Physical Activity, Fitness and the Energy Cost of Activities: Implications for Obesity in Children and Adolescents in the Tropics - Advances in Food and Nutrition Research - page 54

Organization (WHO), 2013 ) . While a variety of terms and cut-off points
have been proposed and used to describe overweight and obesity in children
and adolescents, there is considerable argument as to whether these classifi-
cations are applicable for these young populations.
Ideally, the classifications of overweight and obesity should be defined on
the basis of whole-body fatness ( Cole, Bellizzi, Flegal, &Dietz, 2000 ) , which
can be directly measured using several methods, such as densitometry, mag-
netic resonance imaging, and bioelectrical impedance analysis ( Dehghan
et al., 2005 ) . However, these methods are usually time consuming and
require good cooperation of the subject, which makes it impractical for
use in large population-based surveys that involve children and adolescents.
Moreover, these measurements are relatively expensive and thus not widely
available in most of the developing countries where resources are limited.
Most importantly, established criteria or cut-off points for defining excess
fatness in children and adolescents who are overweight or obese are still
lacking ( Flegal & Ogden, 2011; Krebs et al., 2007 ).
Because of these limitations, anthropometric measurements (skinfold
thickness, waist circumference, BMI, and waist-to-hip ratio) are often used
as surrogates for body fatness ( Rao, 2012 ) . Among these measurements,
BMI, which is derived from height and weight measures, has been found
to be the most useful indicator of increased body fat. Therefore, BMI is rec-
ommended for evaluating overweight and obesity in children and adolescents
in the clinical setting ( Barlow& Committee, 2007; Daniels, 2009 ). However,
the interpretation of BMI in these young populations is complicated by body
size and composition changes during growth, and the failure of BMI in dis-
tinguishing fat from fat-free mass (FFM) may lead to misclassifications of indi-
viduals with larger muscle masses ( Daniels, 2009; Dehghan et al., 2005 ).
Moreover, there is still no precise definition of overweight and obesity based
on BMI, and the selection of these BMI cut points are generally statistical
rather than risk based ( Flegal & Ogden, 2011 ). Therefore, the interpretations
and comparisons of the BMI distributions should be performed cautiously,
particularly those between countries that have used different reference data
sets for BMI. It is also of practical importance to clearly define the terminology
of overweight and obesity in the context of children and adolescents, given
that the prevalence rates of these conditions are rising at an alarming rate.
2.2. Health consequences of overweight and obesity
Overweight and obesity in childhood and adolescence are known to have
serious adverse consequences on both physical and psychological health.