What is Obesity?

The definition of obesity varies depending on what one reads. In general, overweight and obesity indicate a weight greater than what is considered healthy. Obesity is a chronic condition defined by an excess amount body fat. In another word, obesity, in fairly simple terms, excess body weight resulting from eating too much and exercising too little, due in large part to a lack of willpower or self-restraint.

Height-weight tables indicating "ideal" weight have been in use since 1959 but have their shortcomings. A newer measure of obesity that is gaining in popularity among researchers and clinicians is the body mass index (BMI). BMI is the body weight in kilograms divided by the square of the height in meters ([weight in kg] ÷ [height in meters] 2). Since BMI describes body weight relative to height, it is strongly correlated with total body fat content in adults. An adult who has a BMI of 25-29.9 is considered overweight, and an adult who has a BMI over 30 is considered obese. BMI does not actually measure body fat, but generally correlates well with the degree of obesity. The categories of obesity developed by the World Health Organization are:

• BMI 25 to 29.9 - Grade 1 obesity (moderate overweight)
• BMI 30 to 39.9 - Grade 2 obesity (severe overweight)
• BMI > 40 - Grade 3 obesity (massive/morbid obesity).

Using a BMI table, a person 5'6" tall weighing 140 pounds would have a BMI of 23, well out of the range of risk. That same 5'6" person weighing 190 pounds would have a BMI of 31, in the range of Grade 2 obesity.

A BMI of 27 or higher is associated with increased morbidity and mortality; this is generally considered the point at which some form of treatment for obesity is required. A BMI between 25 and 27 is considered a warning sign and may warrant intervention, especially in the presence of additional risk factors.