Being overweight may contribute to far more cancer cases than previously thought, according to new research from the German Cancer Research Center (DKFZ). By using more accurate measures of body fat and accounting for methodological biases that may have distorted earlier findings, researchers estimate that more than 10% of all cancer cases could be attributed to excess body weight—almost double previous estimates. The findings suggest that obesity plays a much larger role in cancer development than has long been recognised.
To investigate the relationship between excess weight and cancer, the researchers analysed data from 458,543 adults enrolled in the UK Biobank. Participants were followed for a median of nearly 12 years, during which more than 50,000 new cancer cases were recorded. While overweight and obesity have long been established as risk factors for several cancers, earlier studies estimated they accounted for only around 2–8% of cases. Epidemiologist Hermann Brenner and his colleagues suspected these figures were underestimated because of limitations in the way body fat and cancer risk had been assessed.
Most previous studies relied on body mass index (BMI), which is calculated using height and weight. However, BMI cannot distinguish fat from muscle or indicate where fat is stored. Fat accumulated around the abdomen is particularly metabolically active and is strongly linked to chronic inflammation and other biological processes that can promote cancer. To address this limitation, the DKFZ team also examined waist circumference and waist-to-hip ratio, finding that these measures of body fat distribution were considerably better predictors of cancer risk than BMI alone.
The researchers also addressed an important source of bias that may have weakened previous estimates. Many cancers cause unintentional weight loss years before diagnosis, meaning some participants who already had undetected tumours appeared leaner when they entered the study. This can reduce the apparent association between obesity and cancer. To minimise this effect, the team progressively excluded cancers diagnosed during the first years of follow-up, as these cases were more likely to have been present before the study began. Once this bias was accounted for, the relationship between excess weight and cancer became much stronger.
After incorporating these methodological improvements, the estimated proportion of cancers attributable to excess weight increased from approximately 5.5% to as high as 11.5%. In other words, more than one in ten cancer cases may be linked to excess body fat and could potentially be prevented through effective weight management. The analyses also indicated that the impact of obesity may be greater among women than men and may be particularly important in adults younger than 60 years.
According to Brenner, the findings highlight the growing public health challenge posed by rising obesity rates worldwide. As populations continue to age and obesity becomes increasingly common, the number of obesity-related cancer cases is expected to increase substantially. The researchers argue that more effective strategies to prevent and treat obesity could have a far greater impact on reducing the burden of cancer than previously believed, reinforcing the importance of maintaining a healthy body weight as part of long-term cancer prevention.
More information: Luna Kiran Adhikari et al, Excess Weight May Account for More Than 10% of All Cancers: The Underestimated Impact of the Obesity Epidemic, Cancer Communications. DOI: 10.34133/cancomm.0040
Journal information: Cancer Communications Provided by German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ)
