Obesity significantly increases the risk of cancer in various organs. Although this has been recognized for decades, the mechanism by which this occurs has never been explained. CT scans of 750 people show that overweight people (obese) have larger organs and therefore more cells. This could explain why obese peoplea higher riskfor many types of cancer.
The number of people with obesity is increasing worldwide. According to the WHO definition, obesity occurs in people with a body mass index (BMI) of 30 kg/m² (body weight: height in m). Obesity is now considered a risk factor for many diseases and is also the focus of research as probably the most studied risk factor for cancer. Despite efforts to date, the mechanisms underlying the effects of obesity on cancer risk have proven elusive.
“Although obesity is a complex disease that can influence cancer risk in several other ways, the size of an organ and the number of cells can significantly increase the risk of cancer in that organ,” explains the team, led by Cristian Tomasetti at the Faculty of Medicine of the Johns Hopkins University.
The researchers have threedifferent organs analyzedto find out whether obesity has an impact on the size of our organs and therefore the total number of cells. They found a significant linear relationship between the increase in organ volume and the increase in cancer risk.
The study found that overweight people (BMI ≥ 30) had an average of 55%, 68% and 39% larger kidneys, liver and pancreas, respectively. These results explain why obese people have a higher risk of cancer in several organs: the larger the organ volume, the more cells are at risk of cancer. These results are important for a better understanding of the effects of obesity on cancer risk and, more generally, for the development of better prevention strategies to limit obesity-related mortality.
Other epidemiological studies also support this hypothesis by showing that taller people have a higher risk of cancer, with an estimated average increase in overall cancer risk of 16-18% for every 10 cm of additional height and comparable estimates for each organ. There are also strong connections between body size and organ sizes, for example an increase in colon length of 1.5 cm - and the associated increase in the number of cells - for every centimeter of additional height.
The study was conducted on July 29, 2020published in bioRxiv.
