Weight loss for adults, particularly those who are overweight or obese, may reduce their risk of developing a type of polyp that can lead to colorectal cancer, according to a new study led by researchers at the University of Maryland School of Medicine (UMSOM). Findings were published in the journal JNCI Cancer Spectrum.
Losing weight from early to late adulthood (up to the mid-70s) – at least two pounds per decade – reduced an individual's risk for developing precancerous growths, or adenomas, by 46 percent, the investigators reported. Study findings particularly support a benefit of weight loss for adults who are overweight or obese. Weight loss among those who were overweight or obese at age 20 was associated with a more than 60 percent reduction in risk, whereas there was no association for those with a lower body mass index at age 20.
On the flip side, gaining weight through the decades increased a person's risk of developing colorectal adenomas. The study found that gaining about six pounds or more every five years was associated with a 30 percent increased risk of this type of growth.
"Our research suggests that avoiding weight gain in adulthood may help lower an individual's chance of developing colorectal adenomas, which may in turn reduce the risk of developing colorectal cancer," said the senior author, Kathryn Hughes Barry, PhD, MPH, Assistant Professor in the Department of Epidemiology and Public Health at the UMSOM and a cancer epidemiology researcher at the University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center. "Our results also suggest that weight loss in adulthood, especially for adults who are overweight or obese, may help reduce the risk of colorectal adenoma, among other potential health benefits."
Shisi He, MS, a doctoral student in molecular epidemiology in the Department of Epidemiology and Public Health at UMSOM, is the first author of the study.
More than 73 percent of adults in the United States aged 20 years and older are overweight or obese, according to the U.S. Centers for Disease Control and Prevention. Obesity is a risk factor for colorectal adenomas and colorectal cancer, which is the third most common cancer and the third leading cause of cancer-related death among both men and women in the U.S. Overall, the death rate from colorectal cancer has decreased in part as the result of better screening and earlier detection but has been on the rise in younger adults.
Dr. Barry said that previous research has primarily focused on adenoma risk relating to obesity or body mass index at one point in time rather than through the years. Fewer studies have evaluated the role of weight changes in adenoma risk. Of these studies, most focused on weight gain.
In the current study, researchers examined weight change – both weight gain and weight loss – over three periods of adulthood in relation to colorectal adenoma. The researchers used data from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening trial, which was a large randomized controlled trial in the United States that enrolled 154,942 men and women ages 55 to 74 from 1993 to 2001 to evaluate the effectiveness of different screening approaches in preventing death from colorectal cancer, among other cancers.
The current study evaluated 17,629 PLCO screening arm participants who had available weight data, reported no history of colorectal polyps or other colon conditions, received a negative result (no polyps or cancer) on a screening test called flexible sigmoidoscopy at the start of the trial, and received a follow-up sigmoidoscopy three or five years later. Of these, slightly more than 1,000 people went on to develop an adenoma in the lower part of the colon (distal colon) or rectum in the follow-up period. The participants self-reported their past weight at different ages at the start of the trial.
"Our study is unique because we were able to study both weight loss and weight gain in different time periods in adulthood in relation to colorectal adenoma. A further strength was our ability to study newly-developed adenomas by leveraging data from colorectal cancer screening tests at two different time points in the PLCO trial," Dr. Barry said. "This helped reduce the possibility that existing disease could have caused the weight change, rather than the other way around."
"Obesity is a known risk factor for colorectal cancer, which remains a leading cause of cancer related-death in the United States," said E. Albert Reece, MD, PhD, MBA, Executive Vice President for Medical Affairs, University of Maryland, Baltimore, and the John Z. and Akiko K. Bowers Distinguished Professor and Dean of UMSOM. "The results of this study underscore the importance of maintaining a healthy weight throughout adulthood to help prevent adenomas – which could ultimately result in a decrease in colorectal cancers. This public health message could help to save lives."