Obesity is a global epidemic. This public health crisis and the growing body of evidence linking obesity with cancer risk[2,3,4] have prompted the American Society of Clinical Oncology (ASCO) to launch an initiative addressing the issue of obesity, particularly as it affects cancer patients and survivors. A special session held during the ASCO annual meeting, entitled "ASCO Obesity Initiative: Weight of the Evidence," explored the best evidence on the link between obesity and cancer, and key strategies for helping cancer patients manage their weight through diet and exercise.
The Weighty Issue of Obesity
"In just one generation, we have gone from the majority of people in the United States being of normal weight to more than two thirds of the population being overweight, and a significant portion of people are obese," said Jennifer A. Ligibel, MD, chair of the ASCO Energy Balance Work Group, assistant professor at Harvard Medical School, and senior physician of adult oncology at Dana-Farber Cancer Institute, Boston, Massachusetts.
Over the past 25 years, the average weight of Americans has increased by a range of 20-40 lb, she said.[6,7] Obesity differs by race and ethnicity. Rates are higher in women and especially in adult African American women, 46% of whom are obese. Cancer disproportionately affects obese people, she noted.
National Cancer Institute's SEER data estimated that about 84,000 new cases of obesity-related cancers were diagnosed in 2007. Four percent of cancers in men and 7% of cancers in women were directly attributable to obesity.
Obesity is prevalent in cancer survivors, and it is associated with an increased risk for mortality. A study of almost 1 million adults showed that those who weighed more had cancer mortality rates that were 50%-60% higher than their normal-weight counterparts. Death rates were increased across the board in most types of cancers.
Investigators also constructed models and estimated that if the current trends continue over the next 20 years, at least 500,000 cancers attributable to obesity will be diagnosed in the United States; if every adult in the United States decreased his or her weight by 2.5 lb (ie, 1 unit of BMI), 73,000-127,000 fewer cancers would occur.
Physical activity is known to help maintain weight and is associated with improved health, yet only about one third of all cancer survivors met the goal of at least 3 hours of moderate physical exercise per week in a large cross-sectional survey of more than 9000 cancer survivors.
"This has been shown in cancer patients as well," Dr Ligibel said. "Clearly, more work needs to be done to get cancer patients to manage their weight, eat healthier diets, and engage in physical activity."
Cancer Diagnosis: Taking Advantage of a Teachable Moment
Getting cancer patients to manage their weight and eat healthier diets is achievable, and the first step is for oncologists and oncology health professionals to approach the issue of weight control with their patients, said Wendy Demark-Wahnefried, PhD, RD, professor and Webb Endowed Chair of Nutrition Sciences, and associate director for Cancer Prevention and Control at the University of Alabama Comprehensive Cancer Center, at Birmingham.
"A cancer diagnosis is a teachable moment," she explained. A recent study of cancer survivors reported that 40% adopted healthier eating habits, 35% made attempts to lose weight, and 29% started exercising after their diagnosis.
"But those effects tend to be temporary and patients need reinforcement," she continued. "In the same study, 92% of survivors said that they prefer to receive guidance from their oncologist while receiving cancer care. If they don't get feedback regarding their weight, they often assume they are okay. Not saying something about their weight—if they are overweight or obese—may give them the green light to remain that way."
Obesity is a complex problem that is the result of the confluence of many factors, and it is now considered a disease, Dr Demark-Wahnefried noted. Barriers to addressing obesity in clinical practice include time and expertise to deliver effective advice. Many resources are out there, including an ASCO position paper that describes practical clinical interventions for diet, physical activity, and weight control in cancer survivors, written by Dr Ligibel, Dr Demark-Wahnefried, and colleagues.
Several websites of various organizations provide materials on obesity and weight management for clinicians and patients, including ASCO, the Academy of Nutrition and Dietetics, the American Institute of Cancer Research, American Cancer Society, and the National Heart, Lung, and Blood Institute.
Revised guidelines jointly issued by the American College of Cardiology, American Heart Association Task Force, and the Obesity Society state that as little as a 3% loss of body weight is associated with health benefits in high-risk groups. The recommendations include: up to 2 lb per week weight loss for overweight and obese people; and energy restriction to 1200 and 1800 kcal/day for women and for men, respectively. These revised guidelines do not endorse the distribution of dietary fat and carbohydrates, because studies show equivocal results with either approach, with the exception of improvements in serum triglycerides, which appear superior with the low-carbohydrate diet. Guidelines also stress the importance of self-monitoring by weighing oneself every day and keeping a food and exercise log journal.
The cornerstones of weight loss are diet, physical activity, and lifestyle modification. Reducing calories is the best way to lose weight, and physical activity maintains weight loss and prevents weight gain.
"Always start with diet and lifestyle modification, but if patients fail and are morbidly obese, pharmacotherapy and surgery may be options," she suggested.
There are some systematic reviews of weight loss, mainly in breast cancer survivors. One review of 14 trials ranging in duration from 2 to 18 months found that 57% of trials promoted weight loss of 5% or more, and patients who met that benchmark had clinically significant benefits in hemoglobin A1c, insulin, inflammatory markers, lipids, blood pressure, physical function, and quality of life.
Other trials of weight loss in breast cancer survivors found essentially the same effects, Dr Demark-Wahnefried noted. "These trials show that weight loss is possible and does provide benefits," she said.
Assessing Willingness to Undertake Weight Loss
Oncologists and advanced practitioners can promote weight loss in cancer survivors by following the 5 A's approach, which has proved successful in getting people to stop smoking.
The five A's are: ask, advise, assess, assist, and arrange. Even if oncologists just ask and advise, that will be a step forward. Dr Demark-Wahnefried elaborated as follows:
Ask. Be sure to ask patients if they know about the importance of weight management for their overall health. Ask them, "Have you heard about the relationship between body weight and cancer?" Inform them that we know obesity is associated with poor prognosis in some cancers. Weight is also associated with prevalent comorbidity, such as heart disease and diabetes.
Advise. This is very important and is the one step that is essential. Orient patients by using a BMI chart. This makes the discussion focused on a piece of paper, and not on the patient, during what can be a difficult discussion. Set incremental goals that are achievable, not ones that can be overwhelming, such as the loss of 2 lb per week rather than a 50-lb weight loss.
Assess. Gauge the patient's willingness to pursue weight loss. Ask questions such as, "Have you tried to lose weight before? How successful were you? How do you feel about getting your weight under control now by watching what you eat and exercising more?" Dr Demark-Wahnefried added, "Some patients will want to do this, but other patients will say that this is not a good time. If the patient is not ready, you have to accept that and plant the message regarding the importance of weight loss. Then continue to reassess during future appointments."
Assist. If the patient is ready, some simple messages can be delivered, such as setting a start date to begin weight loss with incremental goals. The oncologist can also provide brochures and suggest selected websites. However, given limitations on time and resources, most oncologists may be more successful by arranging referrals.
Arrange. Referral to a registered dietitian, especially one with certified specialization in oncology (CSO), can provide expert individual care.
"Reinforce success," Dr Demark-Wahnefried emphasized. "Your patients count on you to notice their progress. Praise their weight loss. If you don't, the patent is likely to regress."
The Data on Physical Activity and Outcomes
Although there are more than 200 interventional trials of physical exercise in cancer patients, no randomized trials have shown an effect on disease progression and survival. Most of the evidence in support of physical exercise comes from systematic reviews of trials conducted in the active treatment phase and survivorship phase, explained Kerry Courneya, PhD, director of the Behavioral Medicine Laboratory, and Canada Research Chair in Physical Activity and Cancer at the University of Alberta, in Edmonton, Canada. Little research has been done in the palliative phase or pretreatment phase.
"The effects of physical exercise seem to be larger in the survivorship phase," Dr Courneya told attendees of the special session.
Systematic reviews of observational studies have been conducted on the effect of physical exercise on survival, looking at different types of exercise, such as aerobic or resistance training, and on specific outcomes, the most common one being the effect on fatigue.
The types of intervention studies that have been done include efficacy trials, with a specific focus on health outcomes; behavior change trials, focusing on behavior as a specific outcome, and usually testing telephone- and Internet-based interventions, which appear to be cost-effective.
"On the positive side, many of these interventions are feasible and can be rolled out in oncology practice," said Dr Courneya, "but the downside is that it is a struggle to change exercise behavior, let alone outcomes, and the evidence to date is not encouraging that these interventions can change behaviors sufficiently to affect outcomes."
"Effectiveness trials and pragmatic trials that try to change outcomes with a practical intervention have the best shot at being incorporated into clinical practice," he added.
The literature shows that outcomes are improved with supervised interventions, but it is not clear that these will find a place in clinical practice, Dr Courneya commented. "This creates a disconnect between what works and what is feasible."
Studies in depression, fatigue, and quality of life in cancer survivors all show negligible effects with unsupervised interventions and significantly improved results with supervised interventions.
When supervised interventions can no longer be maintained, it may be possible to transition to more distance-based interventions, such as telephone counseling. In fact, 69% of studies that targeted physical activity alone with telephone counseling report significant improvement post-intervention, while only 22% of trials that target both physical activity and diet reported significant improvement in physical activity post-intervention. These findings suggest that combining exercise and nutrition may dilute exercise outcomes, Dr Courneya noted.
Supervised Intervention Is Key
The field is further frustrated by a variation in findings. Studies of physical activity alone show large, moderate, small, and negligible effects on changing behavior. Seven out of 10 studies that focused on both physical activity and diet had small or negligible effects, he noted.
"The struggle is to change behavior, and even if you get some exercise behavior change, it doesn't necessarily translate to improved outcomes," Dr Courneya said. "From the data so far, you get out of exercise what you put in in terms of supervision," he emphasized.
One of the most successful behavioral intervention trials is the Diabetes Prevention Program/Look AHEAD trial. This study suggests strategies to support behavior change that can be adapted for cancer patients. Key elements include face-to-face sessions with qualified staff, supervised exercise sessions, setting clear and challenging exercise goals, following behavior modification techniques, providing intensive and ongoing contact, written materials to supplement spoken advice, individual tailoring of intervention, and a theoretical mode of behavior change.
To evaluate similar strategies in cancer patients, Dr Courneya and colleagues are leading the CHALLENGE trial. The study will evaluate the effects of a 3-year exercise program on disease-free survival in survivors of stage II-III colorectal cancer. This trial incorporates a colon cancer–specific exercise guidebook; supervised exercise sessions; 14 face-to-face counseling sessions; telephone counseling sessions; tapering contact (weekly to biweekly to monthly); and free/low-cost access to a fitness facility. The authors have demonstrated the feasibility of this approach, and the study is ongoing.
"Recommend exercise to your patients. Provide written exercise materials. Support exercise research studies if available," advised Dr Courneya.
"There is good evidence suggesting that physical exercise improves outcomes in cancer patients, but it needs to be appropriately prescribed and delivered. Supervised programs seem to be the best way of prescribing and delivering exercise. Research is ongoing to find more cost-effective ways to deliver these interventions," he stated.
ASCO's Advocacy Against Obesity
The ASCO Initiative on Obesity was launched in 2014 to reverse the disturbing and dangerous trends toward obesity. The initiative has four goals: (1) to increase awareness of the link between obesity and cancer; (2) to provide oncologists and clinicians with resources and tools; (3) to support research on the impact of weight loss and lifestyle change on cancer risk and outcomes; and (4) to advocate for policies that support healthy lifestyles in cancer patients.
The group has made major inroads in addressing the first three goals. The ASCO Obesity Toolkit, released last May, provides information on the link between obesity and cancer and tips for oncologists. Materials are available in English, Spanish, and French, in hard-copy and electronic versions.
"This information can be incorporated into electronic health records and printed out for patients," Dr Ligibel suggested.
A position statement was published on the Obesity Initiative in the fall of 2014 in the Journal of Clinical Oncology.
A research summit was convened last fall to advance the effort to conduct obesity clinical trials in cancer survivors. The goal was to identify the most pressing questions to be addressed by research and to develop a roadmap for developing, implementing, and funding trials that could determine whether weight loss or increased exercise could reduce the risk for cancer recurrence and improve survival in cancer populations. A manuscript is in development summarizing proceedings of the summit.
Advocating for policies—the fourth goal of the initiative—will require a broader effort that engages industry, foundations, and medical societies in partnership to effect meaningful changes via education, research, and policy, Dr Ligibel explained.
"ASCO has started a joint working group with the American College of Cardiology, and we will seek partnerships with other groups and cancer organizations," she said.
A second research summit is planned to accelerate obesity research through interdisciplinary collaboration. This summit will address ways that groups can work together to answer common questions, such as how to help people lose weight and maintain weight loss over time.
Medscape Oncology © 2015 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: 'The Skinny' on Obesity, Cancer, and Losing Weight - Medscape - Jul 09, 2015.