Obesity in the World
Worldwide rates of obesity have more than doubled in the past three decades, According to the World Health Organization (WHO, 2016) approximately 1.9 billion people are classified as overweight (BMI > 25 kg/m2), and 600 million classified as obese (BMI > 30 kg/m2). The obesity crisis has been attributed to numerous environmental, genetic, behavioral, and biological factors.
Certainly genetic and epigenetic factors play a significant role in consumption of high caloric and highly palatable food choices. Moreover, the concept of addictive overeating as a medical condition is widely debated throughout the scientific community. Experts such as Kelly Brownell, PhD and I have established that behaviors or substances that increase dopamine in the midbrain and ventral stratum are potentially addictive. Highly palatable foods have been shown to increase dopamine and other neurotransmitter volume as well as hormones that mediate reward and mood in the same way as drugs of abuse. The metabolic and neuronal mechanisms that mediate hunger and satiety are not well-understood, but remain central in understanding obesity which is associated with diabetes, heart disease, cancer, high blood pressure, sleep apnea and depression. That means more visits to the doctor and increased health care costs.
Is Overeating an Addiction?
The addiction hypothesis is supported by recent neuroscientific investigation and neuroimaging studies. Experiments in animals and humans show that for some people the same reward and pleasure centers of the brain that are triggered by addictive drugs are also activated by food, especially highly palatable foods, those rich in sugar, fats and processed carbohydrates.
Like addictive drugs, highly palatable foods trigger the release of dopamine in the brain’s reward center. Once those predisposed to overeating or addiction experience the reward from eating certain foods, a neuroadaptive change and learning occurs and is repeated.
In this paper, investigators measured subjective ratings of guilt and dietary concern after manipulating female participants (N=90) to believe they had eaten more food than they actually had consumed (overeating condition), or less food than they actually consumed (undereating condition), or roughly the same (control condition) amount of palatable foods in relation to their own estimated consumption and to that of previous participants.
Rating the relative validity of a list of explanations for their eating behavior (including “the foods were really addictive”), the subjects were asked to select a snack to take home with them.
As predicted, participants in the overeating condition selected less tempting snacks than those in the undereating condition. There was also no association between food addiction attributions and snack choice. These findings suggest that perceived overeating affected snack choices but not an attribution of food addiction.
Why Does This Matter?
Many scientists now see obesity as a chronic neurobiological disease that compels overeating by usurping the brain’s reward center by the same mechanisms as addictive intoxicants. Given the increased mortality and the plethora of resources available in our calorie and fitness crazed culture, it’s hard to believe that obesity is a simple matter of choice and lack of self-control. There are hundreds of metabolic and neuropsychological factors associated with overeating and obesity. More direct research into the neuronal aspects of this deadly condition is needed.
Ruddock HK, Hardman CA. Guilty pleasures: The effect of perceived overeating on food addiction attributions and snack choice. Appetite.2018Feb1;121:9-17. doi:10.1016/2017.10.032. Epub 2017 Oct 28.