Being overweight or obese could be causing as many as one in ten cancer cases, according to new research that suggests the health crisis has been significantly underestimated — with profound implications for public health systems already stretched by chronic disease.
The study, led by Hermann Brenner at the German Cancer Research Center, found that up to 11.5% of cancers may be attributable to being overweight. That's a sharp increase from previous estimates, which placed the figure between 2% and 8%. The research tracked 458,543 women and men from the UK Biobank for an average of 12 years, during which 50,000 new cancer cases were identified. By focusing not just on body mass index but also on waist circumference and waist-to-hip ratio, the researchers uncovered a clearer statistical link between excess weight and cancer risk.
Why Abdominal Fat Matters
The study's methodology marks a departure from earlier work that relied on BMI alone. BMI doesn't distinguish between fat and muscle mass and fails to show how fat is distributed across the body. Michael Leitzmann, an epidemiologist at the University of Regensburg who wasn't involved in the study, said the DKFZ researchers "have not only updated existing risk estimates, but have also questioned whether the link between excess weight and cancer may have been underestimated until now."
Leitzmann explained that fat around the abdomen isn't just a passive store of excess calories. "They trigger what is known as a chronic inflammatory metabolic state," he said. Excess abdominal fat functions like a gland that releases signaling molecules known as adipokines, which travel through the bloodstream and influence cell growth, cell division and the inhibition of programmed cell death. "These are all mechanisms that can contribute to the development and subsequent growth of tumors," he said.
Women Face Higher Cancer Risk
The study suggests that the proportion of overweight women who develop cancer is higher than that of men, though Leitzmann urged caution and said further studies with a similar design are needed to see whether the results can be replicated. Being overweight is blamed for breast, uterine and ovarian cancers, which are hormone-dependent. Estrogen can stimulate the growth of breast cancer, and excess abdominal fat can contribute to elevated estrogen levels.
The researchers also tried to rule out a bias in previous studies by excluding the first few years after enrollment, since cancer can cause weight loss before diagnosis. Only cancer cases that occurred seven years after the start of the observation period were considered, and that made the statistical link between being overweight and cancer clearer.
Prevention Over Treatment
Leitzmann said most people are now aware that obesity increases the risk of cardiovascular disease or Type 2 diabetes, and that losing weight also reduces the risk of heart attacks, strokes and diabetes. He added, "To me, this clearly indicates that, by preventing obesity, we will be able to make a greater contribution to cancer prevention than previously assumed."
Why This Matters:
This research arrives as European health systems face mounting pressure from chronic diseases linked to lifestyle and inequality. If one in ten cancers can be traced to excess weight, prevention becomes not just a medical imperative but a social one. The distribution of obesity isn't random — it tracks income, education, and access to healthy food and safe places to exercise. Addressing the obesity crisis means confronting food industry practices, urban planning that discourages physical activity, and the marketing of ultra-processed foods to children. It also means ensuring that public health campaigns don't stigmatize individuals but instead focus on the structural factors that make healthy living harder for low-income communities. The study's findings strengthen the case for stronger regulation of junk food advertising, investment in public sports facilities, and school nutrition programmes — policies that treat health as a collective responsibility, not an individual failing.