What BMI Indicates Obesity?

Doctor and patient

Do you know your BMI? | Gpointstudio/iStock/Getty Images

First of all — what is my BMI?

Your Body Mass Index, or BMI, is a calculation of your fat based on the relationship between your weight and height. The higher your BMI, the riskier it is you’ve fallen into the overweight or obese territory. While many people focus on the number on the scale, few know their BMI until their visit with a general practitioner.

Your BMI is important for a number of reasons. If your BMI is out of the healthy range for your height, your health risks may increase significantly. It’s a good indicator of the “average” you want to reach, however, it can be occasionally misleading, such as with an extremely muscular person who has a high BMI.

BMI values don’t account for age, sex, ethnicity, or muscle mass, but it’s efficient due to its simple, inexpensive, and noninvasive ability to measure body fat.

The official definition of obesity

Obesity is a condition where a person has accumulated so much body fat that it could have a negative effect on their health. Your BMI can indicate if you’ve transcended a “normal” weight for your height into overweight territory or obesity. A body weight that’s 20% or higher (BMI of 30 or over) than the standard level for a given height is considered obese. A BMI of 25 to 29.9 is considered overweight in most people.

Here is how to calculate your BMI and your health

BMI or Body Mass Index Infographic Chart

Use BMI calculators and consult a doctor or nutritionist before drastically changing your diet. | bearsky23/Getty Images

The Centers for Disease Control and Prevention (CDC) suggest using their adult BMI calculator to determine your BMI or use their index chart. Your BMI is measured by your weight in kilograms divided by the square of your height in meters.

  • Underweight range: BMI of 18.5 or less
  • Normal range: 18.5 to <25
  • Overweight range: 25.0 to <30
  • Obese range: BMI of 30.0 or higher

Obesity is frequently subdivided into categories:

  • Class 1: BMI of 30 to < 35
  • Class 2: BMI of 35 to < 40
  • Class 3: BMI of 40 or higher. Class 3 obesity is sometimes categorized as “extreme” or “severe” obesity.

Remember that while your BMI can be used as a screening tool for obesity, it should not be used as a diagnostic tool.

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