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Table 8: Classification of overweight in adults according to BMIa

Classification BMI (kg/m2) Risk of comorbidities
a These BMI values are age-independent and the same for both sexes. However, BMI may not correspond to the same degree of fatness in different populations due, in part, to differences in body proportions. The table shows a simplistic relationship between BMI and the risk of comorbidity, which can be affected by a range of factors, including the nature and the risk of comorbidity, which can be affected by a range of factors, including the nature of the diet, ethnic group and activity level. The risks associated with increasing BMI are continuous and graded and begin at a BMI below 25. The interpretation of BMI gradings in relation to risk may differ for different populations. Both BMI and a measure of fat distribution (waist circumference or waist: hip ratio (WHR)) are important in calculating the risk of obesity comorbidities.
Underweight <18.5 Low (but risk of other
clinical problems increased)
Normal range 18.5-24.9 Average
Overweight ≥25.0  
Pre-obese 25.0-29.9 Increased 
Obese class I 30.0-34.9 Moderate
Obese class II 35.0-39.9 Severe
Obese class III ≥40 Very severe

Source: WHO/FAO "Diet, Nutrition and the prevention of chronic diseases"
Section 5.2.6 Disease-specific recommendations 

Related publication:
Diet & Nutrition homeDiet and Nutrition Prevention of Chronic Diseases
Other Figures & Tables on this publication:

Table 1: Global and regional per capita food consumption (kcal per capita per day)

Table 2. Vegetable and animal sources of energy in the diet (kcal per capita per day)

Table 3: Vegetable and animal sources of energy in the diet (kcal per capita per day) Supply of fat (g per capita per day)

Table 4. Per capita consumption of livestock products

Table 6. Ranges of population nutrient intake goals

Table 7: Summary of strength of evidence on factors that might promote or protect against weight gain and obesitya

Table 8: Classification of overweight in adults according to BMIa

Table 9: Summary of strength of evidence on lifestyle factors and risk of developing type 2 diabetes  

Table 10: Summary of strength of evidence on lifestyle factors and risk of developing cardiovascular diseases  

Table 11: Summary of strength of evidence on lifestyle factors and the risk of developing cancer  

Table 12: Trends in levels of dental caries in 12-year-olds mean [number of] delayed, missing, filled permanent teeth (DMFT) per person aged 12 years [as a result of carries]

Table 13: Prevalence of toothlessness (edentulousness) in older people throughout the world

Table 14: Summary of strength of evidence linking diet to dental caries

Table 15: Summary of strength of evidence linking diet to dental erosion

Table 16: Summary of strength of evidence linking diet to enamel developmental defects

Table 17: Summary of strength of evidence linking diet to periodontal disease

Table 18: Summary of strength of evidence linking diet to osteoporotic fractures

Figure 3: Trends in the supply of vegetables, by region, 1970-2000

Figure 4: Ranges of population nutrient intake goals

Figure 2. Calories from major commodities in developing countries

Comment

Degrees of evidence by the Joint WHO/FAO Expert Consultation