Definition of Obesity

There are several definitions of obesity: some are technical, some are for common use and some based on demography.

A conventional definition of obesity involves BMI, a key index for relating body weight to height, which is a person's weight in kilograms (kg) divided by their height in meters squared.

BMI is used because, for most people, it correlates with their amount of body fat.

Definition of obesity as by the National Institutes of Health:

According to National Institute of Health, obesity is a condition where Body Mass Index (BMI) of a person goes beyond 30.  

Definition of obesity as by American Obesity Association (AOA):

AOA defines obesity as a complex, multifactorial chronic disease that develops from an interaction of genotype and the environment. American Obesity Association’s definition of obesity adds a note that their understanding of how and why obesity develops is incomplete, but involves the integration of social, behavioral, cultural, physiological, metabolic and genetic factors.

Definition of obesity by Centers for Disease Control and Prevention (CDC):

CDC determines overweight and obesity ranges, using weight and height to calculate the body mass index (BMI). According to CDC’s definition of obesity, an adult is obese if he or she has a BMI of 30 or higher and can be considered overweight if he or she has a BMI between 25 and 29.9.

Definition of obesity as adopted by World Health Organization (WHO):

WHO’s definition of obesity is based on weight classifications. Like National Institutes of Health (NIH), these weight categories are also based on BMI.  

Definition of obesity as grabbed from a leading online dictionary (the freedictionary.com):

“Obesity is an increase in body weight beyond the limitation of skeletal and physical requirements, as a result of excessive accumulation of body fat.”

Children’s Hospital, University of Chicago gives definition of obesity as a generalized accumulation of body fat.

Definition of obesity as on weight.com:

Dr. Michael D. Myers defines obesity as an excess of body fat that frequently results in a significant impairment of health. According to him, obesity is as a result of increase in the size and number of fat cells. First of all, there is increase in the size of these fats cells and thereafter the number of fats cells.

Dr. Arya Sharma of the University of Alberta notes that though the conventional definition of obesity is based on Body Mass Index (BMI), but not everyone with an increased BMI can be classified as high risk. He further notes that weight loss can be beneficial for people with lower BMI. So, BMI should not be the only parameter while forming a definition of obesity.