What Defines Obesity?

Obesity means that a person weighs more than what is considered healthy for their height. Body mass index (BMI) is a calculation based on height and weight that can estimate a person's total body fat and determine whether they are overweight or obese.

Obesity is a weight that is higher than what is considered healthy for a given height. 

Obesity is linked to an increased risk for many diseases, including: 

• Cardiovascular diseases 
• Heart disease 
• Stroke
• Diabetes
• Musculoskeletal disorders such as osteoarthritis 
• Some cancers
• Endometrial
• Breast
• Ovarian
• Prostate
• Liver
• Gallbladder
• Kidney
• Colon

How to Calculate BMI

Body mass index (BMI), a calculation based on height and weight that can provide an estimate of total body fat, is a tool doctors use to determine if a person is overweight, and to what degree. BMI is often used to determine whether a person is obese. 

In adults, BMI does not correlate to age. BMI is used slightly differently in children, in that it is calculated the same way as it is for adults, but then the ranges are compared to percentiles for children of the same age and sex. 

According to the Centers for Disease Control (CDC), the average American adult’s BMI was 29.6 for women and 29.1 for men, both of which are considered overweight.

BMI is calculated from the weight and square of the height:

• BMI = body weight (in kg) ÷ height (in meters) squared

Can Your BMI Be Wrong?

There are some drawbacks in using body mass index alone to determine who is obese because muscle weighs more than fat. In patients who are very muscular, such as bodybuilders or professional athletes, the BMI may overestimate body fat, which means that a person who is fit may be categorized as overweight or obese based solely on BMI measurements. Conversely, older patients who have a loss of muscle mass due to aging may have their body fat percentage underestimated.