What is the WHO obesity classification system?

Updated: Jun 09, 2021
  • Author: Osama Hamdy, MD, PhD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Although several classifications and definitions for degrees of obesity are accepted, the most widely accepted classifications are those from the World Health Organization (WHO), based on BMI. The WHO designations include the following:

  • Grade 1 overweight (commonly and simply called overweight) - BMI of 25-29.9 kg/m2

  • Grade 2 overweight (commonly called obesity) - BMI of 30-39.9 kg/m2

  • Grade 3 overweight (commonly called severe or morbid obesity) - BMI greater than or equal to 40 kg/m2

The cut-off for each grade varies according to an individual’s ethnic background. For example, a BMI of 23 kg/m2 or higher may define grade 1 overweight and 27.5 kg/m2 or higher may define grade 2 overweight (obesity) in many Asian populations, in which the risk was shown to be high and extremely high for grade 1 and 2 overweight at these levels, respectively. Other BMI cutoffs identified as potential public health action points in these populations are 32.5 and 37.5 kg/m2. [19]

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