Professor Kathryn Hughes Barry, PhD, MPH, cancer epidemiologist at the University of Maryland School of Medicine discusses how even losing a little weight can lower your chances of getting colon cancer.
Interview conducted by Ivanhoe Broadcast News in July 2022.
So first question I’ll ask you is just a general overview for our viewers. What are you and your colleagues investigating in terms of weight and colorectal cancer?
BARRY: We know that obesity is a risk factor for colorectal cancer, as well as for colorectal polyps, which are benign growths in the colon or rectum that can lead to colorectal cancer. However, there is less known about the role of weight change in adulthood in the risk of developing polyps, and in particular weight loss has been little studied. Most of the studies so far have focused on weight gain. In our study, we looked at both weight gain and weight loss in adulthood in relation to the chance of developing colorectal polyps.
And tell me a little bit about the age range, genders, racial makeup.
BARRY: Our study included both men and women. We drew our study participants from a large cancer screening trial in the United States called the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The participants were between the ages of 55 and 74 when they enrolled in the trial. In our study, we included over 17,000 screening arm participants who had a colorectal cancer screening test at the start of the trial and again several years later as part of the trial. Participants in our study had to have a negative result (no polyps or cancer) on the initial screening test in the trial and no history of colorectal polyps. About 1,000 participants went on to develop a polyp during the several year follow-up period. At the start of the trial, the participants were asked to report their current weight and their past weight at different ages. We used this information to determine their weight change over different periods of adulthood and we looked to see if this weight change was related to the future chance of developing colorectal polyps.
And what did you find?
BARRY: We have a couple of main findings from our study that we’d like to highlight. The first is that losing weight in adulthood, at least two pounds per decade, was associated with a reduced chance of developing colorectal polyps. In particular, we found a benefit of weight loss for adults who were overweight or obese. We also found that weight gain in adulthood was associated with an increased chance of developing these polyps.
Were you able to determine how much of an increase?
BARRY: When we looked at weight loss, we found there was a 46% decreased risk of colorectal polyps for adults who lost weight compared to those with stable weight. On the flip side, gaining weight in adulthood was associated with a 30% increased risk of polyps.
What is it about that change in weight do you hypothesize that may be causing either the development or a lower risk?
BARRY: It is thought that obesity and weight gain may increase the risk of colorectal polyps and colorectal cancer in part by increasing insulin resistance. Insulin is a hormone in the body that helps transport glucose (or sugar) into cells in the body. When insulin is not working well, there can be a buildup of glucose in the blood. The body usually responds by increasing insulin. There may also be some other changes, like increased signaling of insulin-related growth factors. These changes can lead to increased cell growth and reduced cell death, which are features that are linked with an increased chance of cancer. As a result, we believe that weight loss may influence the risk of polyps in part by lowering insulin resistance.
And what are the next steps? What do you plan to study next after building on this research?
BARRY: Our study is one of the first studies to suggest a benefit of losing excess weight in reducing the chance of colorectal polyps. This was an exciting finding to see because it suggests that if someone gains some extra pounds in adulthood, then they may be able to take action to lower their risk by losing some of the extra weight. However, since our study was one of the first to report this finding, it’s really important that this finding is replicated in other studies and particularly in more diverse populations. Our study was conducted in a largely White population based on the participants that were enrolled in the trial that we used for our study. Further study is needed in more diverse populations going forward.
What do the findings suggest to people and to the general population?
BARRY: Based on our findings, we would recommend avoiding weight gain throughout adulthood to help lower the risk of developing colorectal polyps. This, in turn, may help lower an individual’s chance of developing colorectal cancer. Also, adults who are overweight or obese may benefit from losing weight in lowering their risk.
We hear a lot and always for the viewer sitting at home, it always seems like the answer is take off a couple of pounds and it’s preventive. Can you speak to that a little bit, especially in terms of cancer?
BARRY: We know that obesity is related to many different cancers. Colorectal cancer is one of them. There are also other health effects of obesity, such as an increased likelihood of diabetes or cardiovascular disease, for example. It is thought that weight loss may be beneficial with regard to various health conditions. Our study is one of the first to suggest a benefit of losing excess weight in helping to reduce the chance of developing colorectal polyps, which may help reduce the chance of colorectal cancer.
If you could go through some of the other recommendations.
BARRY: There are also other steps that someone can take to help lower their risk of colorectal polyps and colorectal cancer. This includes exercising regularly, eating a diet rich in whole grains, fiber, and fruits and vegetables, and lowering intake of red meat and processed meats like deli meat. We also recommend avoiding smoking and limiting alcohol. We also want to emphasize the importance of regular colorectal cancer screening. This has been shown to save lives from colorectal cancer. There are a few different tests available. The gold standard is the colonoscopy, which can not only detect but also remove polyps and therefore can help prevent colorectal cancer. Notably, the recommendations have changed recently for colorectal cancer screening. It is now recommended for most adults to start screening for colorectal cancer at age 45 instead of age 50. There are also some people in the population who may benefit from starting even younger than 45, for example, if you have a family history of colorectal cancer or you have certain health conditions that put you at higher risk.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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