Obesity, already associated with a litany of other diseases, is now the number one cause of cancer among non-smokers. However, strategies aimed at avoiding obesity are often undermined by people’s lifelong eating habits. To help people break these habits and avoid obesity—and the cancer risk that accompanies it—researchers at The University of Texas MD Anderson Cancer Center are investigating a new weight management approach that helps people rethink their relationship with food.
The weight management approach uses glucose monitoring to help people manage their food intake. A clinical trial is under way to see if this approach can improve weight losses achieved during a 16-week lifestyle intervention for obese postmenopausal women at high risk of developing breast cancer.
A major risk factor
Obesity is known to increase the risk of colorectal, endometrial, and post-menopausal breast cancers; cancers of the pancreas, kidneys, liver, thyroid, stomach, gallbladder, esophagus, and ovaries; and meningioma and multiple myeloma. Whether losing weight decreases this risk is less clear, however.
“Epidemiological data show that being obese is associated with increased cancer risk, but we don’t yet have a lot of data about how weight loss affects cancer risk,” said Karen Basen-Engquist, Ph.D., a professor in the Department of Behavioral Science. “We do have some data showing that weight loss is associated with a decreased risk of developing endometrial cancer, and we’re starting to see data showing that a large amount of weight loss after bariatric surgery is associated with decreased cancer risk.”
Although the exact mechanisms are unclear, obesity is believed to increase the risk of cancer primarily through the accumulation of adipose tissue. Adipose tissue—fat—is very active metabolically and secretes numerous growth factors and hormones associated with cancer development and progression. For example, adipose tissue secretes estrogen, which drives many breast cancers, as well as vascular endothelial growth factor, which enables malignant transformation by promoting angiogenesis. Because obesity often goes hand in hand with a poor diet, diet-related factors may also contribute to the development of cancer. Genetics, too, may play a role in the relationship between obesity and cancer.
“It’s probably not just one thing we can point to, but a number of characteristics that are linked with obesity that help drive increased cancer risk,” Dr. Basen-Engquist said, “and the driving characteristics might be different for different types of cancer.”
Importance of achieving balance
Energy balance—the state in which the number of calories a person expends is equal to the number of calories that person consumes—is key to staying at a healthy weight, said Susan Schembre, Ph.D., an assistant professor and registered dietitian in the Department of Behavioral Science.
“Food is fuel and nutrients; it’s not anything other than that physiologically,” Dr. Schembre said. “But we eat for other reasons. We eat to celebrate, or reward ourselves, or comfort ourselves.”
In other words, a desire to eat may not be connected to a physiological cue for the need for fuel. This disconnect is encouraged by intensive weight-loss interventions that focus on strictly scheduling eating times to offset the tendency to eat outside those periods. And once these interventions end, patients drift back to the poor eating habits they had beforehand.
“People’s relationship with food and their disconnect from physiological cues can interfere with their ability to control their weight,” Dr. Schembre said. “We need to provide people with the skills to understand their relationship with food and learn how to self-regulate.”
To help people sever their unhealthy connections with food and better manage their weight, Dr. Schembre and other researchers are turning to an intervention called “Hunger Training.” The aim of Hunger Training is to teach people to recognize when they are truly hungry—i.e., when they have a negative energy balance and their bodies need fuel.
Patients who practice Hunger Training use glucose monitors to assess their need for food. (Glucose is used as a biomarker of short-term energy status; it serves as a proxy for a physiological need for food.) The glucose monitor—typically a small patch-like apparatus placed on the upper arm and secured with adhesive—connects wirelessly to a reader that allows patients to check their glucose levels in real time. A blood glucose level at or near a person’s fasting level is the threshold that signals “true hunger,” or an energy deficit and a need to eat.
“With Hunger Training, there are no other dietary recommendations; it’s just, don’t eat if your glucose is above your threshold,” Dr. Schembre said.
Hunger Training typically lasts 3–4 weeks. Once patients learn to associate feelings of true hunger with the number on the glucometer—i.e., they’ve learned to sense what true hunger is and eat accordingly—they stop Hunger Training.
Recent trials of Hunger Training have been promising, Dr. Schembre said. “People using this intervention have lost up to 7% of their initial body weight within 5 months. These results are as good as if not better than other more intensive interventions, which typically achieve an average of 5% weight loss,” Dr. Schembre said.
Whether such results are enduring has not yet been tested, and Dr. Schembre said that she expects a “booster” program might be necessary to reorient participants to the training in the long term.
Dr. Schembre and her colleagues have opened a clinical trial (No. 2017-0507) to determine the effects of Hunger Training on weight loss in obese postmenopausal women with a high risk of developing breast cancer. The trial is enrolling women who have a body mass index of 30 kg/m2 or higher and are identified as being at high risk for cancer based on their background and medical history. Future studies of Hunger Training may look at the relationship between obesity and cancer in different populations.
“We’ll have opportunities to investigate this intervention in other populations, such as cancer patients receiving treatment and cancer survivors, but we’re taking it one step at a time,” Dr. Schembre said.
For more information, contact Dr. Karen Basen-Engquist at 713-745-3123 or firstname.lastname@example.org or Dr. Susan Schembre at 713-563-5858 or email@example.com. For information about the Hunger Training trial for postmenopausal women at high risk of breast cancer, visit www.clinicaltrials.org, call 713-794-5494, or email firstname.lastname@example.org.
OncoLog, April 2018, Volume 63, Issue 4
Outreach Programs Help Communities Overcome Obstacles to Healthy Living
Preventing obesity requires more than individual motivation. People’s environments also shape their opportunities for a healthy lifestyle, said Lorna McNeill, Ph.D., M.P.H., an associate professor in and chair of the Department of Health Disparities Research.
“We have to realize that people are affected by their family and culture and upbringing,” Dr. McNeill said. “We can’t just focus on the individual and think that we’re going to make lasting changes. We have to consider the context in which that person lives.”
Dr. McNeill develops interventions that work within the context of people’s social environment to help them overcome obstacles to a healthy lifestyle. Her projects are largely directed at minority populations in underserved communities, whose risk for obesity is higher than that of the general population. These projects, which focus on social support, particularly among women, have included recruiting participants for a yoga-based intervention through churches and setting up a healthy food co-op in a church in a food desert (an area with limited access to nutritious food).
One of Dr. McNeill’s main goals is to understand the relationship between environment and physical activity—specifically, how environment affects people as they adopt physical activity and how it affects them after they have adopted and maintained the behavior.
Overcoming environmental barriers to activity requires placing innovative, evidence-based programs in the community so that more people have access to them, Dr. McNeill said. She added that the main challenge in these programs is finding ways to sufficiently engage people to ensure their long-term adherence to the behaviors the interventions foster.
“Some interventions can get people to change their behavior to lose weight over 3 months, but then they regress, and we don’t yet know how to get people to maintain what they’ve started,” Dr. McNeill said. “As researchers, that’s the hardest obstacle we still haven’t been able to crack.”
To learn more about MD Anderson’s Department of Health Disparities Research, visit http://bit.ly/2DLytOA.