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The New Science of Sugar Addiction by Nicole M. Avena, Ph.D.
The prevalence of obesity has increased dramatically over recent years. Currently, 1 in 2 American adults are either overweight or obese, and experts speculate that if this trend continues, by the year 2030, 86.3% of Americans will be overweight. Obesity can result in both physical and psychological challenges.
The recognized medical comorbidities of obesity include cardiovascular disease, type-2 diabetes, stroke, dyslipidemia, and osteoarthritis. This public health burden has driven many scientists and clinicians to look for a “cure” for obesity, and though we are still a long way from finding a solution, many novel approaches have been developed to tackle the issue of obesity. In particular, the new science of “food addiction” is revealing new directions for understanding obesity, which may lead us to more effective treatments.
The Connection Between Food Addiction and Drug Addiction
While the topic of “food addiction” remains controversial, scientists have found significant overlaps between the effects of overeating certain palatable foods and drugs of abuse. There are innate biological processes that occur in our brain daily which reinforce the feeding behavior as well as other behaviors that are essential for survival. For our ancestors, who spent the majority of their time hunting and gathering food in an environment where food was considerably more difficult to obtain, the drive to overeat when food was available was advantageous because they may not have always been guaranteed a next meal.
Along with overeating can come the release of neurochemicals that are associated with euphoria and pleasure, resulting in a positive reinforcement of food consumption. In the past few decades, our food environment has undergone a dramatic change with the market now saturated with highly-palatable foods that are often dense in calories but lack nutrients.
These foods are also highly rewarding, and some consider them to be hyper-palatable. Sugar, one of the most ubiquitous ingredients in many if not all highly-palatable foods, has been the focus of research in this field due to the fact that rats and humans both have a pleasurable reaction to the taste of a sugar solution. Additionally, the national statistics regarding sugar consumption are startling, with the average American consuming approximately 22 teaspoons of added sugar each day.
Addiction main phases: bingeing, withdrawal, and craving.
Data collected from studies using animal models have demonstrated both neurochemical and behavioral overlaps between the effects of overeating sugar-rich foods and what can be seen in the context of addiction to drugs of abuse. Addiction can be simplified into three main phases: bingeing, withdrawal, and craving. Bingeing is defined as increased consumption during a relatively short period of time, usually following a period of deprivation or abstinence.
When rats are given daily but intermittent access to a sugar solution, an increase in sugar intake is observed during the 1st hour of access. This behavior is thus considered bingeing and may be a sign of dependence. Further, when animals are deprived of sugar after a history of daily, intermittent access to it, they exhibit a set of behaviors, including physiological signs of distress and anxiety, that are similar to what is seen during opiate withdrawal.
Additionally, after 2 weeks of forced abstinence, these rats have been shown to press a lever 23% more than before their abstinence in order to gain access to sugar. This behavior demonstrates an enhanced motivation to obtain sugar, and thus, is evidence of craving. Rats that are prone to overeat are also willing to engage in risky behaviors in order to access sugar-rich foods, such as crossing an electrified grid to obtain candies.
Aside from these behavioral changes, there are many measurable neurochemical changes that take place when sugar is consumed in excess. For example, in laboratory animals, daily, intermittent access to sugar results in changes in the dopamine and opioid systems that are similar to what is seen in response to drugs of abuse. These changes are especially noteworthy as they occur in the parts of the brain that are responsible for reward, motivation, and pleasure.
Food addiction research is not limited to animal models. Many recent studies have begun to use the Yale Food Addiction Scale (YFAS), an assessment tool developed to measure food addiction, in clinical groups. Studies using this tool have demonstrated an association between increased food addiction scores and increased activation of brain regions that are involved in motivation when participants anticipated eating a palatable food.
Interestingly, food addiction scores are not directly correlated with body-mass index. It seems that while a significant number (up to 57% of individuals in some studies) of obese people who have comorbid binge eating disorder meet the criteria for having a food addiction according to the YFAS, people of varying weight ranges can meet this criterion. This suggests that food addiction isn’t something that is specific to obesity, but rather that it might explain overeating among many different groups.
There are important implications for public health policy when considering palatable foods in a similar light as substances of abuse. Currently, there is a remarkable resemblance between the public health directions for obesity and those seen in the past for tobacco. The increased taxation and termination of government subsidies for tobacco have resulted in increased cost and thus reduced availability. Such policy changes have proven to be effective and have resulted in significant public health gains.
The current debate on taxing sugar-sweetened beverages reflects a similar interest from public health policymakers to reduce the availability of energy-dense but nutrient-deficient foods. However, there are unique challenges with such changes because, unlike tobacco, food is essential for survival. Additionally, we are still at an early stage of identifying the addictive components of palatable foods that are known to result in weight gain. So, while we have begun to uncover a lot about the overlaps that might exist between overeating and addiction, there is still much more to learn.
Dr. Avena’s TED Talk on Sugar Addiction
She is an expert in the fields of nutrition, diet, and addiction. She has published over 60 scholarly journal articles, as well as several book chapters on topics related to food, addiction, obesity and eating disorders.
She recently edited the book, Animal Models of Eating Disorders (Springer/Humana Press, 2013), and she has a book Why Diets Fail (Ten Speed/Crown) available.
Her research achievements have been honored by awards from several groups including the New York Academy of Sciences, the American Psychological Association, the National Institute on Drug Abuse, and her research has been funded by the National Institutes of Health (NIH) and National Eating Disorders Association.
She has a blog on Psychology Today, and you can also follow her on Twitter and Facebook.
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