A simple definition of obesity is being well over one’s normal body weight. A more precise definition involves something known as body mass index (BMI). BMI is an index relating a person’s weight and height and can be estimated using the following website http://www.nhlbi.nih.gov/guidelines/obesity/BMI/bmicalc.htm.
The accepted definition of obesity is a BMI greater than 30 and is distinguished from being overweight in which the BMI is greater than 25 but less than 30. Thus, obesity means someone who is more than overweight.