What determines a healthy weight for a child?
Weight can mean a lot of things. Context is important, and different measurements are used for specific goals.
In the pediatric population, ideal and actual weights are used often to calculate growth patterns, medication dosing, and more. Perceptions of what weights are healthy for different children are where some variation comes into play.
Ideal body weight (IBW), body mass index (BMI), and other growth chart comparisons are all ways weight can be measured and compared in pediatric practice. The American Academy of Pediatrics (AAP) released new guidance on BMI goals and interpretations in regard to childhood obesity in 2023,1 but there are still a lot of questions about what kind of data should be considered when determining an ideal weight—or a healthy body weight for that matter—for a specific child.
Historically, the concept of IBW is based on height and weight tables originally published in the early 1900s, says Michelle H. Loy, MD, assistant professor, Weill Cornell Medicine/NewYork-Presbyterian Weill Cornell Medical Center in New York, New York. Since then, height and weight comparisons have been used to help quantify factors such as life expectancy, disease risk, and more. Clinically, IBW is an important tool used to calculate medication doses, nutrition, and other therapies, Loy explains. Although IBW and BMI are both tools that are commonly used in clinical practice, there is some debate about their accuracy in determining “healthy” weight compared with ideal weight or overall body mass.
“Because the formulas are designed to be applicable to a wide range of persons, they cannot be highly accurate for every single individual,” says Loy. “There is no single IBW for all individuals, and these calculators all have limitations. Factors such as fat-free body mass (muscle and bone) and level of sexual maturity for height can affect the IBW number.”
These caveats have raised concern from various stakeholders about how healthy weight in children is determined—especially after the AAP’s 2023 guidelines on obesity assessment and management were released.2,3 On one hand, nearly 20% of children and teenagers in the United States are considered obese.4 Obesity in childhood is linked to immediate health problems, as well as increased health risks later in life. On the other hand, ideal calculations of body weight, body mass, and the assessment of obesity—body composition measurements using dual-energy x-ray—are costly and not always accessible. Therefore, BMI calculations are often utilized as a more practical and accessible tool that can be used in daily clinical practice, according to AAP.1 The academy recognizes the limitations of BMI measurements for quantifying weight status and trajectories, but also supports the use of these tools as a generally accurate assessment of body fat.
The AAP report defines being overweight as a BMI at or above the 85th percentile on growth charts from the CDC for age and sex. Obesity is defined as having a BMI at or above the 95th percentile, AAP reveals.1 The AAP report further goes on to discuss how these measurements can or should be used to guide both clinical care in terms of medication dosing and treatments, but also how they can be used to counsel patients and families on healthy weight management.
Meanwhile, disordered eating groups have called the intent of this report into question, suggesting that the guidelines focus too much on BMI calculations and weight loss goals instead of overall health.2,3 The National Association of Anorexia Nervosa and Associated Disorders (ANAD) estimates that between 9% and 16% of Americans have some form of eating disorder in their lifetime.5 Other research findings suggest that, as with obesity, rates of disordered eating are increasing—even in children. Overall, 1 report estimates that 1.4% of children and teenagers combined have some form of disordered eating, with the highest rates found in those aged 8 to 15 years.6 Data from other studies estimate that the global prevalence of disordered eating in children and teens can be as high as 22%.7
Even the CDC acknowledges the shortfalls of using BMI measurements to determine healthy weight, noting that there are clinical limitations because BMI is actually a calculation of excess body weight instead of excess body fat. BMI measurements do not differentiate between weight from fat versus muscle or bone, and do not consider body fat distribution. Factors that can influence weight such as age, sex, and ethnicity are also poorly represented in a BMI measurement, according to CDC.8
Some examples of how BMI can be skewed include the following8:
● Higher percentage of body fat in older adults than in younger adults with the same BMI
● Higher total body fat in women than in men
● Higher BMI in individuals with increased muscle mass
Ultimately, there is no perfect tool to practically assess ideal or healthy weight in clinical practice outside of calculations for medication and treatment dosing. Loy says pediatricians are better off interpreting BMI values relative for age and sex on an individual basis considering additional factors such as diet patterns, physical activity, and family history.
Anna Dufresne, RD, LDN, CDCES, a clinical dietician at La Rabida Children’s Hospital in Chicago, Illinois, confirms the importance of a personalized approach when it comes to determining ideal and healthy weights. “Growth charts provide a helpful starting point, but aren’t the end-all-be-all when it comes to providing nutrition recommendations,” she says.
Even CDC and World Health Organization (WHO) growth charts are based on older data from the 1970s, Dufresne explains, and data on infants 12 months of age and younger were not included in early versions of the charts. When growth data for younger infants were included, they were based on a very limited demographic, she says.
When it comes to determining IBW, Dufresne recommends using the following charts for reference:
Use WHO growth tables for infants 24 months or younger.
Use CDC growth tables for children aged 2 years and up.
Certain medical conditions and genetic disorders have specific growth charts, she adds. Examples of conditions where these specialized growth charts should be used include the following:
● Cerebral palsy
● Wolf-Hirschhorn syndrome
● Down syndrome
● Cornelia de Lange syndrome
● Achondroplasia
To calculate the actual IBW, Dufresne offers the following equations:
Younger than 24 months: use weight for length at 50th percentile.
2 years or older or those on specialty growth charts: use (height/100)2 x BMI at 50th percentile.
Percentiles are the most common measurement for calculating IBW, but z-scores may be more accurate, she adds. If z-scores are used, Dufresne says the following equations would apply:
● Weight-for-length percentile (WHO): z-score, –0.99 to 1.72
● 3rd to 97th percentile is commonly used, but the 3rd percentile correlates to a z-score of –1.72
● BMI (CDC): z-score, –0.99 to 1.036
● 5th to 85th percentile is commonly used, but the 5th percentile correlates to a z-score of –1.65
● IBW: 90% to 110% of IBW
Additional considerations for applying IBW calculations in a healthy body weight assessment include factors related to gestational age at birth, body composition, and more, Dufresne says. The following may require modifications to these factors:
Prematurity: Calculate corrected gestational age for children born before 37 weeks for assessing anthropometrics and daily nutrition needs until the age of 2 years.
Macrocephaly: Skews weight upward and can mask underweight status.
Microcephaly: Skews weight downward and can mask overweight status.
Ethnic differences: African Americans tend to have lower body fat percentages than Caucasians with the same BMI, whereas people from Asian ethnic groups have higher levels of body fat than Caucasians with the same BMI.9
Sexual maturity: Growth patterns vary by level of sexual maturity. For example, early-maturing girls are twice as likely as typical- or late-maturing girls to be classified as overweight.
Individual growth trends: How well a child’s growth patterns have followed normal growth curves are also important to consider, Dufresne says. Chronic malnutrition or disease-related factors can decrease increases in height, making weight status appear higher than it actually is.10
Amputations: IBW should be based on the amputation type and extent.
Paralysis: IBW should be adjusted by 5% to 15% for paraplegia and by 15% to 20% for tetraplegia. The cause of paralysis should also be a consideration, as weight changes would be different in a child recently paralyzed compared with a child paralyzed since birth.11
Genetics and personal preference should also be considered, she says. Different body shapes run in families and can impact body and bone mass. As far as preferences, some people feel more comfortable at higher or lower ends of the IBW range, and this should factor into calculations, she notes.
There is no black-and-white answer when it comes to how best to assess a healthy weight in children, but experts suggest that pediatricians should use a combination of standardized growth charts and individualized assessments to make recommendations for their patients.
Click here to read more from the January/February issue of Contemporary Pediatrics.
References
- Hampl SE, Hassink SG, Skinner AC, et al. Clinical practice guideline for the evaluation and treatment of children and adolescents with obesity. Pediatrics. 2023;151(2):e2022060640. doi:10.1542/peds.2022-060640
- Radde K. New child obesity guidance raises worries over the risk of eating disorders. NPR. Updated February 22, 2023. Accessed December 28, 2023.
https://www.npr.org/2023/02/15/1155521908/eating-disorder-obesity-guidance-risk-weight-loss - McCarthy C. New pediatric guidelines on obesity in children and teens. Harvard Health Publishing. January 24, 2023. Accessed December 28, 2023.
https://www.health.harvard.edu/blog/new-pediatric-guidelines-on-obesity-in-children-and-teens-202301242880 - Childhood obesity facts. CDC. Updated May 17, 2022. Accessed December 28, 2023.
https://www.cdc.gov/obesity/data/childhood.html - Eating disorder statistics. ANAD. Accessed December 28, 2023.
https://anad.org/eating-disorder-statistic/ - Rozzell K, Moon DY, Klimek P, Brown T, Blashill AJ. Prevalence of eating disorders among US children aged 9 to 10 years: data from the Adolescent Brain Cognitive Development (ABCD) Study. JAMA Pediatr. 2019;173(1):100-101. doi:10.1001/jamapediatrics.2018.3678
- López-Gil JF, García-Hermoso A, Smith L, et al. Global proportion of disordered eating in children and adolescents: a systematic review and meta-analysis. JAMA Pediatr. 2023;177(4):363-372. doi:10.1001/jamapediatrics.2022.5848
- Body mass index: considerations for practitioners. CDC. Accessed December 29, 2023.
https://www.cdc.gov/obesity/downloads/bmiforpactitioners.pdf - Huggins Salomon S. Why body mass index (BMI) can be problematic for the BIPOC community. Everyday Health. March 31, 2022. Accessed December 29, 2023.
https://www.everydayhealth.com/weight/why-body-mass-index-bmi-can-be-problematic-for-the-bipoc-community/#:~:text=For%2520some%2520members%2520of%2520Black,CDC)%2520and%2520many%2520health%2520researchers - Wang Y, Moreno LA, Caballero B, Cole TJ. Limitations of the current World Health Organization growth references for children and adolescents. Food Nutr Bull. 2006;27(4, suppl 5):S175-S188. doi:10.1177/15648265060274S502
- Weight – PCP information. The University of Alabama at Birmingham. Accessed December 29, 2023.
https://www.uab.edu/medicine/pcp-sci/pcp-resource-topics/weight
