Obesity, Addiction, and Personalized Medicine
Future treatments for obesity will be individualized and based on cause
Posted Sep 16, 2013
Obesity is a major public health problem in the U.S. More than a third of individuals in our country are obese. Obesity substantially increases risks for a variety of medical disorders, including type 2 diabetes, sleep apnea, asthma, high blood pressure, cardiac illnesses, osteoarthritis, and cancer. Obesity is estimated to cost the U.S. economy about 150 billion dollars per year in healthcare costs and lost productivity.
Dr. Mark Gold, chair of Psychiatry at the University of Florida, and his colleagues have championed the concept that certain eating behaviors have characteristics that are similar to addictive behaviors. In fact, they suggest that some types of food can be addictive in specific individuals and that these foods influence the same brain systems that are usurped and re-programmed by addictive drugs. Dr. Gold and others have studied obesity in animals and humans and have generated data that support this concept. But does this mean that everyone who is obese is addicted to food? This seems unlikely. In fact, Dr. Gold and colleagues are not suggesting that all obese people are food addicts. Rather, they see food addiction as one of several causes for obesity.
We are intrigued by the idea that there is a subgroup of obese individuals who have features reminiscent of an addiction to sugars and perhaps other components of food. In this subgroup of individuals, consumption of certain foods may alter brain regions responsible for motivational behaviors in a manner parallel to the effects of nicotine, alcohol, marijuana, stimulants, and opiates. In this subgroup of people, food becomes a primary focus of daily activities. These individuals find comfort in food and appear to develop a type of withdrawal syndrome when they are without food for relatively short periods of time. Eating becomes a way of life and necessary for feeling okay. Over time, food loses its ability to provide pleasure; instead, it becomes necessary to prevent feeling bad. Some individuals chronically overeat; others binge. They continue their marked overeating behaviors even when obesity-related medical consequences develop. These features are not unlike some effects of addictive drugs.
Thus, some people who are obese may have a type of food addiction. We would caution that this hypothesis is not yet proven, and it remains unclear whether “compulsive” consumption of food has the same effects as addiction to opiates, cocaine, or alcohol, agents that are known to have very profound actions on brain motivation and reward circuits. The same can be said of other behaviors that are likened to “addictions,” including sex, gambling, and internet use.
For many individuals, the drive to overeat results from factors unrelated to a possible food addiction. Food is a fuel necessary for survival, and our brain is the most energy-intensive organ in the body, requiring about 20% of cardiac output to function. Mother Nature has developed a variety of mechanisms to regulate fuel (i.e., food) consumption and to make sure that the brain receives its required allotment. A number of body-produced proteins (and other chemicals) interact with body tissues like fat, liver, and brain to regulate eating behaviors. Sometimes, one or more of these chemicals gets out of balance. This dysregulation may be subtle, but over time a slight imbalance in our food intake leads to many pounds of added weight.
Other mechanisms also contribute to obesity. Specific brain regions regulate emotions, which trigger various behaviors including eating. The relationships between emotional systems and appetite systems are complex and varied. For example, some individuals who develop clinical depression lose their appetites and lose weight while other depressed individuals increase their food consumption and gain substantial weight. Thus, emotional systems interact with fuel (food) regulating systems in a manner that can lead to obesity (or starvation). We don’t yet understand the factors that predispose specific depressed individuals to weight gain or loss.
Weight gain can also occur as a side effect of medications. For example, medications used to treat psychotic symptoms or symptoms of severe mood dysregulation (such as occurs in bipolar disorder) can cause weight gain. The mechanisms underlying medication-induced weight gain are not well understood.
We have mentioned a few of the causes related to overeating and weight gain. There are many others. So, what does this all mean with respect to treatments?
Tools will become increasingly available to help define the specific causes of obesity in individual persons. These tools will likely include blood tests, genetic screens, and brain imaging procedures. Once specific causes are identified, a personalized treatment approach can be designed. Some treatment modalities may help multiple causes of obesity, while others will be effective only in individuals with specific causes. For example, if an individual is truly addicted to certain foods, then behavioral and pharmacologic treatments used to treat other addictions might be helpful. There are studies demonstrating that medications that help decrease craving for addictive drugs might help diminish craving for food in persons with behavior suggestive of food addiction. Similarly, if emotional dysregulation is closely tied to a person’s eating behavior, then targeted behavioral therapies could help the person regulate stress responses in more productive ways. If certain proteins that regulate food intake are overactive, medications could be developed to dampen the effects of those proteins. Importantly, obesity is a highly heterogeneous condition and no one treatment, including bariatric surgery, is likely to be effective in all cases.
Understanding obesity and developing effective treatments for it depend on research that spans several medical specialties including endocrinology, addiction medicine, and psychiatry. Obesity and addiction are two disorders that severely hurt the health of our country. Research is essential if we are to improve treatments and outcomes. Investing in research could save substantial money in the long run.
This column was written by Eugene Rubin MD, PhD and Charles Zorumski MD.