Defining morbid obesity in children based on BMI 40 at age 18 using the extended international (IOTF) cut‐offs

BACKGROUND: Studies have reported that children who are obese are becoming more severely obese. OBJECTIVE: We aimed to classify obese children based on age- and gender-specific centile curves passing through body mass index (BMI) 30, 35 and 40 at age 18 as 'class I', 'class II' or severe, and 'class III' or morbid obesity. METHODS: In addition to the International Obesity Task Force BMI cut-offs corresponding to BMI 30 and 35, we calculated the BMI cut-offs corresponding to BMI 40 using the LMS method proposed by Cole and Lobstein. We classified 217 obese children according to these criteria. RESULTS: Fifty-six (25.8%) children had class III obesity, 73 (33.6%) class II obesity and 88 (40.6%) class I obesity. Class III obese children had a higher waist circumference, systolic blood pressure and fasting insulinaemia compared with less obese children. CONCLUSION: It is clinically important to classify obese children in different classes of obesity severity.