Overweight and obesity have been associated with many health problems, including cancer. A new study has found a link between excess weight and the risk of developing gastrointestinal cancer.
The link between cancer and obesity has been well-researched. The World Cancer Research Fund and the International Agency for Cancer Research have estimated that approximately 20% of cancers may be attributed to excess weight gain.
Previous studies have shown that fat (adipose) cells signal immune cells, which migrate to the areas of the body containing many adipose cells. The resulting inflammation causes cells to divide more quickly, increasing the risk of cancer over time. A new study by Ohio State University Wexner Medical Center researchers examined the association between body mass index (BMI) during different stages of life and the risk of developing GI cancer.
“In a time when obesity rates are rising globally and 70% of the US population alone is considered overweight or obese, understanding the association between obesity and long-term disease risk, such as cancer, is critical for improving public health,” said Holli Loomans-Kropp, lead author of the study.
Before moving on to discuss the study, it’s important to note that some consider BMI, which calculates body fat based on a person’s height and weight, to be an outdated and inaccurate measure because it doesn’t consider muscle mass, bone density, overall body composition and racial and sex differences. The waist-to-hip ratio may be a more accurate metric for measuring health as it relates to weight. Despite its critics, however, BMI remains a standard tool for quickly and easily identifying health risks.
The researchers collected data from 131,161 patients enrolled in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, a clinical trial examining the effectiveness of screening exams to reduce cancer-related deaths, between 1993 and 2001. Participants were randomized into intervention or control groups. Those in the intervention group received screening for prostate, lung, colorectal, and ovarian cancers; the control group received standard care.
BMI was calculated through self-reported questionnaires completed at enrolment using the standard equation: BMI = (weight (lb) / height (in squared)) x 703 or BMI = weight (kg) / height (m squared).
Participants were then categorized according to World Health Organization guidelines: underweight (BMI less than 18.5); normal (18.5 to 24.9); overweight (25 to 29.9); and obese (above 30). In addition, participants reported how often they took aspirin or aspirin-coated drugs in the preceding 12 months. Previous studies found that taking aspirin reduces the risk of GI cancer.
For the purposes of the study, participants were divided into life stages. Early adulthood was considered to be age 20, middle adulthood was age 50, and 55 or older was considered later adulthood.
After following the participants for 13 years, the researchers found that participants who had overweight or obese BMI in early and later adulthood and those who moved from underweight or normal BMI in early adulthood to overweight or obese BMI in later adulthood had an increased risk of all GI cancers, including colorectal cancer.
Taking aspirin did not modify the risk, which, the researchers suggest, might mean that a high BMI offsets the drug's cancer-preventing effects. Additional studies are needed to discern the effect of aspirin on people who are overweight or obese.
The study suggests an association between weight and the risk of developing GI cancer. It does not suggest that overweight or obese BMI is a causative factor.
“We believe that the results of this study highlight the need to better understand the underlying mechanisms of cancer prevention agents as well as who may or may not benefit from their use,” said Loomans-Kropp. "The field of precision prevention is still relatively new but is an exciting avenue for cancer prevention research.”
The study was published in the journal JAMA Network Open.
Source: Ohio State University Wexner Medical Center via EurekAlert!
