated existing risk estimates but have questioned whether the link between obesity and cancer has been underestimated.”

Abdominal Fat Is Particularly Dangerous

The study finds that fat cells concentrated around the abdomen do far more than store excess calories. Unlike fat stored elsewhere in the body, belly fat triggers chronic systemic inflammation and interferes with hormone signaling — both recognized drivers of cancer development. The risk is especially pronounced in women, though men are not immune.

Conditions specifically linked to excess weight include colorectal cancer, breast cancer, liver cancer, and at least ten additional cancer types. With nearly one in ten cancers potentially related to excess body fat, the findings have significant implications for public health strategies focusing on cancer prevention.

What This Means for Prevention

The researchers emphasize that losing weight, particularly reducing abdominal fat, could prevent a meaningful share of cancers. Strategies include increased physical activity, dietary changes targeting belly fat specifically, and broader public health initiatives around obesity. The study reinforces that obesity is not merely a cosmetic concern but a major modifiable cancer risk factor.