A new study led by Hermann Brenner, an epidemiologist with the German Cancer Research Center, says being overweight or obese could be responsible for more cancer cases than previously known, with abdominal fat in particular increasing the risk of cancer, especially among women. The researchers say obesity could be causing as many as one in ten cancer cases. That’s the hard number. The rest is the familiar public-health machinery trying to catch up after years of pretending the body can be reduced to a neat administrative category.
The Numbers Behind the Warning
The study suggests that up to 11.5% of cancers may be attributable to being overweight. Until recently, researchers believed that 2% to 8% of all cancer cases were attributable to excess body weight. Michael Leitzmann, an epidemiologist at the University of Regensburg who was not 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."
That shift matters because the old method leaned on body mass index, or BMI, alone. BMI doesn’t distinguish between fat and muscle mass and doesn’t show how fat is distributed. The new study moved beyond that blunt instrument and looked at waist circumference and the waist-to-hip ratio too. In other words, it stopped pretending the body fits the spreadsheet so neatly.
The researchers used data from 458,543 women and men from the UK Biobank, one of the world’s biggest health datasets. The participants were followed for an average of 12 years, during which 50,000 new cases of cancer were identified. They also tried to rule out bias in earlier 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.
What the Body Stores, What the Body Pays
Leitzmann said fat around the abdomen is not just a passive store of excess calories. "They trigger what is known as a chronic inflammatory metabolic state," he said. 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.
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. He said being overweight is blamed, among other things, for breast, uterine and ovarian cancers, which are hormone-dependent. He said estrogen can stimulate the growth of breast cancer and excess abdominal fat can contribute to elevated estrogen levels.
Leitzmann also 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."
The study lands as another reminder that the body doesn’t care for bureaucratic simplifications. The risk is real, the data are large, and the warning is plain. What remains is the usual institutional lag: a vast apparatus of research, classification and prevention, arriving late to a problem that has already been living in people’s bodies.