534766
research-article2014
CPJXXX10.1177/0009922814534766Clinical PediatricsDunn-Rankin et al
Brief Report
The Obesity Quotient: A New Tool to Measure Childhood Obesity
Clinical Pediatrics 2015, Vol. 54(5) 484–486 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0009922814534766 cpj.sagepub.com
Peter Dunn-Rankin, BS, MS, MA, EdD1, Raul Rudoy, MD, MPH2, and Jerry Michael Brennan, PhD3
Introduction Obesity is a major public health problem both nationally and in Hawaii. The number of overweight/obese preschool children has doubled during the past 20 years.1 In Hawaii, yearly prevalence rates indicate that we are rapidly approaching a situation that will be difficult to reverse, particularly in certain sectors of our community where the rate of obesity is more than 35%.2 Childhood obesity has detrimental health consequences, and the earlier one can detect obesity the greater the chance that intervention can be successful. Preventing childhood overweight, by earlier identification, is crucial to the future health of any nation.3 The recommended method for identification of weight disorders is to use the body mass index (BMI). The BMI is a ratio of the weight to the squared length of the individual. High values of the BMI are commonly used to infer obesity and have been particularly useful in adults and older children. Simple modifications of the BMI such as the BMI Prime have been developed in an attempt to simplify the interpretation of BMI values. Unfortunately, BMI measures of obesity for adults cannot be effectively used with infants. Adult categories of overweight and obesity are generally but arbitrarily defined by BMIs ≥25.0 for overweight and ≥30.0 for obesity.4 Such high values, however, are rarely observed when measuring an infant’s BMI, because the relative growth rates for height and weight differ more for infants than adults. BMI values obtained early in life have not been useful in defining current obesity or predicting the development of obesity at a later age. One of the aims of this study is to introduce a new index for very young infants and to determine if the new index has a role in understanding obesity. The index, called the Obesity Quotient (OQ), is the ratio of the individual BMI value divided by the 50th percentile Criterion BMI (CBMI) for the given age. The criterion values for 15 varying percentiles are taken from the World Health Organization (WHO) tables.5 Because the OQ is based on using the WHO median BMI as the denominator in each calculation, the OQ remains almost constant over
the first 5 years of life for any given percentile. As an example, if the BMI for a 2-week-old child is 16 and the Criterion BMI is 15, the Obesity Quotient Ratio (OQ) is 16/15 or 1.067, or almost 7% over normal. The current practice of interpreting weight values in children is based on the observation of the relationship between height and weight at a specific age by calculating the child’s BMI. This value is then compared to a tabled value and the BMI percentile rank is then interpreted. We are suggesting that the new index, the OQ, is easier to interpret and compare to normal standards than the BMI. The OQ provides health care professionals with a value that represents the difference between the individual’s value and the standard value for a specific age.
Methods Sample The study material was obtained from pediatric offices from a private clinic. The population consisted of 1531 males and females born at full term and followed from birth to 5 years of age. This study was determined to be exempt from Institutional Review Board’s approval prior to review and analysis of the data.
Measures The electronic medical record was used to obtain age, height, weight, sex, and ethnicity of participants at each of the 17 076 office visits.
1
University of Hawaii at Manoa, HI, USA University of Hawaii, Honolulu HI, USA 3 Independent Practice, Honolulu HI, USA 2
Corresponding Author: Raul Rudoy MD, MPH, Department of Pediatrics, University of Hawaii, School of Medicine, 1319 Punahou Street, Honolulu, HI 96826, USA. Email: [email protected]
485
Dunn-Rankin et al A Programming Language (APL) computer program was developed to calculate the BMI and the OQ from the height and weight of the infant (www.obesityquotient. com).6 To accurately compare our data with the WHO data, the age of the child was converted to days and the height and weight were converted to centimeters and grams. The program compares the height and weight on the measurement day to the WHO criterion, also measured in days. BMI and OQ values were obtained for each office visit. Individuals were classified as underweight (BMI < 5th percentile), normal (BMI 5th-84th percentile), overweight (BMI 85th-94th percentile), obese (BMI ≥ 95th percentile), and severely obese (BMI ≥ 1.2 × 95th percentile) using the 2000 Centers for Disease Control and Prevention growth BMI categories.7
Quality Assurance Records were examined individually to detect data entry errors; 85 cases were determined to be biologically implausible and were discarded (6%). The majority of the errors were related to inaccurate measurement of height. The total final sample consisted of 1446 infants and children.
Results The frequency and related percentage of OQ values are provided and compared to the representative 15 WHO percentile periods. The calculated WHO 98th percentile corresponds to an OQ of 1.19, or 19% overweight. The WHO 84 percentile, 1 standard deviation above the mean, corresponds to an OQ of 1.07, just at the margin between Normal and Overweight categories (Table 1, columns 1 and 2). Analysis of the distribution of the 17,076 OQ values obtained from our data over the first 5 years of life demonstrated a symmetrical distribution. The percentage of OQs falling in each of the 5 general categories is comparable to the theoretical WHO percentages (Table 1, columns 5 and 6). In this comparison, the WHO distribution has a slightly larger percentage in the normal range and a slightly smaller percentage in the extremes.
Discussion The current practice of interpreting weight values in children is based on the observation of the relationship between height and weight at a specific age by calculating the child’s BMI. This value is then compared to a tabled value and the BMI percentile rank is then interpreted. Centers for Disease Control (CDC) growth
Table 1. Comparison of WHO Percentiles and Distribution With OQ Values. OQ ≥1.30 1.22 1.17 1.15 1.11 1.08 1.06 1.00 0.95 0.92 0.90 0.88 0.86 0.84 99 99 97 95 90 85 75 50 25 15 10 5 3 1
research-article2014
CPJXXX10.1177/0009922814534766Clinical PediatricsDunn-Rankin et al
Brief Report
The Obesity Quotient: A New Tool to Measure Childhood Obesity
Clinical Pediatrics 2015, Vol. 54(5) 484–486 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0009922814534766 cpj.sagepub.com
Peter Dunn-Rankin, BS, MS, MA, EdD1, Raul Rudoy, MD, MPH2, and Jerry Michael Brennan, PhD3
Introduction Obesity is a major public health problem both nationally and in Hawaii. The number of overweight/obese preschool children has doubled during the past 20 years.1 In Hawaii, yearly prevalence rates indicate that we are rapidly approaching a situation that will be difficult to reverse, particularly in certain sectors of our community where the rate of obesity is more than 35%.2 Childhood obesity has detrimental health consequences, and the earlier one can detect obesity the greater the chance that intervention can be successful. Preventing childhood overweight, by earlier identification, is crucial to the future health of any nation.3 The recommended method for identification of weight disorders is to use the body mass index (BMI). The BMI is a ratio of the weight to the squared length of the individual. High values of the BMI are commonly used to infer obesity and have been particularly useful in adults and older children. Simple modifications of the BMI such as the BMI Prime have been developed in an attempt to simplify the interpretation of BMI values. Unfortunately, BMI measures of obesity for adults cannot be effectively used with infants. Adult categories of overweight and obesity are generally but arbitrarily defined by BMIs ≥25.0 for overweight and ≥30.0 for obesity.4 Such high values, however, are rarely observed when measuring an infant’s BMI, because the relative growth rates for height and weight differ more for infants than adults. BMI values obtained early in life have not been useful in defining current obesity or predicting the development of obesity at a later age. One of the aims of this study is to introduce a new index for very young infants and to determine if the new index has a role in understanding obesity. The index, called the Obesity Quotient (OQ), is the ratio of the individual BMI value divided by the 50th percentile Criterion BMI (CBMI) for the given age. The criterion values for 15 varying percentiles are taken from the World Health Organization (WHO) tables.5 Because the OQ is based on using the WHO median BMI as the denominator in each calculation, the OQ remains almost constant over
the first 5 years of life for any given percentile. As an example, if the BMI for a 2-week-old child is 16 and the Criterion BMI is 15, the Obesity Quotient Ratio (OQ) is 16/15 or 1.067, or almost 7% over normal. The current practice of interpreting weight values in children is based on the observation of the relationship between height and weight at a specific age by calculating the child’s BMI. This value is then compared to a tabled value and the BMI percentile rank is then interpreted. We are suggesting that the new index, the OQ, is easier to interpret and compare to normal standards than the BMI. The OQ provides health care professionals with a value that represents the difference between the individual’s value and the standard value for a specific age.
Methods Sample The study material was obtained from pediatric offices from a private clinic. The population consisted of 1531 males and females born at full term and followed from birth to 5 years of age. This study was determined to be exempt from Institutional Review Board’s approval prior to review and analysis of the data.
Measures The electronic medical record was used to obtain age, height, weight, sex, and ethnicity of participants at each of the 17 076 office visits.
1
University of Hawaii at Manoa, HI, USA University of Hawaii, Honolulu HI, USA 3 Independent Practice, Honolulu HI, USA 2
Corresponding Author: Raul Rudoy MD, MPH, Department of Pediatrics, University of Hawaii, School of Medicine, 1319 Punahou Street, Honolulu, HI 96826, USA. Email: [email protected]
485
Dunn-Rankin et al A Programming Language (APL) computer program was developed to calculate the BMI and the OQ from the height and weight of the infant (www.obesityquotient. com).6 To accurately compare our data with the WHO data, the age of the child was converted to days and the height and weight were converted to centimeters and grams. The program compares the height and weight on the measurement day to the WHO criterion, also measured in days. BMI and OQ values were obtained for each office visit. Individuals were classified as underweight (BMI < 5th percentile), normal (BMI 5th-84th percentile), overweight (BMI 85th-94th percentile), obese (BMI ≥ 95th percentile), and severely obese (BMI ≥ 1.2 × 95th percentile) using the 2000 Centers for Disease Control and Prevention growth BMI categories.7
Quality Assurance Records were examined individually to detect data entry errors; 85 cases were determined to be biologically implausible and were discarded (6%). The majority of the errors were related to inaccurate measurement of height. The total final sample consisted of 1446 infants and children.
Results The frequency and related percentage of OQ values are provided and compared to the representative 15 WHO percentile periods. The calculated WHO 98th percentile corresponds to an OQ of 1.19, or 19% overweight. The WHO 84 percentile, 1 standard deviation above the mean, corresponds to an OQ of 1.07, just at the margin between Normal and Overweight categories (Table 1, columns 1 and 2). Analysis of the distribution of the 17,076 OQ values obtained from our data over the first 5 years of life demonstrated a symmetrical distribution. The percentage of OQs falling in each of the 5 general categories is comparable to the theoretical WHO percentages (Table 1, columns 5 and 6). In this comparison, the WHO distribution has a slightly larger percentage in the normal range and a slightly smaller percentage in the extremes.
Discussion The current practice of interpreting weight values in children is based on the observation of the relationship between height and weight at a specific age by calculating the child’s BMI. This value is then compared to a tabled value and the BMI percentile rank is then interpreted. Centers for Disease Control (CDC) growth
Table 1. Comparison of WHO Percentiles and Distribution With OQ Values. OQ ≥1.30 1.22 1.17 1.15 1.11 1.08 1.06 1.00 0.95 0.92 0.90 0.88 0.86 0.84 99 99 97 95 90 85 75 50 25 15 10 5 3 1
