The World Cancer Research Foundation considers (pdf) obesity as a possible cause of colorectal cancer (colon cancer). The organization makes this conclusion in connection with the large number of studies that demonstrate the connection between cancer and excess weight. Some evidence suggests that losing weight reduces these risks. At the same time, it was not known for sure whether the risk of colorectal cancer increases with obesity in men and women equally.
Obesity is talked about when a person’s body mass index (BMI) is above 30. To calculate BMI, a person’s weight in kilograms must be divided by the square of their height in meters. A normal BMI is 18.50 – 24.99.
In the new study, scientists from the University of Bristol and the International Agency for Research on Cancer included more than 100 thousand people, the data on which are contained in the British Biobank. Scientists did not weigh each participant in the study, but used genetic data. Certain markers in genes indicate the risk of obesity of different types and severity. Thus, the authors of the study analyzed how the genetic predisposition to obesity is associated with the risk of cancer. This technique is called Mendeleev randomization.
It turned out that an increase in BMI – a standard indicator for assessing obesity – is more strongly associated with the risk of colorectal cancer in men. With its increase for every 4.2 units, the likelihood of developing this tumor in men increased by 23%, in women – by 9%.
At the same time, a different indicator indicated the connection between cancer and changes in body shape and body fat in women. An increase in their waist-to-hip ratio for every 0.07 units in them was associated with an increase in the risk of colorectal cancer by 25%. For men, this figure was only 5%.
The waist-to-hip ratio is an indicator that increasingly attracts the attention of doctors. WHO experts are confident that it can indicate the risk of a number of chronic diseases.
The authors write that such studies are needed to better understand why obesity is associated with cancer risk. It’s not always easy for people to lose weight. Understanding the harmful effects of obesity would help improve their health.