Researcher explores how the “obesity paradox” influences cancer outcomes
By Jon Weiner
Bette Caan, DrPH, is a cancer epidemiologist at the Kaiser Permanente Northern California Division of Research who focuses on the role of diet, physical activity, and body composition factors in the progression of cancer.
Q: If you had to think back, is there a single moment in your life that sparked your interest in what you’re doing now?
It was about 10 years ago. Scientists and clinicians were concerned about weight gain in breast cancer survivors and the effect it would have on cancer recurrence and death. The viewpoint at the time was that since being overweight or obese was bad for women who had breast cancer, then weight gain after a diagnosis must also be bad. But I had a data set of breast cancer survivors which showed that breast cancer survivors who gained weight had no worse outcomes, and in fact, those who lost weight were the ones that did the worst. I was trying to figure out why when I met a woman — now a colleague on my research — who studied cancer cachexia, a condition that leads to muscle loss in patients with cancer. She asked if I ever thought about whether those women who lost weight had sarcopenia, the term for patients with low muscle mass. She told me about a new method to study body composition using CT scans, and that became a turning point in my career. I later went on to get two research grants, one for breast cancer and one for colorectal cancer, to study sarcopenia and cancer outcomes.
Q: What should people know about their health, in your area of expertise, that you don’t think they know, and should?
We know that being overweight or mildly obese might be related to getting certain cancers, but being overweight or mildly obese may be related to better outcomes once patients have those cancers. This is known as the obesity paradox.
Q: What are you and other researchers learning about the role of muscle mass in cancer outcomes?
I think the study of muscle mass in cancer outcomes is important because it has largely been ignored in favor of studying adiposity, or obesity. Yet skeletal muscle is the most abundant tissue in the body, making up about 40 percent of our body mass. More importantly, muscle secretes hundreds of myokine peptides that influence insulin sensitivity, inflammation, immune function, fat oxidation, and whole-body metabolism, among other aspects. Muscle mass has important independent effects on colorectal cancer outcomes, and about a third of newly diagnosed nonmetastatic colorectal cancer patients are at risk due to sarcopenia.
Q: March is Colorectal Cancer Awareness Month. How has cancer research changed over the decades? Where do you see it headed in the future?
The field has changed significantly due to our ability to use CT scans to measure muscle mass to identify those with sarcopenia. Right now, it is done only for research purposes but in the future, I hope the assessment will be automated. Then, the presence or absence of sarcopenia for every cancer patient who has a diagnostic CT scan can be entered into their patient record automatically, allowing it to be a factor for treatment decisions such as chemotherapy dosing and surgery risk considerations.
Q: In your free time, what do you like to do?
I love to hike, travel, go to country music concerts, and hang out with my family.