Childhood Obesity: Are We All Speaking the Same Language?

Abstract

Terminology and measures used in studies of weight and adiposity in children can be complex and confusing. Differences arise in metrics, terminology, reference values, and reference levels. Most studies depend on body mass index (BMI) calculated from weight and height, rather than on more direct measures of body fatness. Definitions of overweight and obesity are generally statistical rather than risk-based and use a variety of different reference data sets for BMI. As a result, different definitions often do not give the same results. A basic problem is the lack of strong evidence for any one particular definition. Rather than formulate the question as being one of how to define obesity, it might be useful to consider what BMI cut-points best predict future health risks and how efficiently to screen for such risks. The answers may be different for different populations. In addition, rather than depending solely on BMI to make screening decisions, it is likely to be useful to also consider other factors, including not only race-ethnicity, sex and age, but also factors such as family history. Despite their limitations, BMI-based definitions of overweight and obesity provide working practical definitions that are valuable for general public health surveillance and screening.

The Crisis of Obesity

“…Given the above, children and adolescents can be defined as overweight or obese using a variety of BMI reference cut-offs [6,18]. It should be pointed out that the cut-offs which are used to define overweight and obesity in children and adolescents are based purely on statistical information, and do not make reference to health risk, whereas, as has been mentioned above, the cut-offs defining obesity and overweight among adults are linked to health risk [22][23][24].…”

“…This process allows comparisons of the BMI across different ages and by gender [18]. Both BMI z-scores (also known as BMI standard deviation scores (SDS)) and BMI percentiles represent a subject's relative weight which has been adjusted according to their age and sex, and cannot therefore simply be taken as a measure of a child or adolescent's weight and height [6]. It is important to mention here that BMI z-scores and BMI percentiles can be regarded as equivalent to one another, and that each can be transformed into the other via a straightforward mathematical process.…”

“…It is important to mention here that BMI z-scores and BMI percentiles can be regarded as equivalent to one another, and that each can be transformed into the other via a straightforward mathematical process. Generally, in research applications, either BMI z-scores or BMI percentiles are used to determine cut-off values and to provide a classification of the different weight statuses of children and adolescents [6].…”

“…It is also important to note that although the rates of overweight and obesity among young children living in developed areas of the world are approximately twice the level of those in developing countries (11.7% and 6.1%, respectively), the vast majority of affected children are living in developing countries when measured in absolute terms (35 million of a total of 43 million) [5]. Perhaps surprisingly, a number of recent epidemiological studies have found that the problem of overweight and obesity extends even to children who are under two years of age [6,7]. The most important consequence of being overweight or obese during the early years of the life is the tracking of adiposity through childhood to adulthood [8].…”

“…The US can be regarded as a good example of the severity of the obesity problem in the developed world. An analysis of National Health and Nutrition Examination Survey (NHANES) data for the US between 1980 and 2008 revealed that "obesity doubled (5.0% to 10.4%) among children aged 2-5 years, tripled (6.5% to 19.6%) in children aged 6-11 years, and almost quadrupled (5.0% to 18.1%) in adolescents aged 12-19 years" [6]. It is also important to note that although the rates of overweight and obesity among young children living in developed areas of the world are approximately twice the level of those in developing countries (11.7% and 6.1%, respectively), the vast majority of affected children are living in developing countries when measured in absolute terms (35 million of a total of 43 million) [5].…”