An obese person has a substantially excessive amount of body fat for his or her height and weight. Doctors across the U.S. and the rest of the world commonly use a measurement called body mass index, or BMI, to identify people affected by obesity, as well as people in other body fat ranges. BMI calculations rely on a fairly simple formula that uses any given person’s height and weight as its main inputs. The range for simple obesity begins with a reading of 30 on the body mass index and ends with a reading of 39.9. Severely or morbidly obese people have a BMI reading of 40 or higher. In contrast, a person with a generally healthy body fat level has a BMI score that can range from 18.5 to 24.9.

Potential underlying contributors to obesity include a largely sedentary lifestyle, consumption of large amounts of high-calorie food, consumption of large amounts of alcohol, unresolved stress, smoking cessation, certain medical conditions and hormonal changes associated with menopause. Potential serious, severe or fatal consequences of obesity include the onset of type 2 diabetes, the onset of cardiovascular disease and the onset of obstructive sleep apnea.

Substance Addiction and Behavioral Addiction

Substance addiction is defined by the presence of a physical dependence on the continuing, typically inappropriate intake of alcohol or a drug or medication, as well as by the presence of related, damaging changes in behavior and the brain’s chemical ecosystem and baseline function. Chief among the relevant brain changes is an altered response to rewarding sensations in a part of the brain called the pleasure center. The American Psychiatric Association (APA) officially recognizes a range of substance-related addictions under the general heading of a condition called substance use disorder.

Behavioral addiction is defined by many of the same behavior and brain disruptions found in people dealing with substance addiction. However, instead of alcohol, drugs or medications, the source of these changes is recurring, dysfunctional participation in an activity that provides relatively harmless pleasure for most individuals. The APA made its first acknowledgement of the existence of behavioral addiction in 2013 when it created a category of conditions known as addictive disorders. Specific activities linked to the development of this condition include gambling, having sex, shopping, using the Internet and eating highly pleasurable foods.

Are There Similarities?

In the study review published in Obesity Reviews, researchers from nine institutions located in Spain, Germany and the U.S. used a re-analysis of 87 previous studies to assess the potential similarities in the brain changes associated with obesity, substance addiction and behavioral addiction. Specifically, they used data gathered from a form of real-time brain imaging called fMRI (functional magnetic resonance imaging) to see if the alterations in the brain’s reward- or pleasure-producing pathways that characterize substance addiction and behavioral addiction also appear in people affected by obesity.

When the researchers compared the brains of people dealing with obesity, substance addiction or behavioral addiction to the brains of people not dealing with any of these problems, they concluded that similar alterations in pleasure processing occur in the brains of obesity- and addiction-affected individuals, but not in the brains of the rest of the general population. They particularly noted the similarity between the pleasure-related brain reactions of obese people in the presence of food and the pleasure-related brain reactions of substance addicts in the presence of their preferred substance.

The study’s authors believe that the food-related behavior of people affected by obesity and the substance-related behavior of people affected by substance addiction may be related to the development of a similar compulsion to act. They hope that future researchers will continue to focus on the links between obesity and addiction and help develop public health strategies for reducing exposure to these widespread problems.


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