Understanding Youth and Adolescent Overweight and Obesity: Resources for Families and Communities

Introduction

Over the past three decades, the number of young people who are obese has nearly tripled (National Center for Health Statistics, 2006). Currently, approximately 17.4% of adolescents (ages 12-19) and 18.8% of children (ages 6-11) are considered overweight (National Center for Health Statistics, 2006). In 2004, the U.S. Institute of Medicine called the prevention of childhood obesity a national priority.

The consequences of childhood overweight and obesity are serious. Being overweight or obese increases the risk for heart problems, high blood pressure, and other medical problems (e.g., Sothern et al., 2000), and the psychological impact of being overweight can be devastating. Obesity during childhood and adolescence has been associated with higher rates of sickness and death in adulthood, even when adult weight is considered (Must, Jaques, Dallal, Bajema, & Dietz, 1992). This means that overweight kids may be putting themselves at serious risk of lifelong health problems--even more so than adults who become obese. Furthermore, childhood overweight and obesity, if not treated, can lead to overweight and obesity in adulthood (Freedman, Khan, Dietz, Srinivasan, & Berenson, 2001). Adult overweight and obesity are difficult to treat successfully over the long term (Jeffery et al., 2000), and are associated with life-threatening health problems, such as heart problems, stroke, diabetes, and high blood pressure.

Why is Obesity Increasing?

It is rare for overweight and obesity to be caused by hormonal or genetic defects (Moran, 1999). So what is causing this increase in overweight and obesity? Although the most common reason for being overweight is clear (people eat more calories in food than they burn in exercise), the reasons for the dramatic, nationwide increase in overweight and obesity in children and adolescents are unclear (Troiano & Flegal, 1998). One theory is that as our society has become more successful, convenience foods that are high in fat and calories, such as candy, chips, and sugary drinks, are produced and consumed more frequently (Goran & Treuth, 2001). Another is that our children are leading more inactive lifestyles than in the past. Rather than playing outside, children watch television, play video games, and sit at the computer (Robinson & Killen, 2001). Although our technology may be advancing, our children are sitting more and exercising less.

How is Obesity Identified and Measured?

All individuals have and need fat tissue in the body; however, when there is too much body fat, the result is obesity. Health professionals identify overweight and obesity using the Body Mass Index (BMI). BMI is calculated by measuring the proportion of weight to height. It is calculated the same way for adults and children. However, the criteria used to categorize BMI for children are age- and sex-specific and are often referred to as BMI-for-age. The Centers for Disease Control and Prevention (CDC) recommends using the terms "at risk for overweight" and "overweight" (rather than overweight and obese, which are the terms used with adults) to describe children (Centers for Disease Control and Prevention, 2006).

Calculating BMI for Adults

How do we determine who is overweight? Let's consider the example of a woman who is 5'4" and weighs 165 pounds. When we apply the formula used to compute BMI (weight (lb) / [height (in)]² x 703), we find that this woman has a BMI of 28.3. A healthy BMI ranges from 18.5 to 24.9, so the woman is considered overweight.

For adults, if a BMI score is between 25 and 29.9, a person is considered overweight. If a BMI score is 30 or above, this is deemed obesity. You can find a BMI calculator for adults online at http://www.cdc.gov/nccdphp/dnpa/bmi/adult_BMI/english_bmi_calculator/bmi_calculator.htm . A BMI calculator for children and teens is at http://apps.nccd.cdc.gov/dnpabmi/Calculator.aspx .

There are three categories of obesity. Class I obesity is defined as a BMI score of 30-34.9, and Class II obesity is defined as a BMI of 35-39.9. Lastly, Class III obesity, also known as morbid obesity or severe obesity, is defined as a BMI score of 40 or higher. Based on these numbers, as many as one-third of all Americans are considered obese.

Calculating BMI for Children and Adolescents

Now let's consider the example of a child who is 13 years old, 5'4", and weighs 180 pounds. Based on her height and weight, this child's BMI is 30.9, placing her BMI-for-age at the 98th percentile for girls her age. According to the table below, because this teen's body mass is above the 95^th percentile, she may be overweight. She should be seen by a healthcare provider for further assessment.

BMI-for-age weight status categories and the corresponding percentiles are shown in the following table.