• Physicians use Body Mass Index (BMI) charts to help assess and monitor growth in children.
  • The CDC recently announced a revised version of the children and adolescent BMI chart.
  • The new chart has been extended to cover higher BMI measurements of ‘severe obesity’.
  • According to CDC data, more than 4.5 million US kids and adolescents are considered severely obese.

Physicians have long used the Body Mass Index (BMI) chart to estimate whether an individual’s body composition and growth is ‘healthy’ compared to the wider population.

There are two charts, one for adults and one for children — and the Centers for Disease Control and Prevention (CDC) recently announced an update to the chart designed for those between 2 and 20 years old.

The revised chart has been extended to cover higher BMI measurements. This measure comes as the CDC said that in 2018 more than 4.5 million children and adolescents in the US were reported to have severe obesity.

“The new growth charts, coupled with high-quality treatment, can help optimize care for children with severe obesity” Dr. Karen Hacker, director of the CDC’s National Center for Chronic Disease Prevention and Health Promotion, said in a statement.

Before diving into the new changes, let’s take a quick look at what BMI charts are and how they work.

These charts take the height and weight of an individual to create a figure. This number is then compared to people of the same age and gender to gauge whether their overall body mass is considered ‘healthy’.

“Depending on where the child falls on the chart, a healthcare provider can quickly see if the child is underweight, in the ideal weight range, overweight, or obese,” explained Dr. David Berger, founder of Dr. David, MD and Wholistic Pediatrics & Family Care.

“The chart data is plotted based on percentiles, and the healthy range for BMI changes over age,” Berger shared with Healthline.

Percentiles are a method of grouping and ‘ranking’ for easier comparison. For instance, if a child’s BMI falls within the 60th percentile, it means that 60% of kids the same age had the same or lower BMI score.

How the children’s BMI chart has changed

The previous iteration of the chart, released in 2000, was based on data collected between 1963 and 1980, when levels of obesity among children were lower.

According to the CDC, a child is considered ‘obese’ if their BMI is higher than 95% of kids of the same gender and age. They are classed as ‘severely obese’ if their BMI is 120% higher than the 95th percentile.

“Under the previous charts, it was difficult to categorize the severity of obesity,” said Dr. Paula Newton, a pediatric endocrinologist with the University of Maryland Children’s Hospital and assistant professor at the University of Maryland School of Medicine.

“Everyone with a BMI over the 95th percentile was lumped together in the same category of ‘obese’,” she told Healthline — despite the fact “there are levels of severity.”

However, in the new chart, Newton explained, “there are expanded categories of ‘obese’.” It has also extended to BMI measurements up to 60 — whereas, previously, only BMIs up to 37 were covered.

The changes will allow medical professionals to monitor children better, said Dr. Elizabeth Davis, Pediatric Sports Medicine Physician at Orlando Health Arnold Palmer Hospital for Children.

Previously, she told Healthline, “there has been no way to accurately follow these children with higher BMIs. Now we have a way to do this.”

Furthermore, she added, the new charts “should give us more data for research in following these children over time.”

Only the upper end of the BMI scale has changed, with the categories of ‘underweight’, ‘normal weight’, and ‘overweight’ remaining the same as the previous version. As such, the CDC advises doctors can still use the old chart for children who are not considered obese.

While BMI charts are widely used, they’ve also been greatly debated. In some respects, the tool is certainly a helpful form of guidance.

“BMI growth charts serve a role for overall growth tracking during childhood and adolescence, and can be useful to know when to screen for potential health problems such as diabetes and high blood pressure,” stated Davis.

Berger revealed they can also help doctors recognize emerging patterns. “It is helpful to look at the trend of the BMI (as well as the height and weight growth curves) over time to see how things are changing.”

Dr. Ilan Shapiro, chief health correspondent and medical affairs officer at AltaMed Health Services, agreed.

“BMI is a general measure of how we can inform families and our communities to better address what is happening,” he told Healthline.

However, Shapiro continued, the charts are “not the most efficient way to measure health.”

A key issue is that the charts do not consider the role of muscle mass. This is a ‘good’ type of weight, yet BMI doesn’t differentiate between this and fat when calculating overall weight.

“Muscle weighs more than fat,” Berger explained. “So, especially for adolescents who are athletes, the BMI could be higher compared to a child of the same weight who is not in shape.”

Ethnic background and genetics can also play a role in physique, revealed Berger — yet the BMI charts do not factor this in. “The current charts do not differentiate, so it might not be appropriate to compare a Pacific Islander to someone from Asia, for example,” he stated.

Crucially, BMI also does not account for social and economic impacts and influences.

“We need to ask questions about what is happening at school, who the primary caregiver is, [if there] is food scarcity, and consider cultural beliefs connected to food consumption,” noted Shapiro. Engagement and information, he said, are far more significant than simply reviewing a number.

Newton agreed that, if necessary, a BMI should act as a starting point for investigations and recommendations.

“If I saw a child who was previously at the 80th percentile for BMI and they were experiencing rapid weight gain and an increasing BMI … I would ask more questions,” she stated.

“Additional information I would gather includes family history, the child’s eating habits, access to healthy foods, neighborhood safety, home environment, physical activity, mental health, and so on,” Newton shared.

Rates of obesity are increasing among the child and adolescent populations in the US. Now the CDC has revised the BMI chart for those aged 2-20 to reflect different levels of severe obesity. The adjustments allow clinicians greater scope for monitoring the growth of severely obese children and screening for health concerns.

BMI charts are “an easy tool for healthcare professionals to monitor an individual child’s growth over time,” said Jennifer House, MSc, RD, founder of First Step Nutrition. However, they should not be used as the sole means of assessing overall health and physique.

BMI charts have faced criticism in the past. Experts point out they do not consider other important factors, such as genetics or muscle mass.

“There are a lot of reasons someone may be obese,” House stated. Furthermore, she added, they can also be used to shame or blame a child or their family, which only exacerbates the problem.

Ultimately, House explained, we need to look at the bigger picture in tackling childhood obesity. “How can we support the family with cooking, having healthy foods available, and raising children to have a healthy relationship with food?”

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