Abstract
AimsBody mass index (BMI) shows several limitations as indicator of fatness. Using the International Obesity Task Force (IOTF) reference and the World Health Organization (WHO) standard 2007 on the same dataset yielded widely different rates. At higher levels, BMI and the BMI cut-offs may be help in informing a clinical judgement, but at levels near the norm additional criteria may be needed. This study compares the prevalence of overweight and obesity using IOTF and WHO-2007 references and interprets body composition by comparing measures of BMI and body fatness (fat mass index, FMI; and waist-to-height ratio, WHtR) among an adolescent population.Methods and ResultsA random sample (n = 1231) of adolescent population (12–17 years old) was interviewed. Weight, height, waist circumference, triceps and subscapular skinfolds were used to calculate BMI, FMI, and WHtR. The prevalence of overweight and obesity were 12.3% and 15.4% (WHO standards) and 18.6% and 6.1% (IOTF definition). Despite that IOTF cut-offs misclassified less often than WHO standards, BMI categories were combined with FMI and WHtR resulting in the Adiposity & Fat Distribution for adolescents (AFAD-A) classification, which identified the following groups normal-weight normal-fat (73.2%), normal-weight overfat (2.1%), overweight normal-fat (6.7%), overweight overfat (11.9%) and obesity (6.1%), and also classified overweight at risk and obese adolescents into type-I (9.5% and 1.3%, respectively) and type-II (2.3% and 4.9%, respectively) depending if they had or not abdominal fatness.ConclusionsThere are differences between IOTF and WHO-2007 international references and there is a misclassification when adiposity is considered. The BMI limitations, especially for overweight identification, could be reduced by adding an estimate of both adiposity (FMI) and fat distribution (WHtR). The AFAD-A classification could be useful in clinical and population health to identify overfat adolescent and those who have greater risk of developing weight-related cardiovascular diseases according to the BMI category.
Highlights
In children and adolescents, the body mass index (BMI) for age has been established as the main measurement to define overweight and obesity, because it can be obtained and is correlated with percentage of body fat [1].Despite some discussion, in epidemiological studies is general agreement on the appropriateness of BMI to define overweight and obesity with an international standard [2]
Despite that International Obesity Task Force (IOTF) cut-offs misclassified less often than World Health Organization (WHO) standards, BMI categories were combined with fat mass index (FMI) and waist-to-height ratio (WHtR) resulting in the Adiposity & Fat Distribution for adolescents (AFAD-A) classification, which identified the following groups normal-weight normal-fat (73.2%), normal-weight overfat (2.1%), overweight normal-fat (6.7%), overweight overfat (11.9%) and obesity (6.1%), and classified overweight at risk and obese adolescents into type-I (9.5% and 1.3%, respectively) and type-II (2.3% and 4.9%, respectively) depending if they had or not abdominal fatness
The AFAD-A classification could be useful in clinical and population health to identify overfat adolescent and those who have greater risk of developing weight-related cardiovascular diseases according to the BMI category
Summary
The body mass index (BMI) for age has been established as the main measurement to define overweight and obesity, because it can be obtained and is correlated with percentage of body fat [1].Despite some discussion, in epidemiological studies is general agreement on the appropriateness of BMI to define overweight and obesity with an international standard [2]. The IOTF reference for children and adolescents 2–18 years old [3] was developed from a database of 97,876 boys and 94,851 girls from birth to 25 years from six countries (Brazil, Great Britain, Hong Kong, the Netherlands, Singapore and the USA). Centile curves were constructed using the LMS method, and BMI values of 25 and 30 at 18 years of age for boys and girls were tracked back to define BMI values for overweight and obesity at younger ages. The WHO-2007 standard for children and adolescents (5–19 years old) [4] was developed using the 1977 National Center for Health Statistics (NCHS)/WHO growth reference by addressing its limitations and linking construction to the WHO Child Growth Standards curves for children under five years old. State of the art statistical techniques were used to construct and smooth the new growth curves
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