By Steve Mittelman, MD, PhD — Obesity Researcher and Pediatric Endocrinologist Children’s Hospital Los Angeles
Weight loss is typically a top New Year’s resolution. We want to get into good shape to fit into nice clothes and feel and look our best. It is well known that a better diet and exercise help us lose weight and fend off diseases like diabetes and heart disease.
There’s another disease that should make weight loss not only a New Year’s resolution, but a year-round priority for both children and adults: cancer.
Most people don’t realize that obesity causes cancer, and that obesity can decrease your odds of successfully fighting the disease if you get it. I recently spoke to a group of West Los Angeles and Santa Monica residents about obesity during a Children’s Hospital Los Angeles Ambassadors Speakers Series event at The Beach Club in Santa Monica. The Ambassador’s are a community of dedicated Children’s Hospital supporters and they had some important questions about the issue: How does body weight affect the development of cancer? Do obese people have a worse prognosis than lean patients and how can parents influence their kids to eat right and exercise to battle weight gain?
Body Weight And The Impact On Cancer
In the past decade, the medical research community began to identify the effects body weight can have on cancer. We found that obese people have an increased risk of developing cancer, and those that do, have a worse prognosis than lean people who get the disease.Together, these effects translate into an approximately 50% increased risk of dying from cancer for obese people. Overall, about 20% of all cancers in the United States can be attributed to obesity. This frightening public health concern is one that deserves more attention and research!
At Children’s Hospital Los Angeles, a team led by Anna Butturini, MD, demonstrated that obesity can also affect kids with cancer. They found that obese kids diagnosed with a blood cancer called acute lymphoblastic leukemia had a lower chance of their disease being cured by chemotherapy than lean kids. This finding is particularly chilling considering the fact that more than one in three children in the Los Angeles area is overweight or obese, and leukemia is the most common cancer in children. For these reasons, I began to study how obesity affects childhood leukemia in my lab at Children’s Hospital, and hopefully, determine how to reverse this effect.
Obesity Can Accelerate Leukemia
An obesity researcher and pediatric endocrinologist by training, I realized that obesity is not a simple disease, but represents a composite of a number of physical, physiologic, social, behavioral, genetic, and psychological effects. This makes it difficult to distinguish whether obesity has a direct effect on leukemia in kids, or perhaps is associated with another risk factor that might explain this connection. For example, people who are genetically predisposed to develop obesity might also be predisposed to develop a worse type of leukemia. However, using preclinical models, I was able to demonstrate that obesity itself directly accelerates the progression of leukemia and impairs the ability of chemotherapy to cure it.
How? It turns out there are several ways that obesity can affect cancer treatment. First, the testing of most new medications is done in relatively lean people. This means that when doctors are trying to figure out what doses work best in patients, these doses are developed in non-obese people. Doctors try to adjust for body weight and body fat in obese patients, but these adjustments are based on educated guesses, and not formally tested in clinical trials. For instance, we showed that vincristine, one of the cornerstone treatments for leukemia and a number of other cancers, accumulates in fat tissue, which can lead to under-dosing in obese patients. This could partly explain why obese patients do not do as well, if they get less effective doses of chemotherapies like vincristine.
Fat Can Fuel Leukemia
But beyond these dosing effects, we found that fat cells themselves can directly protect leukemia cells from a number of different types of chemotherapies. They do so in a few different ways. Part of this is likely through the secretion of some survival molecules, which allow the leukemia cells to resist chemotherapies. The fat cells also release fuels, like amino acids and fats, which allow the leukemia cells to better grow and divide. The fat cells may even be attracting leukemia cells to migrate into certain parts of the body, like bone marrow and fat tissue, where they are relatively protected from treatment. Together, these effects can all add up to bad news for obese patients with leukemia.
Can Weight Control Stave Off Cancer?
However, there may still be hope. My group is now looking into whether obese pediatric patients with leukemia should be put on a diet to help their prognosis. Preliminary results in preclinical models are promising, but more work needs to be done before this strategy can be taken to the clinic. In the meantime, we urge parents to work with their kids to maintain a healthy weight and lifestyle, as an important step to promote lifelong health. Some strategies we recommend are:
Changing Diet and Lifestyle
• Take sweetened beverages like sodas and juices out of the house—they are not good for you, and not good for your children.
• Encourage your kids to be physically active—enrolling them in sports and/or activities helps make this a regular part of the weekly routine.
• Model good behavior—telling your kid to exercise while you are eating a bacon cheeseburger and fries is not likely to lead to lasting changes. Exercising as a family is good for all and helps instill the importance of health into a lifetime of good habits.
• Teach your kids (and yourself) to be mindful of what you eat—visit your local farmers market and talk to the people that grow your food; try new recipes and include your kids in the preparation; eat together when possible and experience the food together—when you think about what you’re eating (as opposed to eating in front of the TV) you tend to listen to your body when it tells you you’re full!
• If your child is becoming overweight (you can calculate his/her body mass index on the CDC website at http://apps.nccd.cdc.gov/dnpabmi/), consult your pediatrician for recommendations on dietary and lifestyle interventions. Focus on decreasing calories, particularly from simple carbohydrates, increasing fiber (which is more filling), changing chips and unhealthy snacks to fruits and veggies, and being active every day.
Maintaining a healthy weight can be very difficult, but it is much easier to do when the family works together as a team!
Steven Mittelman, MD, PhD, is fellowship director in the Center for Endocrinology, Diabetes and Metabolism and director of the George Donnell Society for Pediatric Scientists at Children’s Hospital Los Angeles and an associate professor of Pediatrics and Physiology and Biophysics at the Keck School of Medicine of the University of Southern California.
