A recently published study in JAMA Oncology examined the risk of colorectal cancer in people who are obese or overweight over a period of years. The study is a population-based, case-control study and was led by Xiangwei Li, MSc, from the German Cancer Research Center in Heidelberg's division of clinical epidemiology and aging research.
In particular, the researchers in this study collected height and self-reported weights from participants in 10-year increments beginning when participants were 20 years old. There were two groups of participants: 5,635 participants with colorectal cancer and 4,515 participants in a control group. The average age of participants in both groups was 68 years, and there were more men than women in both groups.
The researchers found that the longer a person was overweight or obese, the more substantially their odds of developing colorectal cancer went up compared to individuals with a normal body weight. The risk for colorectal cancer in these chronically obese individuals was found to be comparable to the increased risk of cancer in heavy smokers.
Co-author in the study, Dr. Hermann Brenner, MD, MPH, stated, "overweight and obesity are likely to increase the risk of colorectal cancer more strongly than suggested by previous studies that typically had considered body weight only at a single point of time."
Brenner also suggested that this increased risk for the obese and overweight is likely to apply to other cancers as well. "Efforts to prevent their development in childhood, adolescence and young adulthood are particularly important, Brenner emphasized.
A professor at Harvard Medical School and oncologist at Dana-Farber Cancer Institute, Kimmie Ng, MD, MPH, suggested that chronic inflammation and insulin resistance in obese individuals are contributory factors to this increased cancer risk.
A limitation of this study was that participants recalled their weights at different points in their lives through self-reported measures, possibly allowing for errors with accurate recall of weights. Dr. Ng stated more accurate results could be obtained if a study followed people from childhood and documented their weights at specific time points as they're occurring.