Obesity classification

 So obesity classes

Category     BMI (kg/m2)

 Underweight      < 18.5

 Normal weight  18.5 – 24.9 

Overweight        25.0 – 29.9

 Obese (class I)    30.0 – 34.9

 Obese (class II)    35.0 – 39.9

 Obese (class III)   ≥ 40.0

Obesity is typically defined as a substantial accumulation of  body fat  that could impact health.[29]  Medical organizations tend to classify people as obese based on  body mass index (BMI) – a ratio of a person's weight in  kilograms  to the  square  of their height in  meters. For adults, the  World Health Organization  (WHO) defines  overweight  as a BMI 25 or higher, and obese  as a BMI 30 or higher.[29]  For children, obesity measures take age into consideration along with height and weight. For children aged 5–19, the WHO defines obesity as a BMI two  standard deviations  above the  median  for their age (a BMI around 18 for a five-year old; around 30 for a 19-year old).[29][30]  For children under five, the WHO defines obesity as a weight three standard deviations above the median for their height.[29]  The U.S.  Centers for Disease Control and Prevention  (CDC) further subdivides obesity based on BMI, with a BMI 30 to 35 called class 1 obesity; 35 to 40, class 2 obesity; and 40+, class 3 obesity.

 It further evaluated in terms of fat distribution via the  waist–hip ratio  and total cardiovascular risk factors.[32][33]  BMI is closely related to both  percentage body fat  and total body fat.

 In children, a healthy weight varies with age and sex. Obesity in children and adolescents is defined not as an absolute number but in relation to a historical normal group, such that obesity is a BMI greater than the 95th  percentile.[35]  The reference data on which these percentiles were based date from 1963 to 1994, and thus have not been affected by the recent increases in weight.

Some modifications to the WHO definitions have been made by particular organizations.[37]  The surgical literature breaks down class II and III or only class III obesity into further categories whose exact values are still disputed.[38] 

Any BMI ≥ 35 or 40 kg/m2  is  severe obesity.

 A BMI of ≥ 35 kg/m2  and experiencing obesity-related health conditions or ≥ 40 or 45 kg/m2  is morbid obesity.

 A BMI of ≥ 45 or 50 kg/m2  is  super obesity.

 As Asian populations develop negative health consequences at a lower BMI than  Caucasians, some nations have redefined obesity; Japan has defined obesity as any BMI greater than 25 kg/m2[14]  while China uses a BMI of greater than 28 kg/m2.[37]

 Effects on health 

Excessive body  weight  has a strong link to many  diseases and conditions, particularly cardiovascular diseases,  diabetes mellitus type 2,  obstructive sleep apnea, certain types of cancer,  osteoarthritis,[2]  and  asthma.[2][39]  As a result, obesity has been found to reduce  life expectancy.[2]

 Mortality